Preparation of methyl 4,6-di-O-acetyl-3-C-nitro-2-enopyranoside derivatives and their reduction with sodium borodeuteride

The conformationally flexible title compounds were prepared and subjected to reduction with sodium borodeuteride. Deuteride ion attacks exclusively from the side opposite of the anomeric methoxyl group. However, the stereoselectivity of a similar reduction of the corresponding 4,6-O-benzylidene-β-d-threo-2-enopyranoside derivative, adopting the 0H5 conformation, was exceptionally low, suggesting that reduction of the 4,6-diacetate having the β-d-threo configuration did not occur from the stable 0H5 conformation, but from an unstable ((5H0) one.