Synthesis of New C- and N-β-d-Glucopyranosyl Derivatives of Imidazole, 1,2,3-Triazole and Tetrazole, and Their Evaluation as Inhibitors of Glycogen Phosphorylase.

The aim of the present study was to broaden the structure-activity relationships of C- and N-β-d-glucopyranosyl azole type inhibitors of glycogen phosphorylase. 1-Aryl-4-β-d-gluco-pyranosyl-1,2,3-triazoles were prepared by copper catalyzed azide-alkyne cycloadditions between O-perbenzylated or O-peracetylated β-d-glucopyranosyl ethynes and aryl azides. 1-β-d-Gluco-pyranosyl-4-phenyl imidazole was obtained in a glycosylation of 4(5)-phenylimidazole with O-peracetylated α-d-glucopyranosyl bromide. C-β-d-Glucopyranosyl-N-substituted-tetrazoles were synthesized by alkylation/arylation of O-perbenzoylated 5-β-d-glucopyranosyl-tetrazole or from a 2,6-anhydroheptose tosylhydrazone and arenediazonium salts. 5-Substituted tetrazoles were glycosylated by O-peracetylated α-d-glucopyranosyl bromide to give N-β-d-glucopyranosyl-C-substituted-tetrazoles. Standard deprotections gave test compounds which were assayed against rabbit muscle glycogen phosphorylase b. Most of the compounds proved inactive, the best inhibitor was 2-β-d-glucopyranosyl-5-phenyltetrazole (IC50 600 μM). These studies extended the structure-activity relationships of β-d-glucopyranosyl azole type inhibitors and revealed the extreme sensitivity of such type of inhibitors towards the structure of the azole moiety.

1. Introduction

Glycogen phosphorylase inhibitors (GPIs) attract considerable scientific interest [1,2,3] since such compounds may be applied in finding new therapies against type two diabetes [4,5,6], myocardial [7,8] and cerebral [9,10] ischemias, and tumors [11,12,13,14,15,16]. In addition to demonstrating in vivo antihyperglycemic activities [17,18,19,20,21], physiological studies with several GPIs revealed unprecedented effects on hepatic metabolism [22] and improvement of pancreatic β-cell function [23].

A large variety of compounds have been designed and synthesized for the inhibition of GP [24,25]. Among them different derivatives of d-glucose represent the largest class of inhibitors. Within glucose-derived compounds N-acyl-β-d-glucopyranosylamines (I in Table 1) [26,27,28,29] were among the first low micromolar inhibitors of rabbit muscle GP b (RMGPb), the prototype of these enzymes [30]. Based on the concept of bioisosterism [31,32,33] many sorts of N- and C-β-d-gluco-pyranosyl heterocycles, wherein the hetero-ring replaced the NHCO moiety of I as its bioisostere, were synthesized and tested against RMGPb. Thus, N-β-d-glucopyranosyl 1,2,3-triazoles II [29,34] had comparable inhibitory effects to those of amides I. Among C-β-d-glucopyranosyl derivatives three isomeric oxadiazoles III–V were studied to show that the constitution of the heterocycle had a decisive bearing on the efficiency. Thus, 1,3,4-oxadiazoles III [35,36,37] proved to be rather weak inhibitors, the 3-glucosyl-5-substituted isomers IV [38] were somewhat more efficient (especially the 2-naphthyl derivative IVc) and the 5-glucosyl-3-substituted counterparts V [37,39] showed low micromolar inhibition. C-Glucosyl 1,2,4-triazoles VI [40,41] and imidazoles VII [42,43] featuring hydrogen bond donor heterocycles were significantly more effective.

Table 1

Selected glucose derived inhibitors of rabbit muscle glycogen phosphorylase b (Ki [μM]).

R					CH3
					a		b		c
I					32 [26]		81 [26]144 [27]		10 [28]13 [29]
II					-		151 [29]162 [34]		16 [29]36 [34]
III					212 [35]145 [36]		10% at 625 μM [37]		10% at 625 μM [37]
IV					No inh. at 625 μM [38]		10% at 625 μM [38]		38 [38]
V					-		27 [39]64 [37]		12 * [37]
VI					499 [41]		7 [40,41]		0.41 [40,41]
VII					-		0.28 [42,43]		0.031 [42,43]
VIII					No inh. at 625 μM [35]
* A Ki value of 2.4 μM was measured by N.G. Oikonomakos et al. (unpublished results in ref. [37])
Target compounds in this study:
IX			X			XI			XII

Actually, these compounds are the best glucose analogue inhibitors of GP known to date. Their efficiency, among other factors, is due to the formation of a H-bridge between the heterocycle and the His-377 main chain carbonyl group in the active site of the enzyme. 5-Glucosyltetrazole VIII [35], although capable of H-bond formation, proved inactive. It is remarkable that, besides the properties of the heterocycle, also the nature and the size of the substituent of the azole moiety had a very significant influence on the activity of the inhibitors. While methyl substituted derivatives in column a were practically inactive, a phenyl appendage (column b) made much more efficient compounds and the 2-naphthyl derivatives (column c) proved to be the strongest inhibitors. With these preliminaries in mind, in order to make the structure-activity relationship of N- and C-β-d-glucopyranosyl azole type compounds more complete, we envisaged to synthesize the “missing” counterparts of the above glucose derivatives. In this paper the syntheses and enzymatic evaluation of 4-β-d-glucopyranosyl-1-substituted-1,2,3-triazoles IX, 1-β-d-glucopyranosyl-4-substituted imidazoles X, 5-β-d-glucopyranosyl-2-substituted tetrazoles XI, and 2-β-d-glucopyranosyl-5-substituted tetrazoles XII are presented.

2. Results and Discussion

For the syntheses of C-glucosyl 1,2,3-triazoles of type IX several methods were published and this chemistry was reviewed last year [44]. Our work, summarized in Table 2, started with O-perbenzylated C-glucosyl acetylene 1 described in the literature [45]. Copper catalyzed azide-alkyne cycloaddition (CuAAC) [46] was effected from 1 either by pre-formed aryl azides with CuO(CO)C3H7(PPh3)2 as the catalyst [47] (method a) or azides obtained in situ from areneboronic acids [48,49] (method b) to give 1,2,3-triazoles 2a–c in very good yields. Removal of the O-benzyl protecting groups from 2a by usual catalytic hydrogenation (method c) gave excellent yield of 5a, however, under the same conditions 2c gave an inseparable product mixture. After O-peracetylation (method e) of the mixture the products could be separated and identified as 4c and a partially saturated derivative 4d. Since the formation of a tetrahydronaphthyl by-product under catalytic hydrogenation was observed previously with a 2-naphthyl substituted C-glucopyranosyl 1,2,4-triazole [50] hydrogenolytic deprotection of 2b was not attempted. Instead, the protecting groups were exchanged to acetate esters as reported to get O-peracetylated acetylene 3 [. CuAAC from 3 produced triazoles 4b and 4c in very good yields. Formation of 4b was also effected from 2b by a direct exchange of protective groups by method d [51]. Removal of the O-acetyl groups from 4b,c under Zemplén conditions (method f) gave the targeted 5b,c in excellent yields.

Table 2

Synthesis of 1-aryl-4-(β-d-glucopyranosyl)-1,2,3-triazoles.

