Pentalenolactone intermediate

This strategy [20b] has been applied, for instance, in a total synthesis of pentalenolactone E methyl ester (27) (Scheme 5.17), and more recently Marino and Long [20c] have described the intramolecular version of this annulation procedure to synthesise an octahydronaphthalene derivative (28) which is a key intermediate for a new synthesis of dihydrocompactin (Scheme 5.18). However, the reaction with aldehydes affords only very low yields of a mixture of lactones. 

The product (2) is an intermediate in a synthesis of pentalenolactone E methyl ester (3), a sesquiterpene antibiotic.2... 

An ingenious stereocontrolled synthesis of pentalenolactone (300) has been recorded by Danishefsky et in which three of the five chiral centres are incorporated into a key tetracyclic intermediate (Scheme 45). Two other... 

Hua has used the products of Pauson-Khand cycloadditions for syntheses of optically active pental-enene and racemic pentalenolactone E methyl ester. The racemic ketone in the first case was converted to the necessary optically active intermediate by kinetic resolution via 1,4-addition of an optically active allyl sulfoxide anion. These represented the first synthesis of natural products containing the angularly fused triquinane skeleton from bicyclic Pauson-Khand products (equation 53 and Scheme 20). ... 

An application of this methodology is the preparation of a key intermediate in the synthesis of the methyl ester of ( )-pentalenolactone E (22) by the use of palladium-catalyzed metallo-ene cycl iza tion/methoxyca r bony la tio n7 °. 

Danishefsky s pentalenolactone synthesis used (13) as an intermediate. Immediate Diels-Alder disconnection is no good as it produces the unlikely starting materials (14) and (15). If we first remove the acetal to give diol (16), this could be made from alkene (17). Diels-Alder disconnection is still impossible—(18) is too strained — but a minor FGI allows a good Diels-Alder reaction between (19) and cyclopentadiene. 

C15H24, Mr 204.36, oil, a sesquiterpene hydrocarbon of the triquinane type from cultures of Streptomyces griseochromogenes and S. UC 5319. It is the first isolable biosynthetic intermediate in the pathway from farnesyl pyrophosphate to the antibiotically active pentalenolactones. ... 

Details of the Danishefsky group s synthesis of pentalenolactone have appeared and Heathcock and Plavac have reported the synthesis of (110), a key intermediate in their own approach to pentalenolactone. ... 

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