Dange Vijaykumar

Enantiospecific synthesis of (+)-pinguisenol, (+)-pinguisen-10-one and (−)-pinguisen-8,10-dione

The first enantiospecific total synthesis of the sesquiterpene (+)-pinguisenol, the optical antipode of the natural product, and the analogues (−)-pinguisen-10-one and (+)-pinguisen-8,10-dione, starting from R-carvone are described.

Enantiospecific synthesis of (+)-dihydroerythrodiene, (+)-dihydrospirojatamol and (+)-dihydroepispirojatamol

Starting from the monoterpene R-carvone, enantiospecific total synthesis of the spirosesquiterpenes (+)-dihydroerythrodiene, (+)-dihydrospirojatamol and (+)-dihydroepispirojatamol is described.

Facile formation of chiral bicyclo[3.3.1]nonenes via regioselective cyclopropane cleavage of 1-methyltricyclo[4.3.0.02,9]nonan-8-ols☆

Abstract Generation of bicyclo[3.3.1]non-2-enes via a facile, regioselective homo-1,4-elimination reaction of either exo or endo 1-methyltricyclo[4.3.0.0 2,9 ]nonan-8-ols on treatment with pyridine and methanesulfonyl chloride, is described.

A SHORT, VINYL RADICAL CYCLISATION APPROACH TO ()-2-PUPUKEANONE

Addition of tri-n-butyltin radical to a 5-(prop-2-ynyl)bicyclo[2.2.2]oct-2-ene followed by 5-exo-trig cyclisation of the resulting vinyl radical furnishes an isotwistane, providing a short route to the sesquiterpenes, pupukeananes 4 and 2.

A formal total synthesis of (±)-α-pinguisene and (±)-pinguisenol

Formal total synthesis of (+/-)-alpha-pinguisene and (+/-)-alpha-pinguisenol, containing a cia-1,2,6,7-tetramethylbicyclo[4.3.0]-nonane skeleton incorporating two vicinal quaternary carbon atoms and four cis oriented methyl groups on four contiguous carbon atoms, isolated from liverworts is described. Thus, an orthoester Claisen rearrangement of the allyl alcohol 14, obtained from the Hagemanns ester 15, afforded the ene ester 18. Hydrolysis of the ketal and ester moieties transformed the ene ester 18 into keto acid 23. Intramolecular cyclopropanation of the diazo ketone 24 derived from the keto acid 23 afforded a 3 : 2 mixture of chromatographically separable tricyclic diones 25 and 26. Simultaneous regioselective reductive cyclopropane;ring cleavage and reduction of the cyclohexanone carbonyl in the dione 25 with lithium in liquid ammonia furnished the keto alcohol 27, which on Wolff-Kishner reduction followed by oxidation of the alcohol afforded the bicyclic ketone ii, Schinzers precusor of pinguisenol 9 and alpha-pinguisene 10.

An enantiospecific approach to pinguisanes from (R)-carvone. Total synthesis of (+)-pinguisenol

Enantiospecific total synthesis of (+)-pinguisenol 1, a sesquiterpene containing a cis-1,2,6,7-tetramethylbicyclo[4.3.0]nonane carbon framework incorporating two vicinal quaternary carbon atoms and four cis-oriented methyl groups on four contiguous carbon atoms, isolated from a liverwort, is described. The orthoester Claisen rearrangement of the allyl alcohol 9, obtained from (R)-carvone, generates the ester 12. Intramolecular cyclopropanation of the diazo ketone 13, derived from the ester 12, furnishes the tricyclic ketone 7. Degradation of the isopropenyl group followed by regioselective reductive cyclopropane ring cleavage transforms compound 7 into the hydroxy ketone 21. Wolff–Kishner reduction of the hydroxy ketone 21 followed by oxidation and Grignard reaction furnishes pinguisenol (+)-1.

Stereocontrolled synthesis of (±)-α-pinguisene and (±)-pinguisenol

Total synthesis of (±)-α-pinguisene 1 and (±)-pinguisenol 2, employing an orthoester Claisen rearrangement and an intramolecular diazo ketone cyclopropanation reaction for the stereospecific construction of vicinal quaternary carbon atoms, is described.