Synthesis of polyketide-type aromatic natural products by biogenetically modeled routes

2.24 – Pyrans and Fused Pyrans: (iii) Synthesis and Applications

Pyrans and their Benzo Derivatives - Synthesis

A new approach to the synthesis of 3,6- and 5,6-dialkyl derivatives of 4-hydroxy-2-pyrone. Synthesis of rac-germicidin

Publisher Summary This chapter focuses on dehydroacetic acid, triacetic acid lactone, and related pyrones. Dehydroacetic acid is mainly used to produce clopidol, a coccidiostatic agent. Small quantities are used as a preservative for fruits and vegetables as well as a stabilizer for plastics. Its sodium salt is also of interest for these applications. 4-Hydroxy-6-methyl-2-pyrone (triacetic acid lactone) is a natural product of polyketide origin. Its 3-acetyl derivative, 3-acetyl-4-hydroxyd-methyl-2-pyrone (dehydroacetic acid), has been isolated from natural sources and is industrially available by dimerization of diketene. Preparation of pyrones dealt with in the chapter can be achieved by modifying previously existing pyrones or by cyclizing open-chain compounds. Biogenetic formation of triacetic acid lactone has been considered a derailment from fatty acid biosynthesis promoted by the absence of the reductant NADPH. The pyrones react at their different ring positions.

M.P. Wachter

Papers

Condensations at the 6α-position of triacetic lactone via the dianion

Condensations of dehydroacetic acid at the 6-methyl position

Aromatization reactions of 4-hydroxy-6-phenacyl-2-pyrone and related compounds