HYDROXYMETHYL-ALPHA-L-THREO-PENTOFURANOSYL)URACILS

ene-4-C-hydroxymethyl-alpha-L-lyxofuranosyl)uracil (I) was converted i n seven steps into -hydroxymethyl-alpha-L-threo-pentofuranosyl)uracil (8) and further into isoprapylidene-alpha-L-threo-pentofuranosyl)uraci l (9). Successive benzoylation, removal of the isopropylidene group, r eaction with acetaldehyde diethyl acetal, and debenzoylation afforded (R)- and -hydroxymethyl-alpha-L-threo-pentofuranosyl)uracil (10a and 1 0b, respectively). Reaction of ethyloxymethyl-alpha-L-threo-pentofuran osyl)uracil (14) with dichloromethane under conditions of phase transf er, followed by detritylation, afforded -O-methylidene-alpha-L-threo-p entofuranosyl)uracil (15). Compound 14 was obtained from the derivativ e 8 by partial silylation, tritylation and desilylation. The absolute configuration of the isomeric ethylidene derivatives 10a and 10b was d etermined by NMR spectroscopy and the population of the deoxypentofura nose ring conformers was derived from the vicinal coupling constants I (H,H). The obtained results were compared with energy calculations. Ne ither of the prepared nucleoside analogues was active in vitro against HIV-I and HIV-2.