Reagents and conditions: (a) ArN3, CuO(CO)C3H7(PPh3)2, dry CH2Cl2, r.t.; (b) і. ArB(OH)2, NaN3, CuSO4·5H2O, MeOH, r.t., іі. 1 or 3, L-ascorbic acid, CH2Cl2-H2O (1:1), 50 °C; (c) H2, Pd(C), dry EtOH, dry EtOAc, r.t.; (d) TMSOTf, Ac2O, −40 °C; (e) і. H2, Pd(C), dry EtOAc, dry MeOH, 40 °C, іі. Ac2O, pyridine, 90 °C; (f) ~1M NaOMe in MeOH, r.t.
Ar		Conditions and Yields (%)
			2		4		5
a		a	78 (from 1)	-	-	c	92 (from 2a)
b		b	79 (from 1)	d	68 (from 2b)	f	96 (from 4b)
				b	80 (from 3)
c		a	85 (from 1)	e	29 (from 2c)	f	94 (from 4c)
				a	91 (from 3)
d		-	-	e	3 (from 2c)	-	-

For the preparation of an imidazole of type X a literature method [52] was adapted. Thus, acetobromoglucose 6 was reacted with 4-phenyl-imidazole in the presence of Hg(CN)2 in acetonitrile to give 1-glucopyranosyl-4-phenyl-imidazole 7 (Scheme 1). Due to the tautomerism of imidazoles the formation of the isomeric 1-glucopyranosyl-5-phenyl-imidazole would also be possible, however, this was excluded on the basis of a HMBC measurement. Specifically, the observation of cross peaks between H-1’–C-2, H-1’‒C-5, C-1’‒H-2, and C-1’‒H-5 clearly indicated the formation of 7. O-Deacetylation of 7 by the Zemplén method gave 8 in good yield.

Scheme 1

Synthesis of 1-(β-d-glucopyranosyl)-4-phenyl-imidazole.

Next we turned to the synthesis of C-glucopyranosyl tetrazoles of type XI. While 5-(β-d-gluco-pyranosyl)tetrazoles (e.g., 9) are long known compounds ([35,49] and references cited therein), no N-substituted derivatives could be located in the literature. For the preparation of the phenyl substituted derivatives a copper catalyzed reaction [53] of 9 and benzeneboronic acid was applied (Table 3, conditions a). Although the tautomerism of the tetrazole moiety could have facilitated the formation of regioisomers, only 10a was obtained in excellent yield as it was claimed in the cited paper. By modifying a literature procedure [54], compound 10a was also prepared, albeit in lower yield, from tosylhydrazone 12 [55,56] and benzenediazonium tetrafluoroborate [57,58] (conditions c). For the methylation of 9 a method [59] applied for the synthesis of C-glycofuranosyl tetrazoles was adapted. Thus, 9 was reacted with diazomethane to give a 1:1 mixture of the regioisomeric tetrazoles 10e and 11e in very good overall yield (conditions b). Removal of the ester protecting groups by the Zemplén protocol gave the test compounds 13 and 14 in very good yields (conditions d). The regioisomers of the formed C,N-disubstituted tetrazoles could easily be identified by the 13C-NMR signal of the C-5 carbons. It is well known that the tetrazole carbon of 2,5-disubstituted derivatives (162–167 ppm) is shifted downfield by ~10 ppm in comparison to that of the 1,5-disubstituted counterparts (152–156 ppm) [60], and this is clearly visible in the obtained data shown in Table 3. In addition, for 11e 1H-1H NOEs were observed between the CH3 protons and the pyranose H-1’ and H-2’, while for 10e the NOE spectrum did not indicate proximity between the substituents of the tetrazole.

Table 3

Synthesis of 5-(β-d-glucopyranosyl)-N-substituted-tetrazoles.

Reagents and conditions: (a) R’B(OH)2, CuCl2, TMEDA, K2CO3, dry CH2Cl2, r.t.; (b) CH2N2 in Et2O, dry CH2Cl2, r.t.; (c) PhN2BF4, dry pyridine, −40 °C; (d) ~1M NaOMe in MeOH, r.t.
		Conditions, Yields (%) and Chemical Shifts (ppm) for Tetrazole C-5 (Solvent)
R’			10		11			13		14
a	Phenyl	a	95	162.2(CDCl3)	-	-	d	94	164.8(DMSO-d6)	-	-
		c	61		-
e	Methyl	b	38	162.1(CDCl3)	38	149.9(CDCl3)	d	72	163.9(D2O)	97	153.9(D2O)

For the synthesis of N-(β-d-glucopyranosyl)-5-substituted-tetrazoles a literature protocol was applied to give 15a and 16a [61] in the reaction of acetobromoglucose 6 and 5-phenyltetrazole [62] (Table 4). From a similar transformation of 6 with 5-methyltetrazole [62] only the 2,5-disubstituted 15e could be isolated in moderate yield and the formation of the HBr elimination product 2-acetoxy-d-glucal 17 was observed in a significant amount. Protecting group removal was effected by the Zemplén method to furnish the test compounds 18 and 19 in very good yields. The regioisomeric tetrazoles 15, 18 vs. 16, 19 were identified on the basis of the C-5 chemical shifts as described above (see respective data in Table 4).

Table 4

Synthesis of N-(β-d-glucopyranosyl)-5-substituted-tetrazoles.

Reagents and conditions: (a) K2CO3, 4 Å molecular sieves, dry acetone, reflux; (b) ~1 M NaOMe in MeOH, r.t.
R’		Conditions, Yields (%) and Chemical Shifts (ppm) for Tetrazole C-5 (Solvent)
			15		16		17		18		19
a	Phenyl	a	79	165.8(CDCl3)	17	155.9(CDCl3)	-	b	85	165.9(D2O)	86	157.3(D2O)
e	Methyl	a	26	163.9(CDCl3)	-		45	b	84	164.7(D2O)	-

The new compounds were assayed against rabbit muscle glycogen phosphorylase b enzyme (RMGPb) as described earlier [27] and the results are collected in Table 5. The inefficiency of C-glucopyranosyl 1,2,3-triazoles 5 (entries 4–6) as compared to the micromolar inhibition of the N-glucopyranosyl counterparts II in Table 2 came as a surprise, since the size of the heterocycle and the position of the H-bond donor and acceptor sites of the ring must not have been altered by the interchange of the substituents. A comparison of the inhibitory efficiency of N-benzoyl-β-d-gluco-pyranosylamine Ib (entry 1) with its “reversed” counterpart N-phenyl-2,6-anhydro-d-glycero-d-gulo-heptonamide 20 (shown in entry 3) results in a ratio of 38–67 (~53 as an average). Multiplication of the inhibition constants of IIb (entry 2) with this average factor to predict the efficiency of 5a (entry 4) gives values of ~7900–8500 μM, a range being well beyond the concentrations investigated in this study (max 625 μM). Nevertheless, our observations may refer to a strong directionality in the amide-1,2,3-triazole bioisosterism (mostly ignored in related studies [63,64]) indicating that the proper replacement must correspond to the pairs Ib–IIb and 20–5a in entries 1–2 and 3–4, respectively.

Table 5

Inhibitory effect of the new and some earlier compounds against rabbit muscle glycogen phosphorylase b (RMGPb).

Entry	Compound		Inhibition * (μM)
1.	Ib		Ki 81 [26]Ki 144 [27]
2.	IIb		Ki 151 [29]Ki 162 [34]
3.	20		Ki 5400 [65]
4.	5a		N.I.
5.	5b		N.I.
6.	5c		N.I.
7.	8		N.I.
8.	13a		N.I.
9.	13e		N.I.
10.	14e		N.I.
11.	18a		IC50 600 (calculated ** Ki 327)
12.	18e		N.I.
13.	19a		N.I.

