Total Synthesis of Cytochalasin B and

Cytochalasin B (1088) belongs to the [14]cytochalasan group and was isolated from Helminthosporium dematioideum (696) and Phoma S298 (695). Its first total synthesis was accomplished by Stork et al. in 1978 (740). Later, this group published a more simplified synthesis, utilizing an intramolecular Diels-Alder reaction as the key step, forming both perhydroisoindolone and the macrocyclic moiety in a single reaction (741). 

The starting material for this synthesis was iV,Ar-dibenzyl phenylalanal (1118), which is readily accessible from the corresponding amino acid (743). This was submitted to a Horner-Wadsworth-Emmons reaction with diethyl 3-oxo-2-butylphosphonate. The olefin obtained was then mono-iV-debenzylated, and then treated with t-butyldimethylsUyl triflate and 2,6-lutidine to give the sUyl enol ether 1119. Addition-elimination by treatment with methylene lactone 1120, synthesized earlier (744), provided Diels-Alder substrate 1121, which at high temperature 

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