NITROUS-ACID DEAMINATION OF ACYCLIC, POLYFUNCTIONAL SYSTEMS .3. VICINAL PARTICIPATION IN THE NITROUS-ACID DEAMINATION OF CHIRAL 1-THIO-2-AMINOALKANEPOLYOLS - 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-ALPHA-D-MANNOFURANOSIDEY