* N.I. no inhibition at 625 μM concentration; ** Calculated by the Cheng-Prusoff equation [66].

N-Glucosylimidazole 8 (entry 7) as well as N-substituted-5-glucopyranosyltetrazoles 13 and 14 (entries 8–10) proved non-inhibitory in the investigated concentration range. From the N-glucopyranosyl-5-substituted tetrazoles 18 and 19 (entries 11–13) only the 5-phenyl derivative 18a showed very weak inhibition (entry 11). This study has corroborated that the inhibition of glycogen phosphorylase by N- and C-glucopyranosyl azole type compounds is extremely sensitive to the properties of the heterocycle.

3. Experimental

3.1. General Methods

Anhydrous solvents were prepared by standard methods. CH2Cl2, CHCl3 and EtOAc were distilled from P4O10 and stored over 4 Å molecular sieves. MeOH was distilled over Mg turnings and iodine. Acetone was dried by distillation from CaSO4. Anhydrous pyridine (VWR, Vienna, Austia) and EtOH (Molar Chemicals, Halásztelek, Hungary) were used as received. Melting points were measured on a Kofler hot stage and are uncorrected. Optical rotations were determined on a P-2000 polarimeter (Jasco, Easton, MD, USA) at room temperature. NMR spectra were recorded with DRX360 (360/90 MHz for 1H/13C) and DRX400 (400/100 MHz for 1H/13C) spectrometers (Bruker, Karlsruhe, Germany). Chemical shifts are referenced to internal Me4Si (1H) or the residual solvent signal (13C). HRMS spectra were recorded with a Bruker maXis II spectrometer with electrospray ionization technique. TLC was performed on DC Alurolle Kieselgel 60 F254 (Merck, Darmstadt, Germany), the plates were visualized by gentle heating. For column chromatography Kieselgel 60, 63–200 µm (Molar Chemicals) was used. Organic solutions were dried over anhydrous MgSO4 and concentrated in vacuo at 40–50 °C (water bath). Alkynes 1 [45] and 3 [51], tetrazole 9 [49], tosylhydrazone 12 [55,56], 5-phenyltetrazole [62], 5-methyltetrazole [62], and benzenediazonium tetrafluoroborate [57,58] were prepared according to literature procedures.

3.1.1. General Procedure 1 for the Synthesis of O-Peracetylated or O-Perbenzylated 1-aryl-4-β-d-Glucopyranosyl-1,2,3-triazoles from Azido-Arenes

To the solution of the corresponding alkyne (1 or 3) in anhydr. CH2Cl2 (0.1 mmol/mL) the azido-arene and CuO(CO)C3H7(PPh3)2 were added and the mixture was stirred at rt for the given time (20 min–5 h) while the reaction was monitored by TLC (eluent: hexane-EtOAc 4:1 for O-benzylated cmpounds, 1:1 for O-acetylated compounds). After total consumption of the alkyne the solvent was evaporated and the residue purified by column chromatography.

3.1.2. General Procedure 2 for the Synthesis of O-Peracetylated or O-Perbenzylated 1-aryl-4-β-d-Glucopyranosyl-1,2,3-triazoles from Arylboronic Acids by Using CuSO4/L-Ascorbic Acid Catalytic System

Arylboronic acid (1 equiv.) was dissolved in MeOH (5 mL/mmol), NaN3 (1.2 equiv.) and CuSO4·5H2O (0.1 equiv.) were added and the reaction mixture was stirred at r.t. After 18 h distilled water (10 mL/mmol), CH2Cl2 (10 mL/mmol), the corresponding alkyne (1 or 3, 0.3 equiv.) and L-ascorbic acid (0.5 equiv.) was added and the mixture was stirred at 50 °C (oil bath temp.). When TLC showed complete disappearance of the alkyne (eluent: hexane-EtOAc 4:1 for O-benzylated compounds, 1:1 for O-acetylated compounds) the mixture was diluted with CH2Cl2 and water. After separation of the phases the aqueous layer was washed with CH2Cl2. The combined organic phases were dried, concentrated under reduced pressure and chromatographed to yield the pure 1,2,3-triazole.

3.1.3. General Procedure 3 for Removal of the O-Acetyl Protecting Groups

An O-acyl protected compound (100 mg) was dissolved in anhydr. MeOH (5 mL), a few drops of ~1 M solution of NaOMe/MeOH was added and the mixture was left to stand at r.t. After complete conversion (TLC monitoring, CHCl3-MeOH 7:3) the reaction mixture was neutralized with Amberlyst 15 (hydrogen form). After removal of the resin by filtration, the solvent was evaporated in vacuo and the crude product was purified by column chromatography (CHCl3-MeOH 9:1).

3.1.4. General Procedure 4 for the Synthesis of O-Peracetylated N-(β-d-Glucopyranosyl)tetrazoles

Freshly flame dried K2CO3 (10 equiv., 1.68 g, 12.2 mmol), 4 Å powdered molecular sieves (500 mg), 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide (6, 500 mg, 1.22 mmol) and a 5-substituted tetrazole (2 equiv., 2.44 mmol) were mixed in a round bottom flask, anhydr. acetone (15 mL) was added and the mixture was stirred and refluxed for 8 h. After removal of the solids by filtration the filtrate was concentrated under reduced pressure and chromatographed to give N-(β-d-glucopyranosyl)tetrazoles.

3.2. Characterization of the Comounds

1-Phenyl-4-(2′,3′,4′,6′-tetra-O-benzyl-β- (2a). Prepared according to general procedure 1 from alkyne 1 (153 mg, 0.28 mmol), azidobenzene (33 mg, 0.28 mmol) and CuO(CO)C3H7(PPh3)2 (2 mg, 0.003 mmol). Reaction time: 20 min. Purified by column chromatography (eluent: hexane-EtOAc = 4:1 → 2:1 gradient) to yield 145 mg (78%) white crystals. Rf = 0.56 (hexane-EtOAc = 2:1); Mp: 160–162 °C; [α]D = −16 (c 0.53, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 7.81 (1H, s, triazole H-5), 7.66–6.99 (25H, m, Ar), 4.98, 4.93 (2 × 1H, 2 d, J = 11.1 Hz, PhCH2), 4.88, 4.60 (2 × 1H, 2 d, J = 10.7 Hz, PhCH2), 4.69, 4.40 (2 × 1H, 2d, J = 10.9 Hz, PhCH2), 4.57, 4.52 (2 × 1H, 2d, J = 12.1 Hz, PhCH2), 4.61 (1H, d, J = 9.6 Hz, H-1’), 3.98, 3.86 (2H, 2 pseudo t, J = 9.4, 8.8 Hz, H-2’ and/or H-3’ and/or H-4’), 3.79–3.70 (3H, m, H-2’ or H-3’ or H-4’, H-6’a, H-6’b), 3.66 (1H, ddd, J = 9.4, 3.5, 2.4 Hz, H-5’); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 146.4 (C-4), 138.5–136.9 (Ar), 129.6–127.5 (Ar), 120.9 (triazole C-5), 120.4 (Ar), 86.9, 81.5, 79.4, 78.1, 74.0 (C-1’–C-5’), 75.5, 75.0, 74.7, 73.4 (4 × PhCH2), 69.0 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C42H42N3O5+ ([M + H]+): 668.3119. Found: 668.3116.

