Exploitation of sugar ring flipping for a hinge-type tether assisting a [2 + 2] cycloaddition

Article abstract of DOI:10.1039/b609115f

Methyl 3-O-p-methoxybenzyl-β-d-xylopyranoside (2) was exploited as a novel hinge-type tether for the [2 + 2] cycloaddition of cinnamate. The major ring conformation occupied by the 2,4-dicinnamate derivative of 2 was ⁴C₁, which exten

Full text of DOI:10.1039/b609115f

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Exploitation of sugar ring flipping for a hinge-type tether assisting a [2 + 2]
cycloaddition†
Hideya Yuasa,* Masatoshi Nakatani and Hironobu Hashimoto
Received 27th June 2006, Accepted 11th August 2006
First published as an Advance Article on the web 30th August 2006
DOI: 10.1039/b609115f
Methyl 3-O-p-methoxybenzyl-b-D-xylopyranoside (2) was exploited as a novel hinge-type tether for the
[2 + 2] cycloaddition of cinnamate. The major ring conformation occupied by the 2,4-dicinnamate
derivative of 2 was 4C1, which extends two cinnamates along a diequatorial orientation. However,
3-O-deprotected dicinnamate 5, when in a non-polar solvent, favours the 1C4 conformation, which
assists the approach of two cinnamates with the 1,3-diaxial scaffold. Photoirradiation of compound 5 at
313 nm in CHCl3 afforded the intramolecular cycloaddition of cinnamates to give methyl b-, d-, and
n-truxinates in a 86 : 8 : 6 ratio after transesterification with methanol. The regio- and stereoselectivities
are comparable to those reported by others for tethered cinnamates. The per-deuterated dicinnamate
derivative of 5 facilitated the conformation analyses of the pyranoside rings by 1H NMR, indicating
that all the products of photoirradiation had 1C4-fixed pyranosides. Excellent b-selectivity was achieved
when m-bromocinnamate was subjected to hinge-tethered [2 + 2] cycloaddition.
Although two reactants are far apart in the open structure so that
the tether-attachment is easy, the closed hinge can be a scaffold to
Introduction
Tethered synthesis of organic compounds has been widely studied
stabilize the near-TS structure.
to improve regio- and stereoselectivities in the syntheses of
We have developed hinge-like molecules employing the ring flip
macromolecules and natural products.1 Its principle lies in the
constraint of two reacting components within a short distance (A
and B in Fig. 1a), which magnifies the effective concentration of
the reactants and stabilizes the transition-state (TS) structures,
speeding up the reaction usually with increased or different
selectivities compared with the intermolecular counterparts. How-
ever, many tethers developed thus far have a sizable freedom of
internal motion, permitting the formation of a number of transient
structures besides the near-TS structures during the reactions. To
diminish potential side-product formation, one may need a tether
with a restricted and discontinuous motion. A molecular hinge is
one that enables this kind of motion; i.e., the switch between an
open structure and a closed near-TS structure as shown in Fig. 1b.
of b-xylopyranosides (Fig. 2).2 A b-xylopyranoside adopting the
4C1 chair conformation is regarded as an open-hinge, because all
the substituents are equatorially oriented and, if the molecular
components are attached to the 1,3- or 2,4-positions, they will
form an extended arrangement. On the other hand, when the same
xylopyranoside adopts a 1C4 conformation, it resembles a closed-
hinge and the molecular components at the 1,3- or 2,4-positions
are arranged in a stacked manner because the substituents are now
all in an axial orientation. In practice, when pyrene groups were
incorporated into the 2,4-positions of methyl b-xylopyranoside,
pyrene-stacking was made possible by this hinge-like motion.3
The population of the closed form was solvent-dependent and
thus we were able to open and close the hinge molecule by simply
changing solvents. These results prompted us to investigate the
use of the hinge molecule in the tethering system for the [2 + 2]
cycloaddition of cinnamate. This cycloaddition was selected as a
model reaction to evaluate the hinge tether because there are a
number of examples of tethered syntheses for comparison with
this reaction.4 In addition, the diaxial scaffold provided by the
hinge-tether seemed to fit the product-like TS structure of the
cycloaddition, which was assumed to be a stacked dimer of two
cinnamates.
Fig. 1 A coupling reaction between A and B assisted by a general tether
(a) and by a hinge-like tether (b).
