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Title:Enzymic Oxidations of Ent-Kaurene and Ent-Kaurenol in Gibberellic Acid Biosynthesis: Stereochemistry and Isotope Effects
Author(s):Sherwin, Paul Frederick
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Organic
Abstract:The mixed function oxidase (MFO) catalyzed C19 hydroxylations of ent-kaur-16-ene (1) and of ent-kaur-16-en-19-ol (2) precede a complex cascade of enzyme catalyzed reactions leading to the plant growth regulator gibberellic acid. The stereochemistry and deuterium isotope effects (k(,H)/k(,D)) of these two oxidations were studied using stereospecifically labelled derivatives of 1 and 2 and microsomal enzyme extracts of Marah macrocarpus (wild cucumber) as the MFO source.
The intramolecular deuterium isotope effect of kaurene hydroxylation was determined to be 3.8 (+OR-) 0.6 by GC-MS analysis of the deuterated 2 produced in incubations of {19-('2)H(,2)}kaurene with M. macrocarpus microsomes.
The enzymic oxidation of 2 was found to proceed with stereospecific removal of the pro-R C19 hydrogen with an intermolecular deuterium isotope effect of 1.82 (+OR-) 0.02, through incubations of (19S)- and (19R)-{19-('3)H,('2)H}kaurenol. These were prepared by stereospecific borohydride reductions of {19-('3)H}kaurenal and {19-('2)H}kaurenal. The C19 isotopic configurations were assigned through chemical and NMR spectral correlations with synthetic decalin analogs of 2, for which the stereochemistry was established by a novel method involving stereospecific proton-phosphorus NMR coupling in a phosphorinane derivative.
Issue Date:1982
Description:288 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
Other Identifier(s):(UMI)AAI8302985
Date Available in IDEALS:2014-12-15
Date Deposited:1982

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