Chiral synthons from carvone, Part 56. Enantiospecific synthesis of (-)-4-thiocyanatoneopupukeanane

Enantiospecific total synthesis of the natural enantiomer of the marine sesquiterpene (-)-4-thiocyanatoneopupukeanane (6) is described. The bicyclo[2.2.2]octanonecarboxylate 11, obtained from (R)-carvone and methyl methacrylate via Michael-Michael reaction, was transformed into bicyclo[2.2.2]octenecarboxylic acid 8. Intramolecular cyclopropanation reaction of the diazo ketone 7, derived from the acid 8, followed by regioselective reductive cyclopropane ring cleavage generated neopupukeanol 20, which was transformed into (-)-4-thiocyanatoneopupukeanane 6.

Enantiospecific first total synthesis of cucumin-H

Enantiospecific first total synthesis of the linear triquinane sesquiterpene cucumin-H has been described. (R)-Limonene has been employed as the chiral starting material and a combination of Claisen rearrangement, intramolecular cyclopropanation and Nazarov reactions are employed for the regio- and stereospecific construction of the triquinane framework.

Enantiospecific first total synthesis of (6S,7R)-silphiperfolan-6-ol

Enantiospecific first total synthesis of the angular triquinane sesquiterpene (65,7R)-silphiperfolan-6-ol has been accomplished, starting from 2-(3-isopropenyl-2-methylene-1-methylcyclopent-1-yl)acetic acid (readily available from (R)-limonene) employing an efficient, regioselective intramolecular rhodium carbenoid insertion into the CH bond of a tertiary methyl group as the key step. (C) 2012 Elsevier Ltd. All rights reserved.

Enantiospecific First Total Synthesis of ent-Allothapsenol

The enantiospecific first total synthesis of the enantiomer of the irregular sesquiterpene from Ligusticumgrayi allothapsenol, starting from the readily available monoterpene (R)-carvone, is described, which confirmed the assumed absolute configuration of the natural product.