Synthesis of Anti-Angiogenic Isocoumarins

A concise synthetic route has been developed for the preparation of the naturally occurring isocoumarin cytogenin and NM-3, an analogue with anti-angiogenic activity. The route is general and also provided C(3) side chain modified analogues. Key aspects of the synthesis include orthogonal protection of the two aromatic alkoxy groups, benzylic lithiation and carboxylation, use of the resulting carboxylic acid in a DCC-promoted acylation of Meldrum's acid, and facile ester enolate alkylations for introduction of side chains for convenient generation of a new set of NM-3 analogues.