Abstract: | The conformational preference of the thymine base ring with respect to the sugar ring in β,β,β,-trichloroethyl 5′amino-5′-deoxythymidine-5′-phosphate has been studied by 13C n.m.r. spectroscopy. The magnitude of the three bond vicinal coupling constant, J(C-2, H-1′), for β,β,β-trichloroethyl 5′-amino-5′-deoxythymidine-5′-phosphate and the similarity between the chemical shifts for the furanose carbons C-1′, C-2′, and C-3′ in β,β,β-trichloroethyl 5-′-amino-5′-deoxythymidine-5′-phosphate and in β,β,β-trichloroethyl thymidine 5′-phosphate indicate that the amino analogue exists in aqueous solution predominantly in the anti conformation, as is the case with natural nucleotides. |