4,5,6-Tri-O-acetyl-2,3-di-S-ethyl-2,3-dithio-d-allose diethyl dithio-acetal.

The title compound, C(20)H(36)O(6)S(4), was obtained by ethanethiol-ysis of 3,5,6-tri-O-acetyl-1,2-O-isopropyl-idene-α-d-gluco-furan--ose. One of the ethyl groups is disordered over two sites with refined occupancies of 0.869 (6) and 0.131 (6). Compared with the precursor, the absolute configuration of the stereocenters at positions C-3 and C-2 are inverted and maintained, respectively.

Related literature

For the bioactiviy of nucleosides, see: Zhang et al. (2007 ▶); Merino et al. (2008 ▶). For the structure of the precursor, 3,5,6-tri-O-acetyl-1,2-O-isopropyl­idene-α-d-glucofuran­ose, see: Wu et al. (2009 ▶). For related structures, see: Bethel & Ferrier (1972 ▶); Berrang & Hortor (1970 ▶); Divjaković et al. (1992 ▶).

Experimental

Crystal data

C20H36O6S4

M = 500.73

Monoclinic,

a = 8.3395 (12) Å

b = 16.726 (2) Å

c = 9.2027 (14) Å

β = 95.772 (5)°

V = 1277.2 (3) Å3

Z = 2

Mo Kα radiation

μ = 0.40 mm−1

T = 113 K

0.26 × 0.20 × 0.18 mm

Data collection

Rigaku Saturn diffractometer

Absorption correction: multi-scan (CrystalClear; Rigaku/MSC, 2005 ▶) T min = 0.902, T max = 0.931

16052 measured reflections

6060 independent reflections

5802 reflections with I > 2σ(I)

R int = 0.032

Refinement

R[F 2 > 2σ(F 2)] = 0.032

wR(F 2) = 0.066

S = 1.04

6060 reflections

298 parameters

23 restraints

H-atom parameters constrained

Δρmax = 0.20 e Å−3

Δρmin = −0.29 e Å−3

Absolute structure: Flack (1983 ▶), 2919 Friedel pairs

Flack parameter: −0.03 (4)

Data collection: CrystalClear (Rigaku/MSC, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809015694/lh2804sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809015694/lh2804Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C20H36O6S4	F(000) = 536
Mr = 500.73	Dx = 1.302 Mg m−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71070 Å
Hall symbol: P 2yb	Cell parameters from 4760 reflections
a = 8.3395 (12) Å	θ = 2.2–27.9°
b = 16.726 (2) Å	µ = 0.40 mm−1
c = 9.2027 (14) Å	T = 113 K
β = 95.772 (5)°	Block, colorless
V = 1277.2 (3) Å3	0.26 × 0.20 × 0.18 mm
Z = 2

Rigaku Saturn diffractometer	6060 independent reflections
Radiation source: rotating anode	5802 reflections with I > 2σ(I)
confocal	Rint = 0.032
Detector resolution: 14.63 pixels mm-1	θmax = 27.9°, θmin = 2.2°
ω scans	h = −10→10
Absorption correction: multi-scan (CrystalClear; Rigaku/MSC, 2005)	k = −21→22
Tmin = 0.902, Tmax = 0.931	l = −12→12
16052 measured reflections

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.032	H-atom parameters constrained
wR(F2) = 0.066	w = 1/[σ2(Fo2) + (0.0326P)2] where P = (Fo2 + 2Fc2)/3
S = 1.04	(Δ/σ)max = 0.001
6060 reflections	Δρmax = 0.20 e Å−3
298 parameters	Δρmin = −0.29 e Å−3
23 restraints	Absolute structure: Flack (1983), 2919 Friedel pairs
Primary atom site location: structure-invariant direct methods	Flack parameter: −0.03 (4)

