Synthesis of polyhydroxy amino acids based on d- and l-alanine from d-glycero-d-gulo-heptono-1,4-lactone

2-Amino-2,3-dideoxy-d-manno-heptonic acid (7) has been synthesized from 2,5,6,7-tetra-O-acetyl-3-deoxy-d-gluco-heptono-1,4-lactone (1), which was readily prepared from d-glycero-d-gulo-heptono-1,4-lactone. O-Deacetylation of 1 followed by treatment with 13:1 (v/v) 2,2-dimethoxypropane/acetone in the presence of p-toluenesulfonic acid gave methyl 3-deoxy-4,5:6,7-di-O-isopropylidene-d-gluco-heptonate (3) as a crystalline product (80% yield). The free hydroxyl group (OH-2) of 3 was mesylated and substituted by azide to give the corresponding azide derivative 5. Hydrogenolysis and further hydrolysis of the ester function of 5 afforded α-amino acid 7 (43% overall yield from 1). Compound 7 is an analog of l-alanine having a polyhydroxy chain attached to C-3. The diastereoisomer of 7 at C-2, 2-amino-2,3-dideoxy-d-gluco-heptonic acid (12) was also prepared from 3, by a route that involved 2,3-dideoxy-2-iodo derivative 8 as a key intermediate.

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