Spongian pentacyclic diterpenes. Stereoselective synthesis of (-)-dendrillol-1
摘要:
A formal total synthesis of the spongian diterpene (-)-dendrillol-1 (3), through a consice approach that could be used for the synthesis of other pentacyclic spongian diterpenes, is reported. The synthesis is based on the intramolecular acetalization of an acid-dialdehyde 4, which is prepared from (+)-podocarp-8(14)-en-13-one (5) via a sequence of transformations involving (a) introduction of a latent dialdehyde unit on 5 by photochemical reaction with acetylene, (b) reductive carboxylation at C-13 of photoadduct 6 to obtain acid 18, and (c) elaboration of the dialdehyde moiety at C-8 and C-14 of 18 by ozonolysis. Several procedures that have been examined for the reductive carboxylation at C-13 of 6 are described. A simple three-step procedure to effect the conversion of a podocarp-8-en-13-one system into a C-17-functionalized beyerane compound is also reported.
Spongian pentacyclic diterpenes. Stereoselective synthesis of (-)-dendrillol-1
摘要:
A formal total synthesis of the spongian diterpene (-)-dendrillol-1 (3), through a consice approach that could be used for the synthesis of other pentacyclic spongian diterpenes, is reported. The synthesis is based on the intramolecular acetalization of an acid-dialdehyde 4, which is prepared from (+)-podocarp-8(14)-en-13-one (5) via a sequence of transformations involving (a) introduction of a latent dialdehyde unit on 5 by photochemical reaction with acetylene, (b) reductive carboxylation at C-13 of photoadduct 6 to obtain acid 18, and (c) elaboration of the dialdehyde moiety at C-8 and C-14 of 18 by ozonolysis. Several procedures that have been examined for the reductive carboxylation at C-13 of 6 are described. A simple three-step procedure to effect the conversion of a podocarp-8-en-13-one system into a C-17-functionalized beyerane compound is also reported.
In this article, a novel methodology for the study of complex reaction mechanisms is explored, and applied to the kinetic analysis of the hydrolysis reactions of ciclohexanecarbonitriles. The kinetic data were first analyzed with the help of classic linear techniques. Subsequently, the determination of the rate constants by a non-linear, least-squares (LS) fitting method, followed by a novel eigenvalue-eigenvector analysis of the sensitivity coefficients, permitted us to obtain the maximum possible information from the kinetic data. The non-linear, LS-fitting method, carried out by means of a new version of OPKINE program, allowed the calculation of all the rate constants of the mechanism; in addition, the sensitivity analysis permitted us to establish the uniqueness and reliability of calculated rate coefficients. Finally, the results of the sensitivity analysis were tested by means of a simulation procedure, and the results compared to those obtained from classic linear methods. (C) 1999 John Wiley G Sons, Inc. Int I Chem Kinet 31: 611-626, 1999.
Spongian pentacyclic diterpenes. Stereoselective synthesis of (-)-dendrillol-1
作者:Antonio Abad、Manuel Arno、Ana C. Cunat、M. Luisa Marin、Ramon J. Zaragoza
DOI:10.1021/jo00051a035
日期:1992.12
A formal total synthesis of the spongian diterpene (-)-dendrillol-1 (3), through a consice approach that could be used for the synthesis of other pentacyclic spongian diterpenes, is reported. The synthesis is based on the intramolecular acetalization of an acid-dialdehyde 4, which is prepared from (+)-podocarp-8(14)-en-13-one (5) via a sequence of transformations involving (a) introduction of a latent dialdehyde unit on 5 by photochemical reaction with acetylene, (b) reductive carboxylation at C-13 of photoadduct 6 to obtain acid 18, and (c) elaboration of the dialdehyde moiety at C-8 and C-14 of 18 by ozonolysis. Several procedures that have been examined for the reductive carboxylation at C-13 of 6 are described. A simple three-step procedure to effect the conversion of a podocarp-8-en-13-one system into a C-17-functionalized beyerane compound is also reported.