C. Vogel et al., GALACTURONIC ACID-DERIVATIVES .9. REGIOSELECTIVE ENZYMATIC ACETYL ESTER HYDROLYSIS OF D-GALACTURONIC ACID-DERIVATIVES AND RELATED REACTIONS, Liebigs Annalen, (7), 1997, pp. 1425-1428
A number of D-galacturonic acid derivatives (1, 3, 7 and 9) have been
selectively deacetylated in enzyme-catalyzed reactions. The 2-O-acetyl
groups were selectively hydrolyzed from -tri-O-acetyl-beta-D-galactop
yranurono-6,1-lactone (1), and methyl [methyl (3) and benzyl (7) 3,4-t
ri-O-acetyl-beta-D-galactopyranosid]uronates, affording the specifical
ly deacetylated products in good to excellent yields. The methyl 1,2,3
,4-tetra-O-acetyl-alpha-D-galactopyranuronate (9) was hydrolyzed at th
e anomeric position in 48% yield using the acylase from Aspergillus me
lleus (E-1), whereas the lipases from wheat germ (E-5 and E-7) catalyz
ed the selective cleavage of the acetyl groups in both the 1- and 2-O-
positions, furnishing the methyl 3,4-di-O-acetyl-D-galactopyranuronate
(12) in 46% isolated yield. The latter compound was obtained in nearl
y quantitative yield by selective enzymatic deacetylation at the 2-O-p
osition of 7, followed by hydrogenolytic cleavage of the anomeric O-be
nzyl group. Isopropylidenation of 12 furnished the hitherto unknown me
thyl l-1,2-O-isopropylidene-alpha-D-galactopyranuronate (13).