1-(Naphthalen-2-yl)-4-(2′,3′,4′,6′-tetra-O-benzyl-β- (2b). Prepared according to general procedure 2 from 2-naphthylboronic acid (52 mg, 0.30 mmol), CuSO4·5H2O (8 mg, 0.03 mmol), NaN3 (24 mg, 0.36 mmol), L-ascorbic acid (27 mg, 0.15 mmol) and alkyne 2 (50 mg, 0.09 mmol). Reaction time: 1.5 h. Purified by column chromaography (EtOAc-hexane 1:7 → 1:6 gradient) to yield 52 mg (79%) white crystalline product. Rf = 0.23 (hexane-EtOAc = 4:1); Op: 140–141 °C; [α]D = −19 (c 0.52, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 8.07–7.81 (5H, m, Ar), 7.92 (1H, s, triazole H-5), 7.59–7.53 (2H, m, Ar), 7.38–7.01 (20H, m, Ar), 4.99, 4.95 (2 × 1H, 2 d, J = 11.1 Hz, PhCH2), 4.88, 4.61 (2 × 1H, 2 d, J = 10.7 Hz, PhCH2), 4.71, 4.44 (2 × 1H, 2 d, J = 10.9 Hz, PhCH2), 4.59, 4.53 (2 × 1H, 2 d, J = 12.2 Hz, PhCH2), 4.65 (1H, d, J = 9.7 Hz, H-1’), 3.99, 3.88 (2H, 2 pseudo t, J = 9.4, 8.8 Hz, H-2’ and/or H-3’ and/or H-4’), 3.81–3.72 (3H, m, H-2’ or H-3’ or H-4’, H-6’a, H-6’b), 3.68 (1H, ddd, J = 9.4, 3.5, 1.3 Hz, H-5’); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 146.4 (triazole C-4), 138.5–132.8 (Ar), 129.9–126.9 (Ar), 121.1 (triazole C-5), 118.9, 118.4 (Ar), 87.0, 81.4, 79.5, 78.2, 74.1 (C-1’–C-5’), 75.6, 75.1, 74.7, 73.4 (4 × PhCH2), 69.1 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C46H44N3O5+ ([M + H]+): 718.3275. Found: 718.3273.

1-(Naphthalen-1-yl)-4-(2’,3’,4’,6’-tetra-O-benzyl-β- (2c). Prepared according to General procedure 1 from alkyne 2 (150 mg, 0.27 mmol), 1-azidonaphthalene (46 mg, 0.27 mmol) and CuO(CO)C3H7(PPh3)2 (2 mg, 0.003 mmol). Reaction time: 4 h. Purified by column chromatography (eluent: hexane-EtOAc = 4:1) to yield 167 mg (85%) brown amorphous solid. Rf = 0.13 (EtOAc-hexane = 1:4); [α]D = −2 (c 0.53, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 7.92–7.89 (2H, m, Ar), 7.86 (1H, s, triazole H-5), 7.55-7.07 (25H, m, Ar), 4.99, 4.95 (2 × 1H, 2 d, J = 11.1 Hz, PhCH2), 4.89, 4.61 (2 × 1H, 2 d, J = 10.7 Hz, PhCH2), 4.79, 4.49 (2 × 1H, 2 d, J = 10.7 Hz, PhCH2), 4.59, 4.54 (2 × 1H, 2 d, J = 12.2 Hz, PhCH2), 4.70 (1H, d, J = 9.8 Hz, H-1’), 4.16, 3.90 (2H, 2 pseudo t, J = 9.4, 8.9 Hz, H-2’ and/or H-3’ and/or H-4’), 3.83–3.70 (4H, m, H-2’ or H-3’ or H-4’, H-5’, H-6’a, H-6’b); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 145.2 (triazole C-4), 138.4–122.1 (Ar), 125.7 (triazole C-5), 86.4, 81.6, 79.4, 78.1, 73.8 (C-1’–C-5’), 75.5, 75.0, 74.9, 73.3 (4 × PhCH2), 69.0 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C46H44N3O5+ ([M + H]+): 718.3275. Found: 718.3270.

1-(Naphthalen-2-yl)-4-(2’,3’,4’,6’-tetra-O-acetyl-β- (4b). Method A: To the solution of 2b (106 mg, 0.15 mmol) in anhydr. CH2Cl2 (4 mL) and acetic anhydride (4 mL) trimethylsilyl trifluoromethanesulfonate (214 μL, 1.18 mmol) was added at −40 °C. The mixture was slowly allowed to warm up and stirred at r.t. for 24 h, then at 50 °C for 24 h. Saturated aqueous NaHCO3 (2 mL) was added to the reaction mixture at 0 °C and the mixture was extracted with CH2Cl2 (3 × 5 mL). The combined organic phases were dried, concentrated and purified by column chromatography (hexane-EtOAc 2:1) to yield 53 mg (68%) product.

Method B: Prepared according to general procedure 2 from 2-naphthylboronic acid (80 mg, 0.47 mmol), CuSO4·5H2O (12 mg, 0.05 mmol), NaN3 (36 mg, 0.56 mmol), L-ascorbic acid (41 mg, 0.23 mmol) and 3 (50 mg, 0.14 mmol). Reaction time: 1.5 h. Purified by column chromatography (eluent: hexane-CH2Cl2-EtOAc 5:4:1) to yield 59 mg (80%) product.

White crystals. Rf = 0.31 (hexane-EtOAc 1:1); Mp: 225–227 °C; [α]D = −71 (c 0.54, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 8.19 (1H, s, triazole H-5), 8.16 (1H, s, Ar), 8.01–7.85 (4H, m, Ar), 7.59–7.57 (2H, m, Ar), 5.45–5.38 (2H, m, H-2’ and/or H-3’ and/or H-4’), 5.23 (1H, pseudo t, J = 9.7, 9.5 Hz, H-2’ or H-3’ or H-4’), 4.90 (1H, d, J = 9.6 Hz, H-1’), 4.33 (1H, dd, J = 12.4, 4.9 Hz, H-6’a), 4.17 (1H, dd, J = 12.4, 1.4 Hz, H-6’b), 3.94 (1H, ddd, J = 9.9, 4.7, 1.6 Hz, H-5’), 2.09, 2.08, 2.04, 1.96 (4 × 3H, 4 s, CH3CO); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 170.6, 170.1, 169.6, 169.5 (CH3CO), 144.9 (C-4), 134.1, 133.1, 132.9, 129.9, 128.2, 127.9, 127.5, 127.0, 118.8 (Ar), 120.6 (C-5), 76.3, 73.9, 73.2, 71.2, 68.4 (C-1’–C-5’), 62.1 (C-6’), 20.7 (CH3CO), 20.6 (3 × CH3CO). ESI-HRMS positive mode (m/z): calcd. for C26H27N3NaO9+ ([M + Na]+ ): 548.1640. Found: 548.1636.

1-(Naphthalen-1-yl)-4-(2’,3’,4’,6’-tetra-O-acetyl-β- (4c) and 1-(5,6,7,8-n class="Species">tetrahydronaphthalen-1-yl)-4-(2’,3’,4’,6’-tetra-O-acetyl-β- (4d)

Method A: To the solution of 1-(naphthalen-1-yl)-4-(2’,3’,4’,6’-tetra-O-benzyl-β-d-glucopyranosyl)-1H-1,2,3-triazole (2c, 159 mg, 0.22 mmol) in anhydr. EtOAc (5 mL) Pd(C) (10 wt. %, 16 mg) was added and the mixture was stirred in H2 atmosphere (1 bar) at 40 °C for 5 h. The catalyst was removed by filtration and the filtrate was concentrated and the residue was dissolved in pyridine (2.5 mL) and acetic anhydride (1 mL) and kept at 90 °C for 3 h. After evaporation the products were separated by column chromatography (hexane-EtOAc 2:1) to yield 4c (34 mg, 29%) and 4d (3 mg, 3%).

