Precursors to damascenone: synthesis and hydrolysis of isomeric 3,9-dihydroxymegastigma-4,6,7-trienes.
A series of four isomeric 3,9-dihydroxymegastigma-4,6,7-trienes, 8, has been prepared. The (3S,6R,9S) isomer of 8 proved to be identical to an isomer of this compound tentatively identified as an intermediate in the formation of damascenone from an allene triol. Each of the four isomers, when hydrolyzed independently of each other at pH 3.0 and 25 degrees C, produced product mixtures in which the major product was damascenone (1). Contrary to expectation, 3-hydroxydamascone (5) was not observed in any of the hydrolyses. Consequently, the mechanism of formation of damascenone proposed earlier requires modification. In each hydrolysis, the product mixtures showed the presence of a second isomer of 8, produced by epimerization during hydrolysis. Chiral analysis on a Cyclosil B column revealed that this epimerization was occurring at C(3) in each of the hydrolyses.
Puglisi
Carolyn J
CJ
The Australian Wine Research Institute, P.O. Box 197, Glen Osmond, South Australia 5064, Australia.
Daniel
Merran A
MA
Capone
Dimitra L
DL
Elsey
Gordon M
GM
Prager
Rolf H
RH
Sefton
Mark A
MA
D000466:Alkadienes / Q000737:chemistry; D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D003510:Cyclohexanes / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007536:Isomerism; D010938:Plant Oils / Q000737:chemistry; D027826:Rosa / Q000737:chemistry*
D000466:Alkadienes; D000475:Alkenes; D003510:Cyclohexanes; D010938:Plant Oils; C502869:damascenone; C025947:propadiene