May 1998
SYNLETT
475
A New Efficient Access to Glycono-1,4-lactones by Oxidation of Unprotected Itols by
Catalytic Hydrogen Transfer with RhH(PPh ) -Benzalacetone System
3 4
I. Isaac, G. Aizel, I. Stasik, A. Wadouachi, D. Beaupère*
Université de Picardie Jules Verne-Laboratoire de Chimie Organique, 33 rue St Leu-80039 Amiens Cédex, France
Received 29 December 1997
Abstract: Treatment of unprotected pentitols and hexitols with
RhH(PPh ) -benzalacetone system leads exclusively to glycono-1,4-
3 4
lactones in 60-96% yield.
The literature records a number of methods for the conversion of diols
to lactones in yields varying from good to poor. These include: silver
1
2
carbonate on Celite, stoichiometric RuCl (PPh ) in benzene, CuSO -
2
3 3
4
3
KMnO , tetrapropylammonium perruthenate-4-methylmorpholine N-
oxide, and catalytic hydrogen transfer (C.H.T) [benzalacetophenone-
RuH (PPh ) ] at 140°C. To our knowledge, the latter is the only
4
4
5
2
3 4
method which has been described to oxidize protected pentitols to
6
afford the corresponding pentonolactones and no method was
applicable for the oxidation of unprotected itols to glyconolactones.
In a previous paper we described the oxidation of protected or
unprotected lactols to glycono-1,4-lactones, in mild conditions, by
C.H.T
with
benzalacetone
as
hydrogen
acceptor
and
7
RhH(PPh ) (hydridotetrakis triphenylphosphine rhodium I) as catalyst.
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We report here the use of this system for the oxidation of unprotected
itols to prepare glycono-1,4-lactones.
As a matter of fact, we observed that treatment of meso erythritol 1 with
RhH(PPh ) (0.2 eq) and benzalacetone (4 eq) in DMF for 3 hours at
3 4
60°C led to the racemic mixture of D,L-erythrono-1,4-lactone 2 in 95%
isolated yield (Scheme 1). This method was also applied to other
unprotected itols (tetritols, pentitols and hexitols) and efficiently yielded
the glycono-1,4-lactones as shown in the Table.
Scheme 1
Pentitols and hexitols which have a plane of symmetry, for example
meso erythritol 1, D-xylitol 8, D-galactitol 18 or a C-2 symmetry axis,
such as D-threitol 3 or D-mannitol 13 led, with good yields, to the
corresponding lactone obtained in a racemic mixture.
Only one exception was observed when D-ribitol 5, having a plane of
symmetry, was oxidized with 0.2 eq of catalyst and 4 eq of
benzalacetone at 60°C for 5 hours. D,L-Ribono-1,4-lactone 6 and D,L-
The oxidation of L-arabinitol which has no symmetry led to the two
expected L-arabinono-1,4-lactone 11 and L-lyxono-1,4-lactone 12 in
72% overall yield and in ratio 11/12=1.25:1.
arabinono-1,4-lactones
7 were isolated in 47% and 18% yield
respectively. Similar epimerisation at C-2 was already observed in the
oxidation of 2-acetamido-2-deoxy-D-mannopyranose with the same
As explained in Scheme 2, after an oxidation at C-1 of L-arabinitol, the
L-arabinopyranose or furanose formed was oxidized to give the L-
arabinono-1,4-lactone 11. The rare L-lyxono-1,4-lactone 12 is obtained
via the L-lyxose resulting from the oxidation at the C-5 of the starting
itol.
8
oxidizing system.
When the oxidation of D-ribitol was performed at 80°C with 0.4 eq of
RhH(PPh ) the overall yield increased to 94% but the ratio 6/7
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remained equal to 2.5:1.