How many secondary carbocations are involved in the biosynthesis of avermitilol?

Organic Letters

Volumn 13, Issue 6, 2011, Pages 1294-1297

  Hong, Young J ^a   Tantillo, Dean J ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AVERMITILOL; CATION; SESQUITERPENE; WATER;

ARTICLE; CHEMICAL MODEL; CHEMICAL STRUCTURE; CHEMISTRY; CYCLIZATION; SYNTHESIS;

CATIONS; CYCLIZATION; MODELS, CHEMICAL; MOLECULAR STRUCTURE; SESQUITERPENES; WATER;

EID: 79952601835     PISSN: 15237060     EISSN: 15237052     Source Type: Journal    
DOI: 10.1021/ol103079v     Document Type: Article

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59. See the Supporting Information for a discussion of the alternative tertiary cation that could be formed by protonation of the C2=C3 π-bond of 3.
60. We also examined the potential of formate (a small model of an active site aspartate) as a hydrogen bond acceptor in this reaction. See the Supporting Information for details.
61. Unlike previous cases where two sequential secondary carbocations have been predicted to be avoided via triple-shift reactions, (4) only one of the putative secondary carbocations in the pathway to avermitilol is predicted to be avoided, perhaps due in part to the different nature of the events that lead to the formation and subsequent reaction of the first carbocation in this case-alkene protonation followed by cation-alkene cyclization, rather than an alkyl shift followed by a hydride shift as in the systems that participate in triple shifts.