Improved industrial syntheses of penciclovir and famciclovir using N2-acetyl-7-benzylguanine and a cyclic side chain precursor.
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.
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ABSTRACT: A new expeditious method for the homo-conjugate addition of nitrogen heteroaromatics to 1,1-cyclopropanedicarboxylates was developed in the presence of La(OTf)3 as an efficient Lewis acid catalyst under microwave irradiation.Tetrahedron Letters 10/2008; 49(41). DOI:10.1016/j.tetlet.2008.07.142 · 2.39 Impact Factor