Preparation of 3-amino-3-deoxy-2,4,5,6-tetra-O-methyl-D-altronic acid hydrochloride, a precursor in the preparation of a chiral beta-polyamide (nylon3 analog)

3-Amino-3-deoxy-2,4,5,6-tetra-O-methyl-D-altronic acid hydrochloride was pr epared from methyl 3-azido-3-deoxy-4,6-O-benzylidene-alpha-D-altropyranosid e in seven steps. The key intermediate in this synthesis was the 3-acetamid o-3-deoxy-2,4,6-tri-Omethyl-D-altrono-1,5-lactone which could be transforme d, in one step, into methyl 3-acetamido-3 -deoxy-2,4,5,6-tetra-O-methyl-D-a ltronate. However, attempts to open the 3-azido-3-deoxy-tri-O-methyl (or O- benzyl)-D-altrono-1,5-lactone intermediates gave a mixture of products, mos tly, alpha,beta-unsaturated carbonyl compounds. The 3-amino-3-deoxy-2,4,5,6 -tetra-O-methyl-D-altronic acid could be transformed into the corresponding beta-lactam, (3S,4R)-3-methoxy-4-(D-erythro-trimethoxypropyl) azetidine-2- one, which was further polymerized by anionic ring-opening polymerization g iving poly[(2S,3R)-2-methoxy-3-(D-erythro-trimethoxypropyl) propanamide], a chiral nylon 3 analog.