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	0.74081 (5)	−0.08494 (3)	0.79166 (5)	0.02103 (10)
S2	0.70511 (5)	0.08746 (3)	0.88989 (5)	0.02203 (10)
S3	0.41930 (5)	0.00547 (3)	0.66199 (5)	0.01940 (10)
S4	0.85901 (5)	0.02564 (3)	0.42590 (5)	0.02148 (10)
O1	0.56270 (15)	−0.06561 (7)	0.23706 (13)	0.0182 (3)
O2	0.32000 (18)	−0.12020 (10)	0.25917 (18)	0.0405 (4)
O3	0.54225 (14)	0.14186 (7)	0.33931 (12)	0.0169 (3)
O4	0.68402 (15)	0.21225 (8)	0.18563 (14)	0.0269 (3)
O5	0.25647 (13)	0.10093 (8)	0.19236 (13)	0.0209 (3)
O6	0.26208 (18)	0.22570 (8)	0.10243 (18)	0.0378 (4)
C1	0.74322 (19)	0.02080 (11)	0.74033 (17)	0.0171 (3)
H1	0.8521	0.0336	0.7099	0.021*
C2	0.61765 (18)	0.03465 (11)	0.60845 (18)	0.0156 (3)
H2	0.6143	0.0933	0.5873	0.019*
C3	0.66042 (18)	−0.00888 (10)	0.46908 (17)	0.0147 (3)
H3	0.6708	−0.0670	0.4933	0.018*
C4	0.53286 (19)	−0.00125 (11)	0.33657 (17)	0.0148 (3)
H4	0.4224	−0.0068	0.3689	0.018*
C5	0.5413 (2)	0.07353 (10)	0.24304 (18)	0.0164 (4)
H5	0.6440	0.0727	0.1957	0.020*
C6	0.3999 (2)	0.08169 (12)	0.12490 (18)	0.0202 (4)
H6A	0.4227	0.1244	0.0554	0.024*
H6B	0.3843	0.0309	0.0700	0.024*
C7	0.8968 (2)	−0.08772 (14)	0.94224 (19)	0.0284 (4)
H7A	0.8763	−0.0444	1.0112	0.034*
H7B	0.8888	−0.1391	0.9944	0.034*
C8	1.0684 (2)	−0.07889 (15)	0.9010 (3)	0.0398 (5)
H8A	1.0926	−0.1230	0.8366	0.060*
H8B	1.1441	−0.0801	0.9896	0.060*
H8C	1.0788	−0.0279	0.8503	0.060*
C9	0.8906 (2)	0.14400 (14)	0.9124 (2)	0.0311 (5)
H9A	0.8924	0.1759	1.0031	0.037*
H9B	0.9821	0.1061	0.9247	0.037*
C10	0.9154 (3)	0.19954 (14)	0.7876 (3)	0.0395 (5)
H10A	0.9222	0.1683	0.6984	0.059*
H10B	1.0155	0.2297	0.8104	0.059*
