Synthesis of the four 1-(1-deoxy-D-pentitol-1-yl)thymines and conformational properties of the acyclic sugar chain

Acetylated D-pentose diethyl dithioacetals were coupled by way of 1-bromo-1-ethylthio derivatives with 2,4-bis(trimethylsilyl)thymine to afford diastereomeric pairs of acyclic-sugar nucleoside analogues bearing a thymin-1-yl and an ethylthio group at C-1. Free-radical desulfurization by the action of tributylstannane removed the ethylthio group to afford the corresponding acetylated 1-(1-deoxy-d-pentitol-1-yl)thymines and subsequently the free title compounds in the arabino, lyxo, ribo, and xylo series. Conformations of the intermediates and products were studied in detail and the final products were evaluated for their potential as agents active against plant viruses and rice blast fungus.