Action of ammonia on the methyl 2,3-anhydro-d-ribofuranosides, and treatment of the products with nitrous acid

The reaction between methyl 2,3-anhydro-5-O-p-nitrobenzoyl--ß-d-ribofuranoside (2) and ammonia gives mainly the d-xylo amine 3, as previously reported. Azide ion shows similar regioselectivity with methyl 2,3-anhydro--ß-d-ribofuranoside (1). Ammonia reacts with methyl 2,3-anhydro-5-O-p-nitrobenzoyl-a-d-ribofuranoside (11) to give the d-arabino amine 12 and d-xylo amine 13 in the ratio 2:1. Both isomers were obtained crystalline after chromatography on Dowex 1 (HO^- resin. With nitrous acid, 3, 13, and 12 each yield the parent epoxide, together with other products. In particular, 12 gives 2-O-methyl-d-ribose 14 as the major product; the structure of 14 was proved by synthesis of the enantiomer 21. Conformational aspects of the deaminations are discussed. © 1977.