H10C	0.8245	0.2368	0.7729	0.059*
C11	0.2932 (2)	0.08823 (13)	0.59307 (19)	0.0237 (4)
H11A	0.3106	0.0975	0.4896	0.028*
H11B	0.1789	0.0730	0.5962	0.028*
C12	0.3242 (2)	0.16570 (13)	0.6765 (2)	0.0302 (5)
H12A	0.2985	0.1585	0.7773	0.045*
H12B	0.2561	0.2080	0.6296	0.045*
H12C	0.4378	0.1806	0.6766	0.045*
C13	0.9482 (3)	−0.06248 (16)	0.3541 (3)	0.0317 (8)	0.869 (6)
H13A	0.8677	−0.0883	0.2826	0.038*	0.869 (6)
H13B	1.0406	−0.0461	0.3013	0.038*	0.869 (6)
C14	1.0059 (4)	−0.1230 (2)	0.4699 (3)	0.0428 (9)	0.869 (6)
H14A	1.0905	−0.0991	0.5378	0.064*	0.869 (6)
H14B	1.0490	−0.1700	0.4233	0.064*	0.869 (6)
H14C	0.9154	−0.1392	0.5235	0.064*	0.869 (6)
C13'	0.9867 (15)	−0.0625 (8)	0.4615 (17)	0.024 (5)	0.131 (6)
H13C	1.0967	−0.0488	0.4379	0.029*	0.131 (6)
H13D	0.9937	−0.0741	0.5674	0.029*	0.131 (6)
C14'	0.935 (2)	−0.1377 (8)	0.381 (2)	0.036 (4)	0.131 (6)
H14D	0.8573	−0.1665	0.4339	0.054*	0.131 (6)
H14E	1.0297	−0.1717	0.3722	0.054*	0.131 (6)
H14F	0.8855	−0.1240	0.2827	0.054*	0.131 (6)
C15	0.4443 (2)	−0.12014 (11)	0.20382 (19)	0.0200 (4)
C16	0.4899 (3)	−0.17588 (12)	0.0885 (2)	0.0277 (4)
H16A	0.4155	−0.2214	0.0805	0.042*
H16B	0.6000	−0.1952	0.1143	0.042*
H16C	0.4843	−0.1477	−0.0053	0.042*
C17	0.6157 (2)	0.20907 (11)	0.2941 (2)	0.0209 (4)
C18	0.5959 (3)	0.27634 (12)	0.3979 (2)	0.0326 (5)
H18A	0.6485	0.3244	0.3644	0.049*
H18B	0.6454	0.2617	0.4954	0.049*
H18C	0.4810	0.2871	0.4021	0.049*
C19	0.2065 (2)	0.17773 (11)	0.1783 (2)	0.0221 (4)
C20	0.0766 (2)	0.19526 (13)	0.2743 (2)	0.0301 (5)
H20A	0.1246	0.2033	0.3748	0.045*
H20B	0.0012	0.1502	0.2712	0.045*
H20C	0.0187	0.2437	0.2397	0.045*

