1142120-31-7Relevant articles and documents
Total synthesis of vinblastine, vincristine, related natural products, and key structural analogues
Ishikawa, Hayato,Colby, David A.,Seto, Shigeki,Va, Porino,Tam, Annie,et al.
supporting information; experimental part, p. 4904 - 4916 (2009/09/30)
Full details of the development of a direct coupling of catharanthine with vindoline to provide vinblastine are described along with key mechanistic and labeling studies. Following an Fe(lll)-promoted coupling reaction initiated by generation of a presumed catharanthine radical cation that undergoes a subsequent oxidative fragmentation and diastereoselectivecoupling with vindoline, addition of the resulting reaction mixture to an Fe(III)-NaBHVair solution leads to oxidation of the C15'-C20' double bond and reduction of the intermediate iminium ion directly providing vi nblastine (40-43percent) and leurosidine (20-23percent), its naturally occurring C20' alcohol isomer. The yield of coupled products, which exclusively possess the natural C16' stereochemistry, approaches or exceeds 80percent and the combined yield of the isomeric C20' alcohols is >60percent. Preliminary studies of Fe(III)-NaBHVair oxidation reaction illustrate a generalizable trisubstituted olefin scope, identify alternatives toO 2 trap at the oxidized carbon, provide a unique entry into C20' functionalized vinblastines, and afford initial insights into the observed C20' diastereoselectivity. The first disclosure of the use of e xo-catharanthine proceeding through ?19'20'-anhydrovinblastine in such coupling reactions is also detailed with identical stereochemical consequences. Incorporating either a catharanthine Λ/-methyl group or a vindoline Λ/-formyl group precludes Fe(lll)-promoted coupling, whereas the removal of the potentially key C16 methoxy group ofvindoline does not adversely impact the coupling efficiency. Extension of these studies provided a total synthesis of vincristine (2) via &Lamb da;/-desmethylvinblastine (36, also a natural product), 16-desmethoxyvinblastine (44) and 4-desacetoxy-16- desmethoxyvinblastine (47) both of which we can now suggest are likely natural products produced by C. roseus, desacetylvin-blastine (62) and 4-desacetoxyvinblastine (59), as well as a series of key analogues bearing systematic modifications in the vindoline subunit. Their biological evaluation provided additional insights into the key functionality within the vindoline subunit contributing to the activity and sets the foundation on which further, more deep-seated changes in the structures of 1 and 2 will be explored in future studies.