Method B: Compound 4c was prepared according to general procedure 1 from alkyne 3 (50 mg, 0.14 mmol), 1-azidonaphthalene (15 mg, 0.14 mmol) and CuO(CO)C3H7(PPh3)2 (0.6 mg, 0.001 mmol). Reaction time: 5 h. Isolation by column chromatography (hexane-EtOAc 2:1 → 1:1 gradient) yielded 4c (67 mg, 91%).

4c: white crystals. Rf = 0.30 (hexane-EtOAc = 1:1); Mp: 195–197 °C; [α]D = −29 (c 0.5, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 8.00 (1H, s, triazole H-5), 8.04–7.97 (2H, m, Ar), 7.60–7.55 (5H, m, Ar), 5.47–5.38 (2H, m, H-2’ and/or H-3’ and/or H-4’), 5.23 (1H, pseudo t, J = 9.7, 9.3 Hz, H-2’ or H-3’ or H-4’), 4.94 (1H, d, J = 9.4 Hz, H-1’), 4.32 (1H, dd, J = 12.5, 4.8 Hz, H-6’a), 4.18 (1H, dd, J = 12.5, 1.8 Hz, H-6’b), 3.95 (1H, ddd, J = 9.9, 4.7, 1.8 Hz, H-5’), 2.09, 2.07, 2.04, 1.99 (4 × 3H, 4 s, CH3CO); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 170.6, 170.1, 169.6, 169.5 (CH3CO), 144.1 (triazole C-4), 134.1, 133.4, 130.5, 128.4, 128.2, 127.9, 127.0, 124.9, 123.6, 122.1 (Ar), 125.0 (triazole C-5), 76.3, 73.9, 73.4, 71.4, 68.4 (C-1’–C-5’), 62.1 (C-6’), 20.7 (CH3CO), 20.6 (3 × CH3CO). ESI-HRMS positive mode (m/z): calcd. for C26H27N3NaO9+ ([M + Na]+): 548.1640. Found: 548.1639.

4d: colouress syrup. Rf = 0.40 (hexane-EtOAc 1:1); [α]D = −49 (c 0.15, CHCl3); 1H-NMR (CDCl3, 360 MHz) δ (ppm): 7.75 (1H, s, H-5), 7.26–7.22 (2H, m, Ar), 7.12 (1H, m, Ar), 5.42–5.33 (2H, m, H-2’ and/or H-3’ and/or H-4’), 5.21 (1H, pseudo t, J = 9.6, 9.4 Hz, H-2’ or H-3’ or H-4’), 4.86 (1H, d, J = 9.4 Hz, H-1’), 4.30 (1H, dd, J = 12.4, 4.8 Hz, H-6’a), 4.16 (1H, dd, J = 12.5, <1 Hz, H-6’b), 3.92 (1H, ddd, J = 10.0, 4.6, 1.9 Hz, H-5’), 2.86 (2H, pseudo t, J = 5.8, 6.2 Hz, tetralin H-5’’), 2.40 (2H, pseudo t, J = 5.6, 6.2 Hz, tetralin H-8’’), 2.08, 2.07, 2.02, 1.93 (4 × 3H, 4 × s, CH3CO), 1.82–1.70 (4H, m, tetralin H-6’’, H-7’’). ESI-HRMS positive mode (m/z): calcd. for C26H31N3NaO9+ ([M + Na]+): 552.1953. Found: 552.1953.

1-Phenyl-4-(β- (5a). Triazole 2a (137 mg, 0.21 mmol) was dissolved in a 1:1 mixture of anhydr. EtOH and EtOAc (4 mL), Pd(C) (10 wt. %, 13 mg) was added and the mixture was stirred in H2 atmosphere (1 bar) at rt for 72 h. The catalyst was removed by filtration and the filtrate was purified by column chromatography (eluent: CHCl3-MeOH 7:3) to yield 58 mg (92%) colorless syrup. Rf = 0.46 (CHCl3-MeOH 7:3); [α]D = +15 (c 1.14, MeOH); 1H-NMR (D2O, 360 MHz) δ (ppm): 8.30 (1H, s, triazole H-5), 7.50–7.48 (2H, m, Ar), 7.40–7.36 (3H, m, Ar), 4.55 (1H, d, J = 9.7 Hz, H-1’), 3.91 (1H, dd, J = 12.1, <1 Hz, H-6’a), 3.78–3.71 (2H, m, H-2’ or H-3’ or H-4’, H-6’b), 3.64 (1H, pseudo t, J = 8.8, 8.2 Hz, H-2’ or H-3’ or H-4’), 3.58–3.55 (2H, m, H-2’ or H-3’ or H-4’, H-5’); 13C-NMR (D2O, 90 MHz) δ (ppm): 145.6 (triazole C-4), 136.0, 129.9, 129.6, 120.8 (Ar), 123.1 (triazole C-5), 80.3, 77.4, 73.7, 73.2, 69.8 (C-1’–C-5’), 61.1 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C14H17N3NaO5+ ([M + Na]+): 330.1060. Found: 330.1058.

1-(Naphthalen-2-yl)-4-(β- (5b). Prepared from compound 4b (72 mg, 0.14 mmol) according to General procedure 3. Yield: 47 mg (96%) white crystals. Rf = 0.35 (CHCl3-MeOH 8:2); Mp: 224–225 °C; [α]D = +12 (c 0.65, MeOH); 1H-NMR (DMSO-d6, 360 MHz) δ (ppm): 8.92 (1H, s, Ar), 8.45 (1H, s, triazole H-5), 8.17–8.01 (4H, m, Ar), 7.62 (2H, m, Ar), 4.36 (1H, d, J = 9.7 Hz, H-1’), 3.70 (1H, dd, J = 11.6, <1 Hz, H-6’a), 3.59 (1H, dd, J = 11.2, <1 Hz, H-6’b), 3.44 (1H, m, H-5’), 3.36–3.31 (2H, m, H-2’ and/or H-3’ and/or H-4’), 3.20 (1H, pseudo t, J = 9.0, 8.9 Hz; H-2’ or H-3’ or H-4’); 13C-NMR (DMSO-d6, 90 MHz) δ (ppm): 147.3 (triazole C-4), 134.3, 133.0, 132.4, 130.2, 128.4, 128.0, 127.7, 127.2, 122.3, 118.7, 117.8 (Ar), 81.4, 78.0, 74.3, 73.1, 70.3 (C-1’–C-5’), 61.3 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C18H19N3NaO5+ ([M + Na]+): 380.1217. Found: 380.1216.

1-(Naphthalen-1-yl)-4-(β- (5c). Prepared from compound 4c (79 mg, 0.15 mmol) according to General procedure 3. Yield: 51 mg (94%) pale brown syrup. Rf = 0.37 (CHCl3-MeOH 4:1); [α]D = +7 (c 0.42, MeOH); 1H-NMR (CD3OD, 360 MHz) δ (ppm): 8.37 (1H, s, triazole H-5), 8.10–8.08 (1H, m, Ar), 8.02–8.00 (1H, m, Ar), 7.62–7.54 (1H, m, Ar), 4.59 (1H, d, J = 9.7 Hz, H-1’), 3.93 (1H, dd, J = 11.8, <1 Hz, H-6’a), 3.77–3.72 (2H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’b), 3.62–3.50 (3H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’b); 13C-NMR (CD3OD, 90 MHz) δ (ppm): 147.6 (triazole C-4), 135.6, 134.8, 131.8, 129.8, 129.5, 129.0, 128.3, 126.2, 124.9, 123.2 (Ar), 127.5 (triazole C-5), 82.4, 79.6, 75.7, 75.1, 71.6 (C-1’–C-5’), 63.0 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C18H19N3NaO5+ ([M + Na]+): 380.1217. Found: 380.1216.