	U11	U22	U33	U12	U13	U23
S1	0.0232 (2)	0.0209 (2)	0.0183 (2)	−0.00083 (19)	−0.00179 (18)	0.00364 (18)
S2	0.0236 (2)	0.0275 (2)	0.0155 (2)	−0.00207 (19)	0.00384 (17)	−0.00323 (19)
S3	0.0155 (2)	0.0251 (2)	0.0183 (2)	−0.00173 (18)	0.00489 (16)	0.00091 (18)
S4	0.01363 (19)	0.0294 (3)	0.0218 (2)	−0.00129 (18)	0.00362 (16)	0.00257 (19)
O1	0.0183 (6)	0.0201 (7)	0.0166 (6)	−0.0007 (5)	0.0034 (5)	−0.0072 (5)
O2	0.0312 (8)	0.0411 (9)	0.0523 (10)	−0.0176 (7)	0.0194 (7)	−0.0234 (8)
O3	0.0213 (6)	0.0138 (6)	0.0157 (6)	−0.0013 (5)	0.0026 (5)	0.0002 (5)
O4	0.0221 (7)	0.0292 (8)	0.0298 (7)	−0.0023 (6)	0.0050 (6)	0.0102 (6)
O5	0.0175 (6)	0.0194 (7)	0.0253 (7)	0.0012 (5)	−0.0005 (5)	0.0021 (5)
O6	0.0368 (8)	0.0244 (8)	0.0556 (10)	0.0038 (6)	0.0209 (8)	0.0118 (7)
C1	0.0174 (8)	0.0212 (9)	0.0128 (8)	−0.0003 (7)	0.0018 (6)	−0.0010 (7)
C2	0.0128 (8)	0.0171 (8)	0.0167 (8)	−0.0016 (7)	0.0006 (6)	−0.0001 (6)
C3	0.0146 (8)	0.0165 (9)	0.0133 (8)	0.0000 (7)	0.0028 (6)	0.0000 (7)
C4	0.0153 (8)	0.0159 (8)	0.0132 (8)	0.0026 (7)	0.0009 (6)	−0.0056 (7)
C5	0.0152 (8)	0.0166 (9)	0.0172 (9)	0.0016 (7)	0.0016 (6)	−0.0023 (7)
C6	0.0209 (9)	0.0257 (10)	0.0138 (8)	0.0023 (8)	0.0011 (7)	−0.0024 (7)
C7	0.0352 (10)	0.0305 (11)	0.0176 (9)	0.0017 (9)	−0.0064 (8)	0.0041 (9)
C8	0.0276 (11)	0.0400 (13)	0.0482 (14)	0.0029 (10)	−0.0139 (9)	0.0012 (11)
C9	0.0263 (10)	0.0344 (12)	0.0317 (11)	−0.0028 (9)	−0.0008 (8)	−0.0138 (9)
C10	0.0338 (11)	0.0283 (12)	0.0586 (15)	−0.0064 (10)	0.0160 (11)	−0.0079 (11)
C11	0.0174 (8)	0.0356 (11)	0.0182 (9)	0.0039 (8)	0.0029 (7)	0.0010 (9)
C12	0.0293 (11)	0.0346 (12)	0.0271 (11)	0.0066 (9)	0.0041 (8)	−0.0036 (9)
C13	0.0213 (12)	0.0515 (18)	0.0234 (15)	0.0072 (11)	0.0073 (10)	−0.0077 (11)
C14	0.0442 (17)	0.046 (2)	0.0393 (18)	0.0195 (14)	0.0118 (13)	−0.0025 (14)
C13'	0.007 (7)	0.045 (12)	0.022 (10)	−0.005 (6)	0.004 (6)	0.002 (7)
C14'	0.032 (7)	0.024 (7)	0.050 (8)	0.010 (6)	−0.009 (6)	−0.005 (6)
C15	0.0265 (10)	0.0197 (9)	0.0138 (9)	−0.0023 (8)	0.0025 (7)	−0.0008 (7)
C16	0.0377 (11)	0.0240 (10)	0.0222 (10)	−0.0048 (9)	0.0067 (8)	−0.0076 (8)
C17	0.0155 (8)	0.0178 (9)	0.0281 (10)	0.0003 (7)	−0.0037 (7)	0.0074 (8)
C18	0.0386 (12)	0.0200 (10)	0.0382 (13)	−0.0062 (9)	−0.0003 (10)	−0.0018 (8)
C19	0.0166 (8)	0.0230 (10)	0.0253 (10)	0.0003 (8)	−0.0043 (7)	0.0008 (8)
C20	0.0242 (10)	0.0332 (12)	0.0329 (12)	0.0057 (9)	0.0033 (8)	0.0084 (9)

