Über eine Synthese des all‐trans‐1.1.10.10‐Tetracarbäthoxy‐3.8‐dimethyl‐decatriens‐(3.5.7) und des all‐trans‐4.9‐Dimethyl‐dodecapentaen‐(2.4.6.8.10)‐disäure‐(1.12)‐dimethylesters

Abstract

5.7) entsteht durch Kondensation von 2 Moll. Na-Malonsaurediathylester mit all-trans-l.8-Dibrom-2.7-dimethyl-octatrien-(2.4.6), das aus dem Clo-Triendiester I a uber das Diol I bl zuganglich ist. -Eine WIrrrc-Reaktion zwischen all-trans-2.7-Dimethyl-octatrien-(2.4.6)-dial-(1.8) und 2 Moll. Carbomethoxymethylen-triphenylphosphoran fiihrt in 72-proz. Ausbeute zum all-trans-4.9-Dimethyl-dodecapentaen-(2.4.6.8. IO)-disiiure-(l. 12)-dimethylester.

A Short and Efficient Synthesis of Crocetin-dimethylester and Crocetindial

“…The traditional synthetic approaches for compounds 1 − 4 involve the bismetal acetylide coupling/partial hydrogenation 1,6 or the Wittig and related reactions. , However, these procedures invariably produce a mixture of isomers, requiring careful, tedious, and unproductive isolation−purification processes. ,2c The highly efficient Julia's sulfone olefination protocol has found wide use in the preparation of simple double bonds and conjugated polyenes, but the presumed instability of some intermediates has limited the general utilization of this method …”

Total Synthesis of Bioactive Marine Macrolides

“…Oxidation of the commercially available ribofuranoside 305 to the CIO aldehyde115 was followed by Wittig olefination. Methoxide-catalyzed transesterification of 311 and hydroxyl deprotection led to partial epimerization to the desired C12 epimer 312 (2:l mixture of 312 and 313). The configuration at C11 needed to be inverted, and this was accomplished by conversion to the cyclic sulfate and regioselective nucleophilic substitution117 at C11 to provide 307.…”

Diallylic Sulfides as Key Structures for Carotenoid Syntheses

“…Two representative synthetic approaches for the polyene chain of carotenoids are Wittig olefination and the bismetal acetylide coupling/partial hydrogenation . Even though the highly efficient Julia's sulfone olefination protocol has found wide use in the preparation of simple double bonds and conjugated polyenes, there has been no report of carotenoid syntheses based on this method, as generalized in Scheme , because of the presumed instability of dihalotriene 3 . To circumvent the instability problem of 3 , we decided to use diallylic sulfide 6b , where the sulfur atom isolated the two allylic halide units, thus providing stability to the system.…”