Nucleotides. VI. Syntheses and spectral properties of some deazaadenylyl-deazaadenosines (dinucleoside monophosphates with unusual CD-spectrum) and closely related dinucleoside monophosphates.

Nine dinucleoside phosphates containing 1-deaza-(1A) and 3-deazaadenosine (3A) were prepared. Hypochromicity and CD spectra of these dimers were determined. It was found that varying degrees of base-stacking are operative with these oligonucleotides and their CD spectra fall into three classes. The first class CD spectra which are more or less similar in profile to those of adenylyl-(3'-5')-adenosine includes the CD spectra of 1A2'p5'A, 1A3'p5A, 3A2'p5'A and 3A3'p5'A. The second class includes the CD spectra of A2'p5'1A and A3'p5'1A whose characteristic is that the positive Cotton band appears in the range of 280-310 nm. The third type CD spectra has the characteristics that the negative Cotton band appears in the longer wavelength region and th CD spectra are similar in profile to those of L-adenylyl-(3'-5')-L-adenosine which has the "left-handed helical" conformation. The CD spectra of A2'p5'3A, A3'p5'3A and 3A3'p5'A belong to this class. Another salient observation emerging from the CD-determination is that 3A3'p5'3A has the spectrum quite different from that of poly 3-deazaadenylic acid.