1-(2’,3’,4’,6’-Tetra-O-acetyl-β- (7). To a solution of 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl-bromide (6, 0.20 g, 0.49 mmol) and 4-phenylimidazole (0.14 g, 0.97 mmol) in anhydr. CH3CN (5 mL) mercury(II) cyanide (0.12 g, 0.49 mmol) and activated 4 Å molecular sieves (powder, 200 mg) were added. The reaction mixture was heated at 60 °C until the TLC (hexane-EtOAc 2:3) showed disappearance of 6. After cooling the reaction mixture to rt the insoluble inorganic salts and molecular sieves were filtered off, and the solution was evaporated under diminished pressure. The residue was dissolved in CHCl3 (30 mL) and extracted with 1M aq. KBr solution (2 × 20 mL) and water (20 mL), respectively. The organic layer was dried, filtered and evaporated. The residue was purified by column chromatography (hexane-EtOAc 2:3) to yield 140 mg (61%) white solid. Mp = 179–181 °C; Rf = 0.29 (hexane-EtOAc 1:2); [α]D = −54 (c 0.22, CHCl3); 1H-NMR (400 MHz, CDCl3) δ (ppm): 7.77 (2H, dd, J = 7.2, 1.3 Hz, Ph), 7.67 (1H, d, J = 1.1 Hz, imidazole CH), 7.40–7.36 (3H, m, Ph, imidazole CH), 7.26 (1H, dt, J = 7.2, 1.4 Hz, Ph), 5.42, 5.37 (2 × 1H, 2 pseudo t, J = 9.2, 9.1 Hz in each, H-2’, H-3’), 5.34 (1H, d, J = 9.1 Hz, H-1’), 5.26 (1H, pseudo t, J = 9.9, 9.1 Hz, H-4’), 4.30 (1H, dd, J = 12.6, 5.0 Hz, H-6’a), 4.15 (1H, dd, J = 12.6, 2.1 Hz, H-6’b), 3.95 (1H, ddd, J = 9.9, 5.0, 2.1 Hz, H-5’), 2.09, 2.07, 2.03, 1.88 (4 × 3H, 4 s, 4 × CH3CO); 13C-NMR (100 MHz, CDCl3) δ (ppm): 170.6, 170.1, 169.4, 168.8 (4 × CH3CO), 143.2 (imidazole C-4), 136.9 (imidazole C-2), 133.5, 128.7 (2), 127.3, 125.1 (2) (Ph), 112.3 (imidazole C-5), 83.8 (C-1’), 75.0 (C-5’), 73.0, 70.6 (C-2’, C-3’), 67.9 (C-4’), 61.8 (C-6’), 20.8, 20.6 (2), 20.3 (4 × CH3CO). ESI-HRMS positive mode (m/z): calcd. for C23H27N2O9+ ([M + H]+): 475.1711. Found: 475.1711.

1-(β- (8). Prepared from compound 7 (250 mg, 0.53 mmol) according to general procedure 3. Purification by recrystallisation from MeOH yielded 120 mg (75%) white solid. Rf = 0.45 (CHCl3-MeOH 7:3); Mp = 273–274 °C; [α]D = +56 (c 0.22, DMSO); 1H-NMR (360 MHz, DMSO-d6 + 1 drop of D2O) δ (ppm): 7.84 (1H, s, imidazole CH), 7.77–7.73 (3H, m, Ph, imidazole CH), 7.35 (2H, t, J = 7.4 Hz, Ph), 7.20 (1H, t, J = 7.4 Hz, Ph), 5.13 (1H, d, J = 9.1 Hz, H-1’), 3.67 (1H, H-6’a), 3.54 (1H, pseudo t, J = 9.8, 9.1 Hz, H-2’ or H-3’ or H-4’), 3.46 (1H, dd, J = 11.6, 5.6 Hz, H-6’b), 3.40–3.31 (2H, m, H-2’ or H-3’ or H-4’, H-5’), 3.23 (1H, pseudo t, J = 9.1, 9.1 Hz, H-2’ or H-3’ or H-4’); -13C-NMR (90 MHz, DMSO-d6) δ (ppm): 140.3 (imidazole C-4), 137.4 (imidazole C-2), 134.4, 128.3 (2), 126.1, 124.1 (2) (Ph), 114.1 (imidazole C-5), 85.4 (C-1’), 79.6, 77.0, 72.4, 69.6 (C-2’–C-5’), 60.8 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C15H21N2O5+ ([M + H]+): 307.1288. Found: 307.1286.

2-Phenyl-5-(2’,3’,4’,6’-tetra-O-benzoyl-β- (10a)

Method A: To the solution of tosylhydrazone 12 (100 mg, 0.13 mmol) in anhydr. pyridine benzenediazonium tetrafluoroborate (25 mg, 0.13 mmol) was added at −40 °C. The mixture was allowed to reach −10 °C in 20 min then CH2Cl2 was added and the mixture was washed with 10% aqueous HCl, saturated aqueous NaHCO3 and brine. The organic phase was dried, evaporated and the residue was purified by column chromatography (eluent: hexane-EtOAc 1:4 → 1:3 gradient) to give 57 mg (61%) yellowish syrup.

Method B: To the solution of tetrazole 9 (300 mg, 0.46 mmol) in anhydr. CH2Cl2 (6 mL) phenylboronic acid (1.6 equiv., 90 mg, 0.74 mmol), CuCl2 (0.12 equiv., 7 mg, 0.06 mmol), N,N,N’,N’-tetra-methylethylenediamine (0.12 equiv., 8 µL, 0.06 mmol) and K2CO3 (1.1 equiv., 70 mg, 0.51 mmol) were added and the mixture was stirred at r.t. under air. After 20 h CH2Cl2 was added and the solution was washed with 10% aqueous NH3, water and brine. The organic phase was dried, evaporated and the residue was purified by column chromatography (eluent: hexane-EtOAc 1:4 → 1:3 gradient) to give 319 mg (95%) colorless syrup.

Rf = 0.43 (hexane-EtOAc 3:2); [α]D = −5 (c 0.36, CHCl3); 1H-NMR (CDCl3, 400 MHz) δ (ppm): 8.03–7.80 (10H, m, Ar), 7.53–7.27 (15H, m, Ar), 6.23 (1H, pseudo t, J = 9.7, 9.8 Hz, H-2’ or H-3’ or H-4’), 6.09 (1H, pseudo t, J = 9.5, 9.5 Hz, H-2’ or H-3’ or H-4’), 5.90 (1H, pseudo t, J = 9.7, 9.8 Hz, H-2’ or H-3’ or H-4’), 5.38 (1H, d, J = 10.0 Hz, H-1’), 4.69 (1H, dd, J = 12.4, 2.9 Hz, H-6’a), 4.56 (1H, dd, J = 12.4, 5.1 Hz, H-6’b), 4.42 (1H, ddd, J = 9.9, 5.1, 2.9 Hz, H-5’); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 166.1, 165.8, 165.1, 164.6 (PhCO), 162.2 (tetrazole C-5), 136.6 (phenyl C-1”), 133.4-128.2 (Ar), 120.0 (phenyl C-2”), 77.0, 74.3, 72.5, 71.1, 69.4 (C-1’–C-5’), 63.2 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C41H32N4NaO9 + ([M + Na]+): 747.2061. Found: 747.2060.