S1—C7	1.8035 (18)	C9—C10	1.507 (3)
S1—C1	1.8313 (19)	C9—H9A	0.9900
S2—C9	1.807 (2)	C9—H9B	0.9900
S2—C1	1.8238 (17)	C10—H10A	0.9800
S3—C11	1.814 (2)	C10—H10B	0.9800
S3—C2	1.8387 (16)	C10—H10C	0.9800
S4—C13	1.806 (2)	C11—C12	1.515 (3)
S4—C13'	1.829 (13)	C11—H11A	0.9900
S4—C3	1.8348 (16)	C11—H11B	0.9900
O1—C15	1.357 (2)	C12—H12A	0.9800
O1—C4	1.4510 (19)	C12—H12B	0.9800
O2—C15	1.200 (2)	C12—H12C	0.9800
O3—C17	1.365 (2)	C13—C14	1.513 (4)
O3—C5	1.446 (2)	C13—H13A	0.9900
O4—C17	1.199 (2)	C13—H13B	0.9900
O5—C19	1.352 (2)	C14—H14A	0.9800
O5—C6	1.439 (2)	C14—H14B	0.9800
O6—C19	1.188 (2)	C14—H14C	0.9800
C1—C2	1.539 (2)	C13'—C14'	1.502 (19)
C1—H1	1.0000	C13'—H13C	0.9900
C2—C3	1.547 (2)	C13'—H13D	0.9900
C2—H2	1.0000	C14'—H14D	0.9800
C3—C4	1.541 (2)	C14'—H14E	0.9800
C3—H3	1.0000	C14'—H14F	0.9800
C4—C5	1.524 (2)	C15—C16	1.491 (2)
C4—H4	1.0000	C16—H16A	0.9800
C5—C6	1.527 (2)	C16—H16B	0.9800
C5—H5	1.0000	C16—H16C	0.9800
C6—H6A	0.9900	C17—C18	1.496 (3)
C6—H6B	0.9900	C18—H18A	0.9800
C7—C8	1.524 (3)	C18—H18B	0.9800
C7—H7A	0.9900	C18—H18C	0.9800
C7—H7B	0.9900	C19—C20	1.495 (3)
C8—H8A	0.9800	C20—H20A	0.9800
C8—H8B	0.9800	C20—H20B	0.9800
C8—H8C	0.9800	C20—H20C	0.9800
C7—S1—C1	101.38 (9)	C9—C10—H10A	109.5
C9—S2—C1	101.20 (9)	C9—C10—H10B	109.5
C11—S3—C2	102.08 (8)	H10A—C10—H10B	109.5
C13—S4—C13'	32.2 (5)	C9—C10—H10C	109.5
C13—S4—C3	103.66 (10)	H10A—C10—H10C	109.5
C13'—S4—C3	103.3 (4)	H10B—C10—H10C	109.5
C15—O1—C4	118.30 (13)	C12—C11—S3	114.35 (13)
C17—O3—C5	116.06 (13)	C12—C11—H11A	108.7
C19—O5—C6	115.63 (14)	S3—C11—H11A	108.7
C2—C1—S2	110.29 (11)	C12—C11—H11B	108.7
C2—C1—S1	108.94 (11)	S3—C11—H11B	108.7
S2—C1—S1	112.86 (9)	H11A—C11—H11B	107.6
C2—C1—H1	108.2	C11—C12—H12A	109.5
S2—C1—H1	108.2	C11—C12—H12B	109.5
S1—C1—H1	108.2	H12A—C12—H12B	109.5
C1—C2—C3	112.81 (13)	C11—C12—H12C	109.5
C1—C2—S3	107.93 (11)	H12A—C12—H12C	109.5
C3—C2—S3	112.69 (11)	H12B—C12—H12C	109.5
C1—C2—H2	107.7	C14—C13—S4	113.70 (19)
C3—C2—H2	107.7	C14—C13—H13A	108.8
S3—C2—H2	107.7	S4—C13—H13A	108.8
C4—C3—C2	114.75 (13)	C14—C13—H13B	108.8
C4—C3—S4	111.65 (11)	S4—C13—H13B	108.8
C2—C3—S4	108.65 (11)	H13A—C13—H13B	107.7
C4—C3—H3	107.1	C14'—C13'—S4	117.0 (11)
C2—C3—H3	107.1	C14'—C13'—H13C	108.0
S4—C3—H3	107.1	S4—C13'—H13C	108.0
O1—C4—C5	103.41 (12)	C14'—C13'—H13D	108.0
O1—C4—C3	106.83 (13)	S4—C13'—H13D	108.0
C5—C4—C3	116.60 (14)	H13C—C13'—H13D	107.3
