First synthesis of (1,2-13C2)-monolignol glucosides

Article abstract of DOI:10.1016/j.tetlet.2004.09.126

The monolignol glucosides (1,2-¹³C₂)-p-glucocoumaryl alcohol, (1,2-¹³C₂)-coniferin and (1,2-¹³C ₂)-syringin, and the glucosides of (1,2-¹³C ₂)-p-coumaric, (1,2-¹³C₂)-ferulic and (1,2-¹³C₂)-sinapic acids were synthesized by condensation of the corresponding aldehydes with (1,2,3-¹³C₃)-malonic acid. The free acids were converted to the acyl chlorides prior to their reduction to alcohols.

Full text of DOI:10.1016/j.tetlet.2004.09.126

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 8745–8747
First synthesis of (1,2-13C2)-monolignol glucosides
Vickram Beejmohun,a,b Eric Grand,a Franc¸ois Mesnard,b
b
Marc-Andre Fliniaux and Jose Kovensky
a,
*
´
´
a
´
´
Laboratoire des Glucides CNRS FRE 2779, Faculte des Sciences, Universite de Picardie ÔJules VerneÕ, 33 rue Saint-Leu,
80039 Amiens, France
b
´
´
Laboratoire de Phytotechnologie, Faculte de Pharmacie, Universite de Picardie ÔJules VerneÕ, 1 rue des Louvels, 80037 Amiens, France
Received 23 July2004; revised 15 September 2004; accepted 17 September 2004
Available online 5 October 2004
Abstract—The monolignol glucosides (1,2-13C2)-p-glucocoumaryl alcohol, (1,2-13C2)-coniferin and (1,2-13C2)-syringin, and the
glucosides of (1,2-13C2)-p-coumaric, (1,2-13C2)-ferulic and (1,2-13C2)-sinapic acids were synthesized by condensation of the corre-
sponding aldehydes with (1,2,3-13C3)-malonic acid. The free acids were converted to the acyl chlorides prior to their reduction to
alcohols.
Ó 2004 Elsevier Ltd. All rights reserved.
Lignans are widelydistributed plant metabolites associ-
ated with a range of biological activities. Podophylo-
toxin is used as an antiviral agent in the treatment of
genital warts1 and secoisolariciresinol diglucoside is a
natural cancer chemopreventive agent effective against
the onset of breast, prostate and colon cancers.2 The
biosynthetic pathway of lignans is not completely eluci-
dated, as it is specific to each species of plants.3 Most of
the present knowledge about the conversion of mono-
lignols to their dimers lignans and the formation of cell
wall lignins in plants comes from incorporation experi-
ments using specificallylabelled precursors or
substrates.4,5
Onlyone synthesis of (1,2- 13C2) coniferyl alcohol has
8
been previouslyreported.
Therefore, we decided to
prepare the three monolignol glucosides, that should
be easilyincorporated byplant cells. Glucosides of
monolignols are involved in the supplyof monolignols
before polymerization.9 Moreover, the carbohydrate
moietyshould make the substrate less toxic for in vitro
cultured cells.
In this letter, we report on the synthesis of the labelled
monolignol glucosides (1,2-13C2)-p-glucocoumaryl alco-
hol, (1,2-13C2)-coniferin and (1,2-13C2)-syringin and
their precursors, the glucosides of (1,2-13C2)-p-coumaric,
(1,2-13C2)-ferulic and (1,2-13C2)-sinapic acids.
Monolignol glucosides (p-glucocoumaryl alcohol, conif-
erin, syringin) are considered to be the storage or excre-
tion form of monolignols.6 The synthesis of monolignol
glucosides enriched with 13C at specific positions has
been used to prove their effective incorporation in lig-
nin.7 However, to obtain detailed information about
the biosynthetic route of lignans in vivo, the synthesis
of multiple labelled precursors becomes necessary. The
presence of two consecutive 13C atoms in monolignol
molecules allows to follow their conversion to dimers
due to the characteristic signals observed in the NMR
spectra of intermediates involved.
The synthetic strategy follows in part the previously de-
scribed preparation of unlabelled compounds10–13 and is
shown in Scheme 1. Conversion of p-hydroxybenzalde-
hyde (1a), vanillin (1b) and syringaldehyde (1c) to their
corresponding b-glucosides was performed with tetra-O-
acetyl-a-D-glucopyranosyl bromide and silver oxide in
quinoline to give 2a, 2b and 2c in 65%, 73% and 75%
yields, respectively. The b-configuration of the glycosi-
dic bond was confirmed byNMR ( J1 ,2 = 7.8Hz). Fur-
ther attempts to substitute the high boiling point
solvent by pyridine or triethylamine–CaCO3 were
unsatisfactory.
0
0
The introduction of the double 13C labelling was accom-
plished bycondensation of 2a–c with readilyavailable
(1,2,3-13C3)-malonic acid leading, after decarboxylation,
Keywords: Monolignols; Synthesis; Isotopic labelling; Carbon 13.
*
Corresponding author. Tel.: +33 3 22 82 75 67; fax: +33 3 22 82 75
68; e-mail: jose.kovensky@u-picardie.fr
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.09.126