Department of Life Science, Graduate School of Bioscience and Biotechnol-
ogy, Tokyo Institute of Technology, 4259 J2-10, Nagatsutacho, Midoriku,
Yokohama, 226-8501, Japan. E-mail: hyuasa@bio.titech.ac.jp; Fax: +81 45
924 5850; Tel: +81 45 924 5850
† Electronic supplementary information (ESI) available: NMR spectra for
new compounds are reported. See DOI: 10.1039/b609115f
Fig. 2 A b-xylopyranoside as a hinge molecule.
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was carried out with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
(DDQ) to give the desired 2,4-dicinnamate 5. The 1C4 population
of compound 5 and 2,4-dipyrenecarbonyl derivative had a similar
solvent-dependence:3 70%, 23%, and 22%, respectively for CDCl3,
CD3OD, and DMSO-d6 solutions, indicating that less polar
solvents tend to afford a greater population of the closed-form.
Solvent dependence has been attributed to the disturbance of a
hydrogen bond by a polar solvent and to aromatic stacking that
stabilizes the closed-hinge in a non-polar solvent, as suggested
for the 2,4-dipyrenecarbonyl derivative.3 The fact that there is a
Results and discussion
At first, we attempted to tether two cinnamates by the direct and
selective esterification of methyl xylopyranoside in the presence
of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride
(EDC), 4-(dimethylamino)pyridine (DMAP), and cinnamic acid.
However, the desired 2,4-dicinnamate was obtained in only
3 to 5% yields in DMF, pyridine, or toluene–pyridine, while
all the other possible isomers were produced at higher yields.
We thus decided to block the 3-OH group with a temporary
protecting group. We synthesized methyl 3-O-p-methoxybenzyl-
b-D-xylopyranoside 2 from the epoxide 1 through nucleophilic
ring opening with p-methoxybenzyloxide (Scheme 1).5 Although
1
smaller C4 population of 3-O-protected hinge 4 (51%) than the
deprotected counterpart 5 (70%) emphasizes the importance of
the hydrogen bond between 3-OH and 1-O in the stabilization of
the closed form. The following profiles can be drawn from the
above results: cinnamates are readily attachable to the uncrowded
open form of the hinge-tether. Immediately after attachment, the
hinge-tether automatically closes in 50% of the population. Fur-
ther closure of the hinge-tether is enhanced by the removal of the
3-OH blocking group and by dissolving it in a non-polar solvent.
We next undertook a [2 + 2] cycloaddition for the two
cinnamates of compound 5 to assess whether the closed-form of
the hinge-tether allows for an intramolecular coupling reaction.
Solutions of 5 in CHCl3, methanol or DMF were photoirradiated
at 313 nm with a band-filtered 500 W Hg(Xe) lamp. Only
the CHCl3 solution underwent a reaction. Disappearance of
compound 5 was confirmed after 44 h by UV absorption at 270 nm
and the reaction resulted in a mixture of four diastereomers 7A–D,
which were partially isolated by silica gel column chromatography.
1
the H NMR spectrum of 2 is complicated due to the overlap
of H2 and H3 signals, the coupling constants of J4,5a = 5.3 Hz
and J4,5b = 10 Hz are typical of the 4C1 conformation, indicating
that 2 sits in the “open-form”. Esterification of p-methoxybenzyl
ether 2 was performed with cinnamic acid, EDC, and DMAP to
give 3-O-protected dicinnamate 4 in 78% yield. In this reaction,
4-monocinnamate 3 was also obtained in 21% yield. The coupling
constants of compounds 3 and 4 were deduced to be 19% and
1
51% (Table 1) of the C4 populations, respectively, by previously
reported methods.2 A higher C4 population of 4 than 3 is most
1
likely due to stabilization caused by aromatic stacking (Fig. 3).
Deprotection of the 3-O-p-methoxybenzyl group of compound 4
1
From the integrals in the H NMR spectra, the yields of 7A–
D were determined to be 66%, 9%, 7%, and 5.5%, respectively.
Since determination of the stereochemistry of these compounds
by 1H NMR spectra seemed impractical, the product mixture
was transesterified with methanol to remove the hinge-tether. The
fractions including 7A and 7B diastereomers produced an identical
cyclobutane, whose structure was elucidated to be methyl b-
truxinate 8bby comparison with the reported 1H NMR spectrum.6
This result indicates that two major tethered adducts have the
structures 7A and 7B shown in Scheme 2, in which the hinge-
tether was connected in different orientations. Molecular models
suggest that 7B is more congested than 7A with regard to the space
between the benzene rings and the equatorial protons of H1 and
H5 (Fig. 4), accounting for the large downfield shifts of H1 and
H5b in the 1H NMR spectrum of the cycloadduct 7B owing to ring
current effects. A fraction containing three products (7A, 7C and
7D) produced methyl b-, d-, and n-truxinates on transesterification.
