Synthesis of Cembranoid Analogues through Ring-Closing Metathesis of Terpenoid Precursors: A Challenge Regarding Ring-Size Selectivity was written by Heidt, Tanja;Baro, Angelika;Koehn, Andreas;Laschat, Sabine. And the article was included in Chemistry – A European Journal in 2015.Formula: C12H18O3 The following contents are mentioned in the article:
A systematic study on ring-closing metathesis with Grubbs II catalyst to cembranoid macrocycles is described. Acyclic terpenoids I [X = OTBS, H, OH, etc.; R = Me, Et, iPr, etc., R1 = H, Me, Et, etc.] with a functional group X in the homoallylic position relative to an RCM active terminus and substituents R, R1 directly attached to the other terminal double bond were prepared from geraniol derived trienes and fragments that are based on bromoalkenes and di-Me malonate. Such terpenoids were suitable precursors, despite the presence of competing double bonds in their framework. The size of R and R1 is crucial for successful macrocyclization. Whereas small alkyl substituents at the double bond directed the RCM towards six-membered ring formation, cross metathesis leading to dimers dominated for bulkier alkyl groups. A similar result was obtained for precursors without functional group X. In the case of unsym. substituted terpenoid precursor I [R = Et, R1 = Me] with homoallylic OTBS or OMe group, the RCM could be controlled towards formation of macrocyclic cembranoids, which were isolated with excellent E-selectivity. The role of the substituents was further studied by quantum chem. calculations of simplified model substrates. Based on these results a mechanistic rationale is proposed. This study involved multiple reactions and reactants, such as (2E,6E)-3,7-Dimethyl-8-oxoocta-2,6-dien-1-yl acetate (cas: 37905-02-5Formula: C12H18O3).
(2E,6E)-3,7-Dimethyl-8-oxoocta-2,6-dien-1-yl acetate (cas: 37905-02-5) belongs to esters. Esters perform as high-grade solvents for a broad array of plastics, plasticizers, resins, and lacquers, and are one of the largest classes of synthetic lubricants on the commercial market. Many esters have the potential for conformational isomerism, but they tend to adopt an s-cis (or Z) conformation rather than the s-trans (or E) alternative, due to a combination of hyperconjugation and dipole minimization effects. The preference for the Z conformation is influenced by the nature of the substituents and solvent, if present. Lactones with small rings are restricted to the s-trans (i.e. E) conformation due to their cyclic structure.Formula: C12H18O3
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics