T. Jagadeeswar Reddy

Reduction of quinolines to 1,2,3,4-tetrahydro derivatives employing a combination of NaCNBH3 and BF3.OEt2

A regiospecific reduction of quinolines (and 1,10-phenanthroline) into the corresponding 1,2,3,4-tetrahydro derivatives using a combination of sodium cyanoborohydride and boron trifluoride etherate in refluxing methanol is described. Under the same conditions indole and acridine reduced to the corresponding dihydroderivatives, whereas acyl group transfer from oxygen to nitrogen atom is also noticed in the case of 8-acyloxyquinolines.

STEREOSELECTIVE TOTAL SYNTHESIS OF ()-TOCHUINYL ACETATE AND ()-DIHYDROTOCHUINYL ACETATES

Details of the first total synthesis of the marine natural product dihydrotochuinyl acetate is described. Cyclopentenone annulation of p-methylacetophenone via a Claisen rearrangement-Wacker oxidation based sequence generated the cyclopentenone 3, a known precursor for the sesquiterpenes cuparene, laurene, α-cuparenone and β-cuparenones. Conversion of the ketone moiety into a carboxylate followed by stereoselective alkylation and reduction transformed the cyclopentenone 3 into the primary alcohol 19. Birch reduction of the alcohol 19 followed by acetylation furnished (±)-dihydrotochuinyl acetate, whereas direct acetylation of 19 furnished (±)-tochuinyl acetate.

A stereoselective total synthesis of bakkenolide-A (fukinanolide)

A highly stereoselective synthesis of bakkenolide-A (fukinanolide. 1a) employing the radical mediated spirannulation methodology is 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.

Enantioselective synthesis of both (+)- and (-)-derivatives of bicyclo[4.3.0]nonan-8-one and 3,8-diones from R-carvone

Enantioselective synthesis of both the enantiomeric forms of the hydrindane derivatives mentioned in the title, potential chiral precursors in terpenoid synthesis, starling from R-carvone employing two different cyclopentannulation methodologies is described.

Enantiospecific synthesis of (+)-(1S,2R,6S)-1,2-dimethylbicyclo[4.3.0]nonan-8-one and (−)-7-epibakkenolide-A☆

Synthesis of the chiral bicyclic ketone mentioned in the title starting from R-carvone, and its elaboration to 7-epibakkenolide-A is described. Conjugate addition of dimethyl copperlithium to R-carvone followed by alkylation of the intermediate enolate generated the allylated compound 6, which was transformed into the diketone 12 via a sequence of reactions comprising regiospecific Wacker oxidation, ozonation-Criegee rearrangement as key reactions. Intramolecular aldol condensation followed by catalytic hydrogenation converted the diketone 12 into the bicyclic ketone (+)-3, the optical antipode of the compound derived from the sesquiterpenes bakkenolide-A and fukinone. A 5-exo-dig radical cyclisation based strategy transformed the bicyclic ketone 3 into chiral 7-epibakkenolide-A.

Carvone based approaches to chiral functionalised C-ring derivatives of taxanes☆

Enantiospecific synthesis of functionalised chiral C-ring derivatives of taxanes, starting from R-carvone, is described.

Synthesis of taxanes—the carvone approach; a simple, efficient stereo- and enantio-selective synthesis of the functionalised A ring

A highly stereo-and enantio-selective methodology for the construction of the chiral functionalised A-ring of taxanes, starting from (R)-carvone employing a short, simple and efficient sequence is described.

Carvone based approaches to chiral functionalised B-seco-taxanes†

Starting from (R)-carvone, the synthesis of chiral, functionalised C-aromatic-B-seco-taxanes and an extension to the synthesis of a B-seco-20-nortaxane derivative have been described.

A formal total synthesis of (±)-homogynolide-B

A formal total synthesis of (±)-homogynolide-B, a sesquiterpene containing an α-spiro-β-methylene-γ-butyrolactone moiety spirofused to a bicyclo[4.3.0]nonane framework, is described. Thus, Hagemann’s ester 11 was converted into the allyl alcohol 16 in three steps. One-pot Claisen rearrangement of the allyl alcohol 16 and 2-methoxypropene in the presence of a catalytic amount of propionic acid afforded a 3∶2 epimeric mixture of the ketone 15 and further rearranged product 19. Ozonolysis followed by intramolecular aldol condensation and hydrogenation transformed the enones 15a,b into the key intermediate keto ketals 13a and 13b. Methoxymethylene Wittig reaction followed by bromoacetalisation converted the keto ketal 13a into the radical precursor bromo acetal 22a. The 5-exo-dig radical cyclisation of the bromo acetal 22a, followed by acid catalysed hydrolysis and oxidation, led to the keto spirolactone 12, Greene’s precursor of homogynolide-B. The same sequence transformed the keto ketal 13b into a 3∶2 mixture of the spirolactones 12 and 25, which on equilibration furnished the spirolactone 12. The stereostructure of the keto spirolactone 12 was unambiguously established by single-crystal X-ray diffraction analysis.