O1—C4—H4	109.9	C13'—C14'—H14D	109.5
C5—C4—H4	109.9	C13'—C14'—H14E	109.5
C3—C4—H4	109.9	H14D—C14'—H14E	109.5
O3—C5—C4	107.49 (13)	C13'—C14'—H14F	109.5
O3—C5—C6	108.79 (13)	H14D—C14'—H14F	109.5
C4—C5—C6	113.55 (14)	H14E—C14'—H14F	109.5
O3—C5—H5	109.0	O2—C15—O1	123.03 (17)
C4—C5—H5	109.0	O2—C15—C16	126.52 (18)
C6—C5—H5	109.0	O1—C15—C16	110.42 (15)
O5—C6—C5	109.18 (13)	C15—C16—H16A	109.5
O5—C6—H6A	109.8	C15—C16—H16B	109.5
C5—C6—H6A	109.8	H16A—C16—H16B	109.5
O5—C6—H6B	109.8	C15—C16—H16C	109.5
C5—C6—H6B	109.8	H16A—C16—H16C	109.5
H6A—C6—H6B	108.3	H16B—C16—H16C	109.5
C8—C7—S1	115.40 (14)	O4—C17—O3	123.77 (18)
C8—C7—H7A	108.4	O4—C17—C18	126.18 (18)
S1—C7—H7A	108.4	O3—C17—C18	110.05 (15)
C8—C7—H7B	108.4	C17—C18—H18A	109.5
S1—C7—H7B	108.4	C17—C18—H18B	109.5
H7A—C7—H7B	107.5	H18A—C18—H18B	109.5
C7—C8—H8A	109.5	C17—C18—H18C	109.5
C7—C8—H8B	109.5	H18A—C18—H18C	109.5
H8A—C8—H8B	109.5	H18B—C18—H18C	109.5
C7—C8—H8C	109.5	O6—C19—O5	124.29 (17)
H8A—C8—H8C	109.5	O6—C19—C20	124.31 (18)
H8B—C8—H8C	109.5	O5—C19—C20	111.37 (16)
C10—C9—S2	114.64 (15)	C19—C20—H20A	109.5
C10—C9—H9A	108.6	C19—C20—H20B	109.5
S2—C9—H9A	108.6	H20A—C20—H20B	109.5
C10—C9—H9B	108.6	C19—C20—H20C	109.5
S2—C9—H9B	108.6	H20A—C20—H20C	109.5
H9A—C9—H9B	107.6	H20B—C20—H20C	109.5
C9—S2—C1—C2	−119.35 (13)	S4—C3—C4—C5	−39.69 (17)
C9—S2—C1—S1	118.55 (11)	C17—O3—C5—C4	153.04 (14)
C7—S1—C1—C2	178.77 (11)	C17—O3—C5—C6	−83.62 (17)
C7—S1—C1—S2	−58.37 (11)	O1—C4—C5—O3	−169.73 (12)
S2—C1—C2—C3	169.79 (11)	C3—C4—C5—O3	−52.85 (18)
S1—C1—C2—C3	−65.83 (15)	O1—C4—C5—C6	69.89 (16)
S2—C1—C2—S3	−65.04 (13)	C3—C4—C5—C6	−173.23 (13)
S1—C1—C2—S3	59.34 (13)	C19—O5—C6—C5	104.90 (17)
C11—S3—C2—C1	134.39 (12)	O3—C5—C6—O5	−48.42 (19)
C11—S3—C2—C3	−100.37 (12)	C4—C5—C6—O5	71.22 (18)
C1—C2—C3—C4	176.29 (14)	C1—S1—C7—C8	−71.74 (18)
S3—C2—C3—C4	53.74 (17)	C1—S2—C9—C10	68.51 (17)
C1—C2—C3—S4	−57.96 (16)	C2—S3—C11—C12	−71.05 (15)
S3—C2—C3—S4	179.49 (9)	C13'—S4—C13—C14	18.1 (8)
C13—S4—C3—C4	−87.95 (15)	C3—S4—C13—C14	−75.1 (2)
C13'—S4—C3—C4	−121.1 (5)	C13—S4—C13'—C14'	−38.2 (11)
C13—S4—C3—C2	144.51 (13)	C3—S4—C13'—C14'	56.4 (13)
C13'—S4—C3—C2	111.4 (5)	C4—O1—C15—O2	−4.4 (3)
C15—O1—C4—C5	−116.96 (15)	C4—O1—C15—C16	173.80 (15)
C15—O1—C4—C3	119.46 (15)	C5—O3—C17—O4	−3.9 (2)
C2—C3—C4—O1	−160.52 (13)	C5—O3—C17—C18	175.50 (14)
S4—C3—C4—O1	75.30 (15)	C6—O5—C19—O6	8.6 (3)
C2—C3—C4—C5	84.49 (17)	C6—O5—C19—C20	−169.42 (14)