However, we could not determine the stereochemistry of 7C
out of two possible diastereomers and 7D out of four possible
diastereomers. Overall, the product ratio of methyl b-, d-, and n-
truxinates (8b, d, n) in this hinge-tethered synthesis was 86 : 8 : 6.
All the isomers are head-to-head adducts derived from 5 with the
b- and d-isomers being E–E adducts and the n-isomer being a E–Z
adduct as shown in Scheme 2. The regio- and stereoselectivities are
comparable to those reported by others for tethered cinnamates,4
though a few studies demonstrated the exclusive formation of
b- and d-truxinates from the tethered dicinnamates 97 and 10,8
respectively (Chart 1). Though the n-isomer is asymmetric, we
were unable to elucidate the stereochemistry because neither the
tethered-cycloadduct 7D nor the released-cycloadduct 8n could
be separated from the other diastereomers. The production of
Scheme
1 Synthesis of 2,4-dicinnamate derivatives of methyl
3-O-p-methoxybenzyl-b-D-xylopyranoside (2). Reagents and conditions:
(a) PMBO−Na+; (b) CinOH, EDC, DMAP; (c) Cind7OH, SO2Cl2, TEA;
(d) mBrCinOH, EDC, DMAP; (e) DDQ.
Fig. 3 Importance of aromatic stacking and hydrogen bonding for the
formation of the closed-hinge.
Table 1 J-Values (Hz) and 1C4 population of xylopyranoside derivatives
Compound
Solvent
J1,2
J2,3
J3,4
J4,5a
J4,5b
1C4
2
3
4
5
5
5
CDCl3
CDCl3
CDCl3
CDCl3
CD3OD
DMSO-d7
—
—
—
5.3
5.2
3.8
3.4
4.7
5.2
10.2
0%
6.7
4.7
3.7
6.6
7.3
8.5
6.1
5.3
8.4
8.6
8.5
6.1
5.3
8.4
8.6
8.9 19%
6.1 51%
4.6 70%
8.5 23%
7.8 22%
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Scheme 2
(Scheme 1). The esterification resulted in an incomplete reaction
to give two mono-cinnamates, 6 and 3d7, besides dicinnamate 4d14.
The esterification conditions used for the synthesis of compound 4
(EDC, DMAP) resulted in the exchange of D to H at the a-position
of the cinnamate. The conformation of 5d14 showed almost the
same solvent dependence as that of 5 and photoirradiation was
performed for the chloroform solution of 5d14 under the same
conditions as those for 5. The reaction produced four products
7d14A–D in 75% yield with a product ratio of 65 : 13 : 11 :
11. The stereoselectivity (b–d–n = 78 : 11 : 11) was similar to
that obtained with the all-H cycloadduct 7. These isomers had
Chart 1
1
1
singlet H1 signals in the H NMR spectra indicative of a C4
pyranose conformation. According to our observations, all the
1
b-xylopyranosides fixed in C4 showed singlet H-1 signals and
they became doublets when they were unfixed even with 75% 1C4
population.2,3 It was thus suggested that all the diastereomers were
produced through intramolecular cycloaddition.
During the photoirradiation study, we found that there was
a pre-equilibrium of the double-bond isomerization prior to
cyclization to afford Z–Z 5Z,Z (26%), E–Z 5E,Z (21%), and Z–E 5Z,E
(21%) dicinnamates, together with the cycloadducts 7 (7%) and the
recovery of 5 (17%) after 4 h photoirradiation (Scheme 3). Though
the isomers could not be isolated and complete conformational
analyses were unfeasible due to the signal overlaps in the 1H
NMR spectra, the larger J-values of H1 signals for 5Z,Z (5.2 Hz),
Fig. 4 Molecular models of compounds 7A (left) and 7B (right).
