An Enantiospecific Approach to Tricyclic Sesquiterpenes Mayurone and Thujopsenes¹

Abstract

An enantiospecific approach to mayurone and thujopsenes, sesquiterpenes containing three contiguous quaternary carbon atoms, starting from (R)-carvone (8), is described. (S)-3,4,4-Trimethylcarvone (7), obtained from (R)-carvone, was transformed into the bicyclo[2.2.2]octanone 13 via regioselective intramolecular alkylation of the allyl bromide 11. Regioselective ozonolysis and Criegee fragmentation of the bicyclic ketone 13 furnished the keto ester 14. Reductive deoxygenation followed by one-carbon homologation transformed the keto ester 19 into the ester 6. Intramolecular cyclopropanation of the diazo ketone 25, derived from the acid 5, furnished (-)-dihydromayurone (4), thus constituting a formal enantiospecific synthesis of mayurone and thujopsenes.

Chemical Composition, Antioxidative and Anticancer Activities of the Essential Oil: Curcumae Rhizoma–Sparganii Rhizoma, a Traditional Herb Pair

“…Interestingly, 2-ethylhexyl-salicyate, a significant sunscreen, was widely used in cosmetics and the medicine industry [34]. Mayurone was first reported from Mayur pankhi and Thujopsis dolabrata , respectively, in 1965, and widely existed in many kinds of plants such as Panax ginseng and Franco Thujaorientalis [35]. Considering the relatively high content and potential activity of those new components, it is inferred that they may impact on the activity and efficacy of HP oil.…”

Rearrangements of organic peroxides and related processes

“…In the last years, new enantiospecific approaches for the synthesis of sesquiterpenes 162 from ketone 161 were developed [ 301 – 307 ]. In these methods, the Criegee rearrangement represents one key step and one example is presented in Scheme 48 [ 303 ].…”

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

“…One enantiospecific total synthesis of (+)-thujopsene ( 10 ) by Srikrishna and Anebouselvy began with ( R )-carvone ( 11 ) (Scheme 2) [33]. During the total synthesis, the authors prepared carboxylic acid (+)- 12 over a 14-step sequence.…”