Abstract
The first synthesis of 4-amino-4-deoxy- d-hexuronic acid has been achieved. Tritylation of methyl 4-azido-4-deoxy-α- d-glucopyranoside ( 1) gave the 6-trityl ether ( 2) which was converted into its 2,3-dibenzoate ( 3) and deritylated to methyl 4-azido-2,3-di- O-benzoyl-α- d-glucopyranoside ( 5). Oxidation of 5 afforded the glucuronic acid derivative 6 which upon esterification to 7, followed by reduction and benzoylation yielded methyl (methyl 4-benzamido-2,3-di- O-benzoyl-4-deoxy-α- d-glucopyranosid)uronate ( 8), the structure and conformation of which were firmly established by n.m.r. analysis. De-benzoylation of methyl (methyl 4-azido-2,3-di- O-benzoyl-4-deoxy-α- d-glucopyranosid)uronate ( 7) with sodium methylate to 9, followed by de-esterification and subsequent hydrogenation afforded crystalline methyl 4-amino-4-deoxy-α- d-glucopyranosiduronic acid ( 11), the structure of which was established by esterification and benzoylation to 8. N-Acetylation of 11 yielded methyl 4-acetamido-4-deoxy-α- d-glucopyranosiduronic acid ( 14) which was esterified and peracetylated to the methyl ester 16. Derivative 16 was also obtained by hydrogenation and peracetylation of 9. Epimerization at C-5 was not observed in the conversion of 7 → 11, which suggests that a total synthesis of the gougerotin-derived C-substance from the 4-amino-4-deoxy-hexuronic acid derivatives reported herein is feasible.
Published Version
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