Synthetic Approach to Aklavinone Using 2-Oxo-2H-pyran-5-carboxylate (Coumalate) Intermediates

Article abstract of DOI:10.1021/jo00386a002

A novel approach for the preparation of aklavinone 5 is described in which the key step is the cycloaddition of a substituted coumalate with a ketene acetal to produce a masked A ring with the C and D rings attached.The 4-(arylmethyl)coumalate 53 was prepared from naphthalene-1,5-diol (6) by a seven step route involving as the key step the cyclocondensation of the methyl (arylmethyl)propiolate 52 with methyl 3-oxopentanoate 10.Cycloaddition of 53 with dimethyl ketene acetal 12 produced the potential A-ring precursor 67, which could not be cleanly reduced, thereby ending this scheme.The preparation of functionalized 4,6-dialkylpyrone-5-carboxylates and their use in the synthesis of bicyclic lactones and substituted benzoates via cycloaddition reactions are also described.