8746
V. Beejmohun et al. / Tetrahedron Letters 45 (2004) 8745–8747
O
OH
1
*
H
O
CHO
*
2
3
1'
2'
3'
6'
ii
i
AcO
R1
R2
R1
R2
AcO
R15'
R2
O
4'
O
O
6"
5"
OH
O
4"
1"
AcO
AcO
OAc
AcO
AcO
2"
OAc
3"
1a-c
2a-c
3a-c
R1 R2
a H
b H
H
OMe
iv, v, vi
iii
c OMe OMe
OH
OH
OH
O
*
*
*
*
*
*
HO
HO
R1
O
R1
O
HO
R1
O
R2
R2
R2
O
O
O
HO
HO
HO
HO
HO
HO
OH
OH
OH
5a-c
5'a-c
4a-c
Scheme 1. Reagents and conditions: (i) tetra-O-acetyl-a-D-glucopyranosyl bromide, Ag2O, quinoline, rt, 2h; (ii) 13CH2(13COOH)2, pyridine,
piperidine, 1h at 55°C and 2h at 85°C; (iii) MeONa, MeOH, rt, overnight; (iv) (COCl)2, CH2Cl2, rt, overnight; (v) NaBH4, THF, rt, 4h; (vi) NH3,
MeOH, rt, overnight.
to compounds 3a–c in 70% yield. The typical pattern
of consecutive labelling was observed in the 13C NMR
spectra. For example, in the spectrum of compound 3b
in CDCl3 the two doublets appear at d 171.3 (C-1)
and d 116.1 (C-2) with a J1,2 = 74Hz.
alcohol 5b and about 30–50% of a product resulting
from the reduction of the 2,3-double bond (compound
50b). Changes in reagent and/or substrate concentration,
solvent and temperature were unsuccessful to increase
the 5b/50b ratio and gave no reproductible yields.
Since the free acids are also interesting substrates for
biosynthetic studies, the deprotection of the sugar moi-
etywas performed in MeONa–methanol. After purifica-
tion byflash chromatographyon silica gel the acids 4a,
4b and 4c were obtained as white solids.14
Therefore, we decided to change to the acyl chloride
route. The reaction of 3b with oxalyl chloride at room
temperature gave the corresponding acyl chloride. Par-
tial degradation was observed when the acyl chloride
was prepared with thionyl chloride instead of oxalyl
chloride.
The synthesis of the labelled monolignols from the cor-
responding protected acids 3a–c can be performed by
two different routes: through esters or acyl chlorides
derivatives. Both were explored using 3b as model com-
pound. First, the methyl ester was prepared using
KHCO3–MeI–TBAI in excellent yields (93–97%). Dif-
ferent reducing conditions were tested. LiAlH4–AlCl3
lead to low yields of the reduction product accompanied
The reduction of the acyl chloride with NaBH4 is
affected bythe solvent employed. In diethyl ether, the
reaction did not go to completion, while the use of
THF at room temperature lead smoothly, after deacetyl-
ation, to the desired alcohol 5b, keeping the level of the
reduced double bond by-product 50b around 5%.
bydegradation by-products. On the other hand, LiBH
Therefore, the sequence acid–acyl chloride–reduction–
deacetylation was applied to the three precursors 3a,
3b and 3c, leading to the expected alcohols 5a,b and
5c, in 60%, 68% and 70% yields, respectively. The 13C
NMR spectra of the final products15 showed the expected
two doublets at d 130.05 and 61.56 (J1,2 = 47Hz).
4
at 60°C or LiAlH4 at room temperature allowed to
accomplish the reduction of the carboxyl group in 63%
and 90% yields, respectively. However, after deacetyl-
ation, NMR and mass spectra showed that the isolated
product was in fact a mixture of the expected allylic

