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. 63, 432 (1985). Several methyl 6-deoxy-, 6-deoxy-6-halo-, and 6-0-p-tolylsulfonylhexopyranoside 2-and 4-p-toluenesulfonates reacted readily with lithium triethylborohydride in boiling tetrahydrofuran under reductive dcsulfonyloxylation at C-2 and C-4, respectively, and with reduction at C-6 whcre applicable. The desulfonyloxylations procceded with ring contraction to furnish, in 40-60% isolated yields, new branched-chain pentofuranoside derivatives, namely, methyl 2.5-dideoxy-2-C-(hydroxymethyl)pentofuranosidcs having the a-~-xj~lo, a-D-xj~lo, and a-D-ribo configurations (from 2-tosylatcs), and methyl 3.5-dideoxy-3-C-(hydroxymethyl)pentofuranosides having the a-D-arabitzo and a-D-ribo configurations (from 4-tosylatcs). In some of the reactions, reductively desulfonyloxylated but unrearranged products were formed in addition. Methyl 4,6-0-benzylidene-2,3-di-O-p-tolylsulfonyl-a-~-gaactopyranoside reacted by partial de-0-sulfonylation and partial desulfonyloxylation, with and without ring contraction, to give methyl 3.5-0-benzyIidcne-2-deoxy-2-C-(hydroxymethyl)-a-~-/~~xo-pentofuranoside, methyl 4,6-0-benzyIidene-3-deoxy-a-~-/yxo-hexopyranosidc, and the parent 2.3-diol.

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