Premium
Eine neue Synthese von (±)‐Pyrenophorin
Author(s) -
Gerlach Hans,
Oertle Konrad,
Thalmann Adolf
Publication year - 1977
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19770600838
Subject(s) - chemistry , acetal , silylation , reagent , ethylene , saponification , medicinal chemistry , yield (engineering) , organic chemistry , dehydrogenation , toluene , triphenylphosphine , catalysis , materials science , metallurgy
A new Synthesis of (±)‐Pyrenophorin The synthesis of pyrenophorin (I), a 16‐membered dilactone metabolite of plant pathogenic fungi is described. Reaction of the Grignard reagent II with the activated succinic acid ester III gave the methyl ( t ‐butyl)dimethylsilyloxy‐oxo‐octanoate IV which was converted into the corresponding ethylene acetal. Dehydrogenation via the benzeneselenenyl derivative lead to pyrenophorinic acid V with protected functional groups. Selective removal of silyl group followed by saponification of the ester group provided the ethylene acetal‐hydroxy acid VI suitable for the cyclodimerisation reaction. This was effected with azodicarbonic acid ester and triphenylphosphine at −40° in a dilute toluene solution. The 16‐membered dilactones VII with protected carbonyl groups were isolated in 24% yield. Silver‐ion induced cyclodimerisation of the S ‐2‐pyridyl carbothioate of VI gave much lower yields. Removal of the acetal groups lead to (±)‐pyrenophorin (I) and meso ‐pyrenophorin in about equal amounts.