1
904
C. Crestini et al. / Bioorg. Med. Chem. 7 (1999) 1897±1905
products were performed using a DB1 column (30 m
Â0.25 mm and 0.25 mm ®lm thickness), and an iso-
out in buer citrate phosphate 100 mM pH 3 or 6 at
ꢀ
50 C. To a suspension of lignin (60 mg/30 mL) was
ꢀ
followed by a 20 C/min temperature gradient to 300 C
thermal temperature pro®le of 100 C for the ®rst 2 min,
added the porphyrin (10 mg/30 mL) under stirring. The
addition of hydrogen peroxide (30%, 20 mL) initiated
the reaction. Hydrogen peroxide was further supplied
every 20 min to a ®nal amount of 100 mL. After 6 h the
reaction mixture was centrifuged, washed thoroughly
with water, centrifuged again and freeze-dried.
ꢀ
and ®nally an isothermal period at 300 C for 10 min.
ꢀ
ꢀ
The injector temperature was 280 C. Chromatography
ꢀ
grade helium was used as the carrier gas. The fragmen-
tation patterns are shown in Table 3. In order to fully
characterize the recovered products, some of the reac-
tions were performed using 0.1 mmol of substrates 1 and
Quantitative 31P NMR. Derivatization of the lignin
samples with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxa-
phospholane were performed as previously described.
Samples of lignin, (30 mg) accurately weighed, were
dissolved in a solvent mixture composed of pyridine and
deuterated chloroform, 1.6/1 v/v ratio (0.5 mL). The
phospholane (100 mL) was then added, followed by the
internal standard and the relaxation reagent solution
(100 mL each).
5
hexane/ethyl acetate as eluant mixture and character-
. The oxidation products were isolated by TLC using
1
ized by H NMR spectroscopy.
2
1
-Methoxy-5-methyl-3(2,3-dimethoxy-5-methylphenyl)-
1
,4-benzoquinone 2. H NMR (CDCl ) (2.33 (s, 3H,
3
CH ), 2.33 (d, J=1 Hz, 3H, CH ) 3.64 (s, 3H, OCH ),
3
3
3
3.84 (s, 3H, OCH ), 3.88 (s, 3H, OCH ), 6.65 (s, 1H,
CH), 6.74 (s, 1H, CH), 6.74 (q J=1 Hz, 1H, CH).
3 3
Acknowledgements
2
phenyl)1,4-benzoquinone 3. H NMR (CDCl ) (2.33 (s,
-Methoxy-5-hydroxymethyl-3(2,3-dimethoxy-5-methyl-
1
3
The authors wish to thank Dr. D. S. Argyropoulos for
the insightful suggestions and discussions. We also
thank Mr. Alessandro Leoni for his valuable technical
support. Italian M.U.R.S.T. and C.N.R. are acknowl-
edged for ®nancial support.
3H, CH ), 3.64 (s, 3H, OCH ), 3.84 (s, 3H, OCH ), 3.88
3 3 3
(
s, 3H, OCH ), 4.56 (d, J=1 Hz, 2H, CH OH), 6.65 (s,
3 2
1H, CH), 6.74 (s, 1H, CH), 6.74 (t, J=1 Hz, 1H, CH).
3,4-Dimethoxy-5(2,3-dimethoxy-5-methylphenyl)benzyl
alcohol 4. H NMR (CDCl ) (2.33 (s, 3H, CH ), 3.64
1
3
3
(
4
s, 3H, OCH ), 3.83 (s, 6H, OCH ), 3.88 (s, 3H, OCH ),
3 3 3
.56 (d, J=1 Hz, 2H, CH OH), 6.6±6.9 (m, 4H, CH).
2
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2
Oxidation of residual kraft residual lignin. General pro-
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