Drimanic sesquiterpenoid synthesis

Heterocycles in synthesis of drimane sesquiterpenoids from labdane diterpenoids 97IZV896. 

The diverse biological activity (e.g. insect antifeeding, plant growth regulation, molluscicidal) of a number of drimane sesquiterpenoids has stimulated considerable interest in their synthesis and the year under review has seen many new developments and improvements. Much of the synthetic work has centred around the key bicyclic diester (54) derived from 1-vinyl-2,6,6-trimethylcyclohexene and dimethyl acetylenedicarboxylate. In contrast to earlier results,34 Ley et al.8S... 

In this review, the results of our investigations in the field of the synthesis of a number of optically-active, drimanic compounds from norlabdanic derivatives, the cleavage products of many available labdanoids, and also from a mixture of neoabienols (7) are summarized. The respective literature data are also discussed in the present article. A number of the prepared drimanes are naturally occurring biologically active substances. Others have been used as intermediates in the syntheses of important natural bioactive polyfunctional drimane sesquiterpenoids. Below the syntheses of the representatives of the drimane (1) group are described. 

We accomplished the drimenol (2) synthesis from the sclareol (3) [44] (Scheme 9). This was the first synthesis of a drimanic sesquiterpenoid... 

Sesquiterpenoids possessing the drimane skeleton (22) exhibit an impressive series of biological properties. Recently, all aspects relative to occurrence [76], biological activity [76], insect antifeedant properties [77] and synthesis [78] of these terpenoids have been exhaustively reviewed. 

TOTAL SYNTHESIS OF BIOLOGICALLY INTRIGUING DRIMANE-TYPE SESQUITERPENOIDS VIA INTRAMOLECULAR DIELS-ALDER APPROACHES... 

Follotving the quite recent discovery of the broad range of biological activities exhibited by members of the sesquiterpene-based drimane family, namely mnio-petals, kuehneromycins, and marasmanes, a solid-phase approach towards a common key intermediate has recently been disclosed [408]. This supported synthesis offers the additional advantage of potential access to libraries of compounds with the same sesquiterpenoid skeleton. 

Total Synthesis of Biologically Intriguing Drimane-Type Sesquiterpenoids Via Intramolecular Diels-Alder Approaches... 

The robustness of the method was further demonstrated by Yang and co-workers, who used it first in the synthesis of drimane-type sesquiterpenoids such as marasmene (40, Scheme 14) [108]. In this case, the required ketoester was obtained via conjugate addition of an organocuprate onto Michael acceptor 37. Later, Yang and co-workers also used the methodology for the synthesis of compounds 41 and 42 used in the total syntheses of (—)-lingzhiol and a fragment of azadirachtin, respectively [109, 110]. 

In 2011, Yang and coworkers developed a unified strategy for the synthesis of drimane-type sesquiterpenoids based on an enabling gold-catalyzed tandem reaction (Scheme 13.26) [31], This strategy accomplished the first total synthesis of maras-mene and other analogs of drimane-type sesquiterpenoids. 

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