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

AminoScience Laboratories, Ajinomoto Co., Inc., Kawasaki-ku, Kawasaki, Japan.
Nucleosides Nucleotides &amp Nucleic Acids (Impact Factor: 0.89). 02/2006; 25(4-6):625-34. DOI: 10.1080/15257770600686279
Source: PubMed

ABSTRACT 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. The coupling product was then successfully transformed into the known antiviral agents in a short number of steps.