2-Methyl-5-(2’,3’,4’,6’-tetra-O-benzoyl-β- (10e) and 1-methyl-5-(2’,3’,4’,6’-tetra-O-benzoyl-β- (11e). A solution of diazomethane was prepared by a portionwise addition of N-nitroso-N-methylurea (400 mg, 3.88 mmol) to a stirred mixture of diethyl ether (5 mL) and 40% w/w aqueous solution of KOH (5 mL) at 0 °C. Ethereal phase was added dropwise to the solution of tetrazole 9 (500 mg, 0.77 mmol) in anhydr. CH2Cl2 (22 mL) at r.t. After disappearance of the tetrazole (TLC, PhMe-EtOAc 4:1) the solvent was removed in vacuo, and the residue was purified by column chromatography (eluent: PhMe-EtOAc 20:1 → 10:1 gradient) to give 10e (192 mg, 38%) and 11e (194 mg, 38%).

10e: white amorphous solid. Rf = 0.46 (PhMe-EtOAc 4:1); [α]D = +36 (c 0.45, CHCl3); 1H-NMR (CDCl3, 400 MHz) δ (ppm): 8.01–7.79 (8H, m, Ar), 7.50–7.21 (12H, m, Ar), 6.17–6.08 (2H, m, H-2’, H-3’), 5.90 (1H, pseudo t, J = 9.5, 9.4 Hz, H-4’), 5.35 (1H, d, J = 9.3 Hz, H-1’), 4.68 (1H, dd, J = 12.4, 2.9 Hz, H-6’a), 4.56 (1H, dd, J = 12.4, 5.1 Hz, H-6’b), 4.42 (1H, ddd, J = 9.6, 5.0, 2.8 Hz, H-5’), 4.19 (3H, s, CH3); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 166.0, 165.7, 165.0, 164.4 (PhCO), 162.1 (tetrazole C-5), 133.3–128.2 (Ar), 76.8, 74.2, 72.4, 71.1, 69.3 (C-1’–C-5’), 63.1 (C-6’), 39.4 (CH3). ESI-HRMS positive mode (m/z): calcd. for C36H30N4NaO9+ ([M + Na]+): 685.1905. Found: 685.1900.

11e: white amorphous solid. Rf = 0.34 (PhMe-EtOAc 4:1); [α]D = −7 (c 0.53, CHCl3); 1H-NMR (CDCl3, 400 MHz) δ (ppm): 8.05–7.77 (8H, m, Ar), 7.58–7.23 (12H, m, Ar), 6.19 (1H, pseudo t, J = 9.6, 9.6 Hz, H-3’), 5.90 (1H, pseudo t, J = 9.8, 9.9 Hz, H-4’), 5.83 (1H, pseudo t, J = 9.9, 9.9 Hz, H-2’), 5.49 (1H, d, J = 10.2 Hz, H-1’), 4.74 (1H, dd, J = 12.5, 2.6 Hz, H-6’a), 4.54 (1H, dd, J = 12.5, 4.9 Hz, H-6’b), 4.42 (1H, ddd, J = 9.3, 4.7, 2.6 Hz, H-5’), 4.24 (3H, s, CH3); 13C-NMR (CDCl3, 90 MHz) δ (ppm): 165.8, 165.5, 165.1 (2) (PhCO), 149.9 (tetrazole C-5), 133.6–127.9 (Ar), 77.2, 73.1, 71.8, 69.8, 68.8 (C-1’–C-5’), 62.3 (C-6’), 34.7 (CH3). ESI-HRMS positive mode (m/z): calcd. for C36H30N4NaO9+ ([M + Na]+): 685.1905. Found: 685.1902.

2-Phenyl-5-(β- (13a). Prepared from compound 10a (200 mg, 0.28 mmol) according to general procedure 3. Yield: 80 mg (94%) white amorphous solid. Rf = 0.41 (CHCl3-MeOH 4:1); [α]D = +12 (c 0.27, MeOH); 1H-NMR (DMSO-d6, 360 MHz) δ (ppm): 8.10–8.07 (2H, m, Ar), 7.70–7.59 (3H, m, Ar), 4.58 (1H, d, J = 9.8 Hz, H-1’), 3.77–3.69 (2H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’), 3.48–3.34 (3H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’), 3.23 (1H, pseudo t, J = 9.1, 9.0 Hz, H-2’ or H-3’ or H-4’); 13C-NMR (DMSO-d6, 90 MHz) δ (ppm): 164.8 (tetrazole C-5), 136.2, 130.3, 130.2, 119.9 (Ar), 81.7, 77.6, 73.4, 72.5, 70.1 (C-1’–C-5’), 61.1 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C13H16N4NaO5+ ([M + Na]+): 331.1013. Found: 331.1013.

2-Methyl-5-(β- (13e). Prepared from compound 10e (150 mg, 0.23 mmol) according to general procedure 3. Yield: 40 mg (72%) colourless syrup. Rf = 0.41 (CHCl3-MeOH 7:3); [α]D = +1 (c 0.63, MeOH); 1H-NMR (D2O, 400 MHz) δ (ppm): 4.76 (1H, d, J = 10.0 Hz, H-1’), 4.41 (3H, s, CH3), 3.92 (1H, dd, J = 12.4, 1.8 Hz, H-6’a), 3.81 (1H, pseudo t, J = 9.3, 9.7 Hz, H-2’ or H-3’ or H-4’), 3.75 (1H, dd, J = 12.4, 5.7 Hz, H-6’b), 3.68-3.58 (2H, m, H-2’ or H-3’ or H-4’, H-5’), 3.56 (1H, pseudo t, J = 9.2, 9.4 Hz, H-2’ or H-3’ or H-4’); 13C-NMR (D2O, 100 MHz) δ (ppm): 163.9 (tetrazole C-5), 81.0, 77.5, 73.6, 73.1, 70.1 (C-1’–C-5’), 61.4 (C-6’), 40.4 (CH3). ESI-HRMS positive mode (m/z): calcd. for C8H14N4NaO5+ ([M + Na]+): 269.0856. Found: 269.0855.

1-Methyl-5-(β- (14e). Prepared from compound 11e (150 mg, 0.23 mmol) according to general procedure 3. Yield: 54 mg (97%) pale yellow syrup. Rf = 0.33 (CHCl3-MeOH 7:3); [α]D = +7 (c 0.83, MeOH); 1H-NMR (D2O, 360 MHz) δ (ppm): 4.91 (1H, d, J = 9.7 Hz, H-1’), 4.17 (3H, s, CH3), 3.92 (1H, dd, J = 12.4, <1 Hz, H-6’a), 3.83–3.66 (4H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’b), 3.57 (1H, pseudo t, J = 9.4, 9.1 Hz, H-2’ or H-3’ or H-4’); 13C-NMR (D2O, 90 MHz) δ (ppm): 153.9 (tetrazole C-5), 81.1, 77.3, 73.0, 71.5, 69.9 (C-1’–C-5’), 61.4 (C-6’), 35.1 (CH3). ESI-HRMS positive mode (m/z): calcd. for C8H14N4NaO5+ ([M + Na]+): 269.0856. Found: 269.0857.

