Guaianolide sesquiterpenes synthesis

Methylenation. In a synthesis of the two guaianolide sesquiterpenes dehydrocostus lactone (4) and estafiatin (6), usual methods for methylenation of the ketone group of 2 resulted only in p-elimination. However, use of the anion of 1 effected the desired reaction, albeit in modest (15%) yield. 

Synthesis of 6,12-sesquiterpenolides This section describes the synthesis of sesquiterpenes bearing a lactone moiety between C(6) and C(12). The transformation of the A-ring in santonin to give eudesmanolides, guaianolides, and elemanolides, as well as the modification of the lactone ring is described. Some microbiological transformations of santonin and its derivatives are also described. 

A review has recently appeared describing the synthesis of hydroazulene sesquiterpenes through rearrangement of substituted hydronaphthalene precursors, including some syntheses of guaianolides from santonin (1)... 

The continued search for novel synthetic routes to the sesquiterpene pseudo-guaianolides has resulted in several new approaches to the hydroazulene ring system. Lansbury and Serelis have shown that the hydroxycyclopentanone (191) undergoes facile cationic cyclization on treatment with formic acid, leading directly to the hydroazulenedione (192). Further manipulation of (192) led to the total synthesis of damsinic acid (193). In an impressive synthesis of the closely... 

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