Synthesis of Novel Iso-4'-thionucleosides Using the Mitsunobu Reaction.
A novel class of isomeric 4'-thionucleosides with the base moiety at the 2'-position was synthesized from D-glucose. The coupling of 1,4-anhydro-4-thioarabitol (13) with various nucleobases using the Mitsunobu reaction was investigated. With both purines and N(3)-benzoyluracils, the reaction predominantly gave beta-isomers, suggesting that these were produced via an episulfonium intermediate. The beta-anomers produced by the reaction of N(3)-benzoyluracils included both N- and O-alkylated derivatives. Interestingly, only the reaction of N(3)-benzoyluracil gave a mixture of N-alkylated adduct (20d) and O-alkylated bipyrimidinyl adduct (22), the structure of which was unambiguously determined by NMR spectroscopic data including HMBC and NOE. Deprotection of the Mitsunobu reaction products gave the desired iso-4'-thionucleosides.
Yamada
Kohei
K
Biochemicals Division, Yamasa Corporation, 2-10-1 Araoicho, Choshi, Chiba 288-0056, Japan.
Sakata
Shinji
S
Yoshimura
Yuichi
Y