Some studies into the synthesis of furaneol
The purpose of this research was to develop simple routes for furanones
from readily available carbohydrate sources.
Of particular interest was the synthesis of 4-hydroxy-2,5-dimethyl-
3(2H)-furanone, more commonly known as furaneol, a widely occurring
The preparation of furaneol has been the subject of considerable study in
recent years in view of possible applications as a flavouring agent in
Our primary approach to the synthesis of furaneol uses as a final step,
the known cyclization of 3,4-dihydroxyhexane-2,5-dione to furaneol under
basic conditions, and the present research for the most part is concerned
with the development of an alternative synthesis of the dione.
A suitably cheap and readily available starting material for such a
synthesis appeared to be L-(+)-tartaric acid. In this case the
required synthetic transformation involves the conversion of the two
carboxyl groups of the acid into acetyl functions.
An extensive investigation was undertaken into the preparation of
suitable L-(+)-tartaric acid derivatives and their reaction with
organometallic reagents, principally Grignard reagents, in order to
accomplish the required conversion.
(R, R)-4,5-dicyano-2,2-dimethyl-1,3-dioxolan (2,3-0-isopropylidene-Ltartaronitrile)
and (4R, 5R)-(+)-2,2, N, N, N', N'-hexamethyl-l, 3-
dioxolan-4,5-dicarboxyamide, (2,3-0-isopropylidene-N, N, N', N'-
tetramethyl-L-tartramide), were found to react with Grignard reagents
to afford 2,3-dihydroxy-l, 4-diones in which the hydroxyl groups at the 2,
and 3 positions are protected as isopropylidene acetals.
Treatment of (4R, 5R)-4,5-diacetyl-2,2 =dimethyl-1,3-dioxolan, (3,4-0-
isopropylidene (3R, 4R)-3,4-dihydroxyhexane-2,5-dione, prepared by either
of the above procedures, with trifluoroacetic acid-water (9: 1 v/v) gave a
crude sample of (3R, 4R)-3,4-dihydroxyhexane-2,5-dione, which on reaction
with aqueous piperidinium acetate afforded furaneol.
The overall yield of furaneol obtained in this way from L-(+)-tartaric
acid was 19%.
An alternative approach to the synthesis of furaneol which was
investigated briefly, involved the preparation of 1-deoxy-D-fructose
by a literature procedure. Treatment of 1-deoxy-D-fructose with piperidinium
acetate in absolute ethanol however, failed to give either furaneol or