Biosci. Biotechnol. Biochem., 71 (5), 1370–1371, 2007
Communication
An Efficient Conversion of Carboxylic Acids to One-Carbon Degraded
Aldehydes via 2-Hydroperoxy Acids
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Yoshihiko AKAKABE and Takeshi NYUUGAKU
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University,
1
677-1 Yoshida, Yamaguchi 753-8515, Japan
After the formation of dianions of a carboxylic acid
The process is illustrated in Scheme 1. In our initial
attempt, tetradecanoic acid (C ) was used as an even
carboxylic acid. Tetradecanoic acid was treated with
with lithium diisopropylamide, oxygen was bubbled into
the solution to produce 2-hydroperoxy acid. Then the
reaction mixture was acidified with a 2 N HCl solution
1
4
ꢁ
lithium diisopropylamide at ꢀ20 C to afford the dianion
ꢀ
and subsequently elevated to 50 C to afford the alde-
hyde with the loss of one carbon atom. Even saturated
formation. Then oxygen was bubbled into the dianion
ꢁ
solution at ꢀ78 C to produce 2-hydroperoxytetradeca-
7
)
(
C10–C20) and unsaturated (C18:1) carboxylic acids were
noic acid. The reaction was monitored as 9-anthryl-
5
)
converted into the odd aldehydes (C9–C19, C17:1) in high
yields. This conversion was found to be an efficient
method for the preparation of carboxylic acids (Cn) to
one-carbon degraded aldehydes (Cn-1) via 2-hydroper-
oxy acids.
diazomethane derivatives by HPLC. After purification
by medium-pressure column chromatography, 2-hydro-
peroxy acid was assigned by NMR. In order to in-
vestigate the condition of decarboxylation, the 2-hydro-
peroxy acid was treated with 2 N HCl aqueous solution.
ꢁ
When the temperature was raised to 50 C, the reaction
Key words: carboxylic acid; aldehyde; 2-hydroperoxy
acid; decarboxylation
was complete within 60 min. After standard treatment
and silica gel chromatography, tridecanal was obtained
quantitatively.
A variety of aldehydes occur in nature, and have
physiological functions. The aldehyde species have also
been used as valuable intermediates to synthesize target
compounds. For these reasons, various transformation
methods for aldehydes have been developed. The con-
version of alcohols to aldehydes by means of oxidants is
one of the most popular functional transformations in
organic synthesis. For example, aldehydes are prepared
from alcohols with PCC, Swern, Dess-Martin period-
According to essentially the same procedure, tri-
decanal was prepared by one-pot reaction. Thus, after
the formation of 2-hydroperoxytetradecanoic acid at
ꢁ
ꢀ78 C, the reaction mixture was acidified with 2 N HCl
ꢁ
solution and subsequently elevated to 50 C for 1 h to
afford tridecanal in high yield (85%).
In order to investigate the applicability of this method,
we selected a variety of even saturated carboxylic acids
(C10–C20). A series of carboxylic acids was converted
under the same reaction condition into odd aldehydes
(C –C ) with the loss of one carbon atom in high yields
1
–4)
inane, or TEMPO as oxidants.
Carboxylic acid esters
are also converted to aldehydes by means of DIBAH.
In spite of the availability of many reagents for these
transformations, there still exists a need for efficient and
convenient methods.
9
19
(83–88%). On the other hand, unsaturated carboxylic
acids (C18:1, n ¼ 9 (Z)- or (E)- form) were tested by this
procedure. The corresponding aldehydes (C17:1, n ¼ 9)
were obtained under the same condition at 70–76%
yield, and the stereochemistry of double bond did not
change in this reaction (no isomerization).
In summary, this conversion was found to be an
efficient method for the preparation of carboxylic acids
(Cn) to aldehydes (Cn-1) via the corresponding 2-
hydroperoxy acids. This new procedure is very simple
and cleanly affords the desired aldehydes at high yields.
In organisms, long-chain aldehydes (C15, C17) are
generated enzymatically from the corresponding fatty
5
,6)
acids (C16, C18) by ꢀ-oxygenase. In this process, fatty
acids (Cn) are converted into the corresponding 2-
hydroperoxy acids, followed by decarboxylation, to
afford aldehydes (Cn-1) with the loss of one carbon
atom. Hence we became interested in this enzymatic
process of even carboxylic acids to such odd aldehydes
via 2-hydroperoxy acids. Herein, we report an efficient
conversion of carboxylic acids to one-degraded alde-
hydes via 2-hydroperoxy acids.
Experimental
Representative experimental procedure. A solution
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