Nitrous acid deamination of acyclic, polyfunctional systems. Part 3. Vicinal participation in the nitrous acid deamination of chiral 1-thio-2-aminoalkanepolyols: the deamination of 2-amino-2-deoxy-D-glucose ethylene and propan-1,3-diyl dithioacetals, and the crystal and molecular structure of 1,2-SS′-ethylene-5,6-O-isopropylidene-1,2-dithio-α-D-mannofuranoside

Abstract

Deamination of 2-amino-2-deoxy-D-glucose ethylene dithioacetal (1) at pH 5.6, followed by acetylation of the product, gave an 8 : 40 : 3 mixture of 3,5,6-tri-O-acetyl-1,2-SS′-ethylene-1,2-dithio-α-D-mannofuranoside (5b), 3,4,6-tri-O-acetyl-1,2-SS′-ethylene-l,2-dithio-α-D-mannopyranoside (4b), and 3,5,6-tri-O-acetyl-2-deoxy-D-arabino-hexono-1,4-lactone (2b). Deamination of (1) at pH <1 by use of dinitrogen trioxide followed by acetylation gave the lactone (2b) essentially exclusively. Similar treatment of the propan-1,3-diyl analogue (3) of (1) at pH <1 also gave the lactone (2b) : at pH 5.6 the main product was 3,5,6-tri-O-acetyl-1,2-SS′-(propan-1,3-diyl)-1,2-dithio-α-D-mannofuranoside (7b). Structural assignments were based on formation of the 5,6-isopropylidene acetals [(8) and (10)] from the non-acetylated precursors of (5b) and (7b), by ¹H n.m.r. spectroscopy at 250 MHz for compounds (2b), (4b), (5b), (7b), (8), and (10), and by electron-impact mass spectrometry. An X-ray crystal structure-determination conducted on 1,2-SS′-ethylene-5,6-O-isopropylidene-1,2-dithio-α-D-mannofuranoside (8) permitted unambiguous assignment of the ring size, relative stereochemistry, and favoured conformation of this strained molecule. The reaction course and product distribution in the deamination were monitored and quantitated by g.l.c.–mass spectrometry of the corresponding per-trimethylsilylated derivatives and are discussed from preparative and mechanistic standpoints.