Pentofuranosides, 2,3-anhydro

A satisfactory result was obtained in AgOTf- or NIS/TfOH-activated condensation of S-benzothiazolyl pentofuranosides 93, 94 and 95 with l,2 3,4-di-isopropylidene-a-D-galactopyranose 96 and l,6-anhydro-3,4-isopropylidene-P-D-galactopyranose 97 as the acceptor to afford the corresponding disaccharides in moderate to good yields and stereoselectivity [445],... 

Similar empirical assignments have been made by Hough and Shute for the acetates of 2,5-anhydro-l-deoxy-l-nitroheptitols (3) and (4), and by Hall and Perry for the acetylated methyl pentofuranosides (5), (6), (7), and (8). These assignments are all empirical and do not appear to be indicative of conformation. 

Anhydro-l,4-di-0-benzyl-L-threitol on reaction with allylmagnesium bromide, osmium tetroxide, sodium periodate then HCl affords methyl 3-C-(benzyloxymethyl)-2,3-dideoxy-L-r/ireo-pentofuranoside as a useful intermediate for the synthesis of 2 3 -dideoxy-3 -C-(hydroxymethyl)-4 -thionucleosides. In an alternative route to such nucleosides the intermediate branched-sugar 50 was prepared in which the hydroxymethyl group was introduced into the 3-position by a light-induced addition of methanol to 6-O-rerr-butyldimethylsilyl-D-g/yceru-pent-2-eno-1,4-lactone (see Vol. 26, p. 242, ref. 159). ... 

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