Vincadifformine total synthesis

In Kuehne s total synthesis of vincadifformine (89), the pentacyclic natural product was obtained when tetracyclic phenylselenide 88 was treated with 2.5 equivalents of n-Bu SnH and the radical initiator AIBN in refluxing benzene [52]. The stereochemistry of the phenylselenyl substituent in the tetracyclic precursor had no impact on the product yield. After the tertiary radical intermediate 90 was generated (Scheme 17), the 5-exo-trig cyclization was prohibited... 

Another impressive contribution to synthesis in this area is the total synthesis of vincadifformine (211) and ervinceine (212) (=ll-methoxyvincadifformine) by... 

The use of 2-vinylindole species has played a large role in the total synthesis of the pentacyclic Aspidosperma alkaloids. In 1978, Kuehne reported an elegant synthesis of DL-vincadifformine (182) that featured as a key step the reaction of an indoloa-zepine 177 with the bromoaldehyde 178, thus leading to the in situ formation of 2-vinylindole species 181, which in turn underwent an intramolecular Diels-Alder reaction to provide 182 [71] (Scheme 42). Kuehne and others have used this same methodology, using the in situ generation of a 2-vinyl indole, followed by an intramolecular Diels-Alder reaction, to synthesize a number of Aspidosperma alkaloids and their analogs [72]. 

Fuknyama and colleagnes employed this indole ring synthesis in total syntheses of ( )-vincadifformine [11], (-)-tabersonine [11], (-)-vindoline [13], (-)-aspidophytine [15, 16], and tryprostatins A and B [17]. For reviews of isocyanide-based indole synthesis and organic synthesis using isocyanides in general, see Campo and colleagnes and Tobisu and colleagues [19,20],... 

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