V. Beejmohun et al. / Tetrahedron Letters 45 (2004) 8745–8747
8747
In summary, the monolignol glucosides (1,2-13C2)-p-
glucocoumaryl alcohol, (1,2-13C2)-coniferin and
(1,2-13C2)-syringin and their acid precursors have been
prepared for the first time.
7. Terashima, N.; Seguchi, Y.; Robert, D. Holzforschung
1991, 45, 35–39.
8. Newman, J.; Rej, R. N.; Just, G.; Lewis, N. G. Holzfors-
chung 1986, 40, 369–373.
9. Matsui, N.; Fukushima, K.; Yasuda, S.; Terashima, N.
Holzforschung 1996, 50, 408–412.
10. Fuchs, W. Chem. Ber. 1955, 88, 1825–1827.
11. Kratzl, K.; Billek, G. Monatsh. Chem. 1953, 84, 406–414.
12. Kratzl, K.; Billek, G. Holzforschung 1953, 7, 66–70.
13. Terashima, N.; Ralph, S. A.; Landucci, L. L. Holzfors-
chung 1996, 50, 151–155.
Acknowledgements
This work was carried out with the financial contribu-
´
tion of the Conseil Regional de Picardie (Pole IBFBio).
V.B. thanks the Conseil Regional de Picardie for a
ˆ
14. All new compounds were characterized byspectroscopical
methods. Analytical data for compound 4c: mp 253–
254°C; [a]D ꢀ13 (c 0.04, CH3OH); 1H NMR (300MHz,
´
fellowship. We thank Serge Pilard of the Plateforme
´
Analytique of the Universite de Picardie ÔJules VerneÕ
for mass spectrometryexperiments.
CD3OD): d 7.35 (ddd, 1H, J2,3 = 15.9, J3, C-1 = 6.0, J3, C-2
=
2.5Hz, H-3), 6.88 (s, 2H, H-20, H-60), 6.48 (ddd, 1H,
J2, C-1 = 2.7, J2, C-2 = 155.6Hz, H-2), 4.93 (d, 1H,
00
00 00
J1 ,2 = 7.3Hz, H-1 ), 3.88 (s, 6H, 2CH3O–), 3.79 (dd,
00 00
1H, J5 ,6 a = 2.5, J6 a,6 b = 12.0Hz, H-600a), 3.68 (dd, 1H,
00 00
References and notes
00
00
J5 ,6 b = 4.9Hz, H-600b), 3.50–3.40 (m, 3H, H-200, H-300, H-
00 00
1. Beutner, K. R.; von Krogh, G. Semin. Dermatol. 1990, 9,
148–151.
400), 3.23 (ddd, 1H, J4 ,5 = 7.3Hz, H-500). 13C NMR d
175.33 (d, J1,2 = 67Hz, C-1), 126.06 (d, C-2). ESMS
12
2. Thompson, L. U.; Seidl, M. M.; Rickard, S. E.; Orcheson,
L. J.; Fong, H. H. S. Nutr. Cancer 1996, 26, 159–165.
3. Croteau, R.; Kutchan, T. M.; Lewis, N. G. In Biochem-
istry and Molecular Biology of Plants; Buchanan, B.,
Gruissem, R., Jones, P., Eds.; American Societyof Plant
Physiologists, 2000; pp 1250–1302.
4. Seidel, V.; Windho¨vel, J.; Eaton, G.; Alfermann, A. W.;
Arroo, R. R. J.; Medarde, M.; Petersen, M.; Woolley, J.
G. Planta 2002, 215, 1031–1039.
5. Ford, J. D.; Huang, K.-S.; Wang, H.-B.; Davin, L. B.;
Lewis, N. G. J. Nat. Prod. 2001, 64, 1388–1397.
6. Gross, C. G. In Biosynthesis and Biodegradation of Wood
Components; Higuchi, T., Ed.; Academic Press:
New York, 1985; pp 229–271.
(+Na): Calcd for
Found: 411.1189.
C
13C2H22O10Na: m/z 411.1178.
15
15. Analytical data for compound 5c: syrup; [a]D ꢀ2 (c 0.07,
CH3OH); 1H NMR (300MHz, CD3OD): d 6.75 (s, 2H,
H-20, H-60), 6.55 (ddd, 1H, J2,3 = 16.0, J3, C-1 = 6.0Hz,
J3, C-2 = 3.0Hz, H-3), 6.11 (dddt, 1H, J1,2 = 4.0, J2, C-1
00 00
=
2.5, J2, C-2 = 154.0Hz, H-2), 4.90 (d, 1H, J1 ,2 =7.3Hz, H-
100), 4.22 (br dt, 2H, J1, C-1 = 142.0, J1,2 = J1, C-2 = 4.3Hz,
00 00
H-1), 3.83 (s, 6H, 2CH3O–), 3.78 (dd, 1H, J5 ,6 a = 2.5,
00
J6 a,6 b = 12.0Hz, H-600a), 3.68 (dd, 1H, J5 ,6 b = 5.1Hz,
00
00 00
H-600b), 3.45–3.35 (m, 3H, H-200, H-300, H-400), 3.20 (m, 1H,
H-500). 13C NMR d 130.05 (d, J1,2 = 47Hz, C-2), 61.56 (d,
13C2H24O9Na: m/z
12
C
C-1). ESMS (+Na): Calcd for
397.1385. Found: 397.1394.
15