Terpenes biogenetic rearrangements

Coates, R. M. Biogenetic-Type Rearrangements of Terpene. In Progress in the Chemistry of Organic Natural Products, Vol. 33 (Herz, W., H. Grisebach, and G. W. Kirby, eds.), p. 73. Wien-New York Springer. 1976. 

Coates, R. M., Biogenetic-type rearrangements of terpenes, Fortschr. Chem. Org. Naturst., 33, 73-220 (1976). 

The skeleton of the sesquiterpenes thapsene 140 and 141 contains three contiguous quaternary centers [33]. The synthesis of two biogenetical precursors of these terpenes started with cyclogeraniol 143. Orthoester rearrangement afforded ester 144. As in several other syntheses, the third quaternary center resulted from diazoketone cyclopropane insertion affording in this synthesis compound 146 (Scheme 6.21). 

Contents L. MINALE, G. CIMINO, S. DE STEFANO, and G. SODANO, Natural Products from Porifera - R. M. COATES, Biogenetic-Type Rearrangements of Terpenes - K. L RINEHART, JR., and L. S. SHIELD, Chemistry of the Ansamycin Antibiotics - A. FONTANA and C. TONIOLO, The Chemistry of Tryptophan in Peptides and Proteins -P. HEMMERICH, The Present Status of Flavin and Flavocoenzyme Chemistry - Author Index - Subject Index. 

It has been possible to effect the reverse rearrangement, i.e., the conversion of artemisyl derivations to chrysanthemane and/or santolinane products 71, 72), as shown below. These homoallyl homoallyl rearrangements no doubt proceed through a cyclopropylcarbinyl (chrysan-themyl) intermediate e.g., (29->28->31)]. The realization of these transformations has led to an alternative proposal that the biogenetic precursor to these irregular terpenes is actually an artemisyl derivative. 

Biogenetic-Type Rearrangements of Terpenes SbFs, SOgClF... 

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