RAMAN-SPECTROSCOPIC DETERMINATION OF THYMIDINE NUCLEOSIDE STRUCTURES IN NUCLEOTIDES

Several spectral differences in Raman spectra were observed for thymid ine (TM), 3'-O-acetylthymidine (3'OATM), 3',5-di-O-acetylthymidine (3' 5'DOATM), thymidine 5'-monophosphoric acid (H(2)TMP) and its Ca2+, Sr2 + and Ba2+ salts owing to nucleoside conformational differences in the thymidine moiety, The spectroscopic characterization of the nucleosid e structures was made on the basis of previous crystallographic works relative to TM, 3'O ATM, 3'5/DOATM and Ba(TMP). 6H(2)O. The crystal st ructures of the other compounds reported here are, as vet, unknown, Ho wever, their nucleoside structures were inferred from the position of the phosphoester stretching band, The results show that C(2')-endo-ant i, C(3')-endo-anti and C(2')-endo/C(3')-exo-anti puckers generate mark er bands useful to characterize and titrate these thymidine nucleoside conformations, The furanose sugar puckering of the C(Z')-endo-anti ge ometry has been suggested to account for the enhanced activity of thym idine derivatives against human immunodeficiency virus-type 1, A Raman spectroscopic method is described for the determination of this struc ture in thymidine nucleosides and nucleotides.