5-Phenyl-2-(2’,3’,4’,6’-tetra-O-acetyl-β- (15a) and 5-phenyl-1-(2’,3’,4’,6’-tetra-O-acetyl-β- (16a). Prepared according to general procedure 4 from bromide 6 (500 mg, 1.22 mmol) and 5-phenyltetrazole (355 mg, 2.43 mmol). Products were separated by column chromatography (eluent: hexane-acetone 3:1) to give 15a (460 mg, 79%) and 16a (96 mg, 17%). 1H and 13C-NMR spectra of the isolated compounds are in agreement with those reported earlier [61].

5-Methyl-2-(2,3,4,6-tetra-O-acetyl-β-15e). Prepared according to general procedure 4 from n class="Chemical">bromide 6 (500 mg, 1.22 mmol) and 5-methyltetrazole (204 mg, 2.43 mmol). Products were separated by column chromatography (eluent: hexane-acetone 9:1 → 4:1 gradient) to give 15e (131 mg, 26%) and glycal 17 [67] (181 mg, 45%).

15e: White amorphous solid. Rf = 0.48 (hexane-acetone 1:1); [α]D = +7 (c 0.46, CHCl3); 1H-NMR (CDCl3, 400 MHz) δ (ppm): 6.06 (1H, d, J = 9.4 Hz, H-1’), 5.83 (1H, pseudo t, J = 9.4, 9.4 Hz, H-2’ or H-3’ or H-4’), 5.42 (1H, pseudo t, J = 9.5, 9.5 Hz, H-2’ or H-3’ or H-4’), 5.30 (1H, pseudo t, J = 9.9, 9.7 Hz, H-2’ or H-3’ or H-4’), 4.30 (1H, dd, J = 12.7, 5.0 Hz, H-6’a), 4.17 (1H, dd, J = 12.7, 2.0 Hz, H-6’b), 4.03 (1H, ddd, J = 10.0, 5.0, 2.0 Hz, H-5’), 2.58 (3H, s, CH3), 2.08, 2.08, 2.04, 1.85 (4 × 3H, s, 4 × CH3CO); 13C-NMR (CDCl3, 100 MHz) δ (ppm): 170.6, 170.2, 169.2, 168.4 (CH3CO), 163.9 (tetrazole C-5), 86.5 (C-1’), 75.1, 73.0, 69.8, 67.4 (C-2’–C-5’), 61.5 (C-6’), 20.7, 20.6 (2), 20.2 (CH3CO), 11.1 (CH3). ESI-HRMS positive mode (m/z): calcd. for C16H22N4NaO9+ ([M + Na]+): 437.1279. Found: 437.1281.

5-Phenyl-2-(β- (18a). Prepared from compound 15a (155 mg, 0.33 mmol) according to General procedure 3. Yield: 85 mg (85%) white amorphous solid. Rf = 0.29 (CHCl3-MeOH 4:1); [α]D = −4 (c 1.31, MeOH); 1H-NMR (D2O, 400 MHz) δ (ppm): 8.01-7.98 (2H, m, Ar), 7.54–7.50 (3H, m, Ar), 6.08 (1H, d, J = 9.2 Hz, H-1’), 4.20 (1H, pseudo t, J = 9.3, 9.3 Hz, H-2’ or H-3’ or H-4’), 3.97–3.93 (1H, m, H-2’ or H-3’ or H-4’ or H-5’ or H-6’), 3.82–3.76 (3H, m, H-2’ and/or H-3’ and/or H-4’ and/or H-5’ and/or H-6’), 3.67 (1H, pseudo t, J = 9.2, 9.2 Hz, H-2’ or H-3’ or H-4’); 13C-NMR (D2O, 100 MHz) δ (ppm): 165.9 (tetrazole C-5), 131.9, 129.9, 127.5, 126.3 (Ar), 89.9 (C-1’), 79.7, 76.4, 72.5, 69.5 (C-2’–C-5’), 61.1 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C13H16N4NaO5+ ([M + Na]+): 331.1013. Found: 331.1014.

5-Methyl-2-(β- (18e). Prepared from compound 15e (136 mg, 0.33 mmol) according to general procedure 3. Yield: 68 mg (84%) white amorphous solid. Rf = 0.29 (CHCl3-MeOH 4:1); [α]D = −14 (c 0.66, CHCl3); 1H-NMR (D2O, 400 MHz) δ (ppm): 6.03 (1H, d, J = 9.2 Hz, H-1’), 4.13 (1H, pseudo t, J = 9.2, 9.3 Hz, H-2’ or H-3’ or H-4’), 3.93 (1H, dd, J = 10.7, <1 Hz, H-6’a), 3.82–3.73 (2H, m, H-5’ and H-6’b), 3.75 (1H, pseudo t, J = 9.2, 9.3 Hz, H-2’ or H-3’ or H-4’), 3.64 (1H, pseudo t, J = 9.3, 9.3 Hz, H-2’ or H-3’ or H-4’), 2.58 (3H, s, CH3); 13C-NMR (D2O, 100 MHz) δ (ppm): 164.7 (tetrazole C-5), 89.5 (C-1’), 79.6, 76.4, 72.4, 69.5 (C-2’–C-5’), 61.0 (C-6’), 10.5 (CH3). ESI-HRMS positive mode (m/z): calcd. for C8H14N4NaO5+ ([M + Na]+): 269.0856. Found: 269.0858.

5-Phenyl-1-(β- (19a). Prepared from compound 16a (86 mg, 0.18 mmol) according to general procedure 3. Yield: 48 mg (86%) colourless syrup. Rf = 0.29 (CHCl3-MeOH 4:1); [α]D = +17 (c 0.68, MeOH); 1H-NMR (D2O, 400 MHz) δ (ppm): 7.74–7.67 (3H, m, Ar), 7.64–7.60 (2H, m, Ar), 5.60 (1H, d, J = 9.1 Hz, H-1’), 4.31 (1H, pseudo t, J = 9.1, 9.1 Hz, H-2’ or H-3’ or H-4’), 3.95 (1H, dd, J = 12.4, 1.7 Hz, H-6’a), 3.78 (1H, dd, J = 12.4, .6 Hz, H-6’b), 3.71, (1H, ddd, J = 9.4, 5.8, 1.4 Hz, H-5’), 3.66–3.62 (2H, m, H-2’ and/or H-3’ and/or H-4’); 13C-NMR (D2O, 100 MHz) δ (ppm): 157.3 (tetrazole C-5), 133.0, 130.1, 129.8, 122.3 (Ar), 85.5, 79.5, 76.5, 72.0, 69.6 (C-1’–C-5’), 61.1 (C-6’). ESI-HRMS positive mode (m/z): calcd. for C13H16N4NaO5+ ([M + Na]+): 331.1013. Found: 331.1012.

4. Conclusions

In this study, initiated by the objective of extending the structure-activity relationships of C- and N-β-d-glucopyranosyl derivatives of a wide range of azole type heterocycles as glycogen phosphorylase inhibitors, new methyl and aryl substituted 1,2,3-triazoles, imidazoles and tetrazoles have been synthesized. Enzyme kinetic investigation of the new compounds showed most of them to have no significant inhibitory activity against RMGPb. These and previous [44] experiences with β-d-Glc-azole-Ar type compounds indicate that the inhibitory effect of these is highly sensible to the structure of the azole moieties and the range of efficacy expands from inactives to the best known glucose derived inhibitors. The understanding of such an enormous variability seems to be beyond simple or intuitive discretion, therefore, computational studies are underway to get a deeper insight in these phenomena.