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 β-Polyamide (Nylon 3 Analog)

ABSTRACT

3-Amino-3-deoxy-2,4,5,6-tetra-O-methyl-D-altronic acid hydrochloride was prepared from methyl 3-azido-3-deoxy-4,6-O-benzylidene-α-D-altropyranoside in seven steps. The key intermediate in this synthesis was the 3-acetamido-3-deoxy-2,4,6-tri-O-methyl-D-altrono-1,5-lactone which could be transformed, in one step, into methyl 3-acetamido-3-deoxy-2,4,5,6-tetra-O-methyl-D-altronate. 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, mostly, α,β-unsaturated carbonyl compounds. The 3-amino-3-deoxy-2,4,5,6-tetra-O-methyl-D-altronic acid could be transformed into the corresponding β-lactam, (3S,4R)-3-methoxy-4-(D-erythro-trimethoxypropyl) azetidine-2-one, which was further polymerized by anionic ring-opening polymerization giving poly[(2S,3R)-2-methoxy-3-(D-erythro-trimethoxypropyl) propanamide], a chiral nylon 3 analog.