Improved industrial syntheses of penciclovir and famciclovir using N2-acetyl-7-benzylguanine and a cyclic side chain precursor.

We have established practical synthetic methods for penciclovir (PCV, 1) and famciclovir (FCV, 2) from N2-acetyl-7-benzylguanine (NAc7BnG, 3) and 6,6-dimethyl-5, 7-dioxaspiro[2.5]octane-4,8-dione (4)--the latter being a more easily prepared cyclic precursor of the diacetate side chain (5) used in the conventional process. The coupling of 4 with 3 proceeded regioselectively at the N9 position of guanine in good yield.

New approaches to the industrial synthesis of HIV protease inhibitors.

Efficient and industrially applicable synthetic processes for precursors of HIV protease inhibitors (Amprenavir, Fosamprenavir) are described. These involve a novel and economical method for the preparation of a key intermediate, (3S)-hydroxytetrahydrofuran, from l-malic acid. Three new approaches to the assembly of Amprenavir are also discussed.

Synthesis of optically active alpha-aminoalkyl alpha'-halomethyl ketone: a cross-Claisen condensation approach.

A simple and versatile method was developed for the synthesis of alpha-aminoalkyl alpha'-halomethyl ketone derivatives, which are useful intermediates of protease inhibitors. It involves selective halogenation of the alpha-position on a beta-ketoester, which is prepared by cross-Claisen condensation using N-protected amino acid ester. The title compound is obtained in high yield after decarboxylation of the alpha-halo-beta-ketoester.