Numerals are lengths in angstrom between H1 or H5b and the nearest
peripheral proton of a benzene ring. The molecular models were optimized
by SYBYL force field using PC Spartan software.11
n-truxinate is rather unusual, since this isomer has been produced
in small quantities in non-tether reactions9 and has seldom been
obtained from tethered cinnamates.10 This isomer, and even some
of the other isomers, might have been produced in an intermolec-
ular cycloaddition. To assess this hypothesis, the cinnamates of
5 were replaced with the all-deuterated cinnamates. This would
facilitate the assignment of the pyranose protons in the 1H NMR
spectra and thus the determination of the ring conformation
5
E,Z, and 5Z,E (4.4 and 4.7 Hz) relative to 5 (3.7 Hz) indicate
1
that the incorporation of Z-cinnamate tends to reduce the C4
population. We thus postulate that the formation of the near-
TS structure is relatively difficult from Z-cinnamates12 probably
due to congestion, and therefore the formation of an E–E adduct
was favored despite a small proportion of precursor 5 during the
double-bond isomerization.
1
as to whether it is fixed in C4 or unfixed in a conformational
equilibrium. The di-d7-cinnamate 5d14 was prepared by subjecting
compound 2 to thionyl chloride, triethylamine, and cinnamic acid-
d7 and the subsequent removal of the p-methoxybenzyl group
Nakatsuji and coworkers found that the [2 + 2] cycloaddition of
m-bromocinnamates results exclusively in the E–E adducts.13 The
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Scheme 3
excellent stereoselectivity is explained by the reactivity–selectivity
Experimental
principle, where the electron-withdrawing group caused the lower
reactivity and higher selectivity compared to the non-substituted
cinnamate. To ensure that our tether system reproduces high
selectivity, we synthesized the hinge-tethered m-bromocinnamate
5Br from compound 2 through compound 4Br (Scheme 1).
Photoirradiation of 5Br was carried out under the same conditions
as for 5 to afford 7BrA and 7BrB in 67% and 4% yields, respectively.
The other adducts were not found in this case. Release of the
hinge unit from the mixture of 7BrA and 7BrB yielded only the
methyl b-truxinate derivative (8Brb). The stereochemistry of 8Brb
was determined by the similarity of its NMR spectra with that of
8b. These results demonstrate that the hinge-tether system affords
a practical stereoselectivity in cases where an appropriate substrate
is attached to the tether.
General
All solvents and reagents used were reagent grade and, in cases
where further purification was required, standard procedures14
were followed. Solution transfers where anhydrous conditions
were required were done under dry argon using syringes. Thin-
layer chromatograms (TLC) were performed on precoated silica
gel Merck 60-F254 plates (Art 5715) and visualized by quenching
of fluorescence and/or by charring after spraying with 1% CeSO4–
1.5% (NH4)6Mo7O24·4H2O–10% H2SO4. Column chromatogra-
phy was performed on Merck Kieselgel 60 (Art 7734), Wako gel
C-300, or Kanto Silica gel 60N (spherical, neutral) with the solvent
systems specified
Optical rotations were determined with a Horiba SEPA-200
using 1 dm or 0.1 dm length cell. 1H NMR (1D, COSY, HMQC,
and HMBC) spectra were recorded at 400 MHz (Varian Unity-
400) or 270 MHz (JEOL EX-270). Internal tetramethylsilane (d
0 ppm) was used as a standard in CDCl3 or solvents peaks were
used as standards (d 2.50 ppm in DMSO-d6 or d 2.75 in DMF-d7).
Chemical shifts are expressed in ppm referenced to the solvent,
as an internal standard. Coupling constants are measured in Hz.
The multiplicity of signals is abbreviated as follows: s = singlet,
d = doublet, dd = doublet of doublets, t = triplet, dt = doublet of
triplets, ddd = doublet of doublets of doublets, br = broad signal,
m = multiplet. 13C NMR spectra were recorded at 67.8 MHz
(JEOL JNM-EX-270) or 100.6 MHz (Varian Unity-400) and
solvent peaks were used as standards (d 77.0 ppm in CDCl3 or
d 29.76 in DMF-d7). High resolution mass spectra (HRMS) were
recorded on Mariner Biospectrometry Workstation ESI-TOF MS.
Conclusions
We developed a novel hinge-type tether for the [2 + 2] cycloaddition
of cinnamate, in which a two-step closing procedure is employed
as shown in Fig. 5. The cinnamates were feasibly incorporated
into the partially protected hinge sugar in a polar solvent,
since the hinge molecule is mostly opened and uncrowded.
Deprotection (1st stage) and the use of a non-polar solvent
(2nd stage) promote the closure of the hinge molecule with
the assistance of hydrogen-bonding and aromatic stacking. The
[2 + 2] cycloaddition of hinge-tethered cinnamates proceeded
efficiently with this closed scaffold in a stereoselective manner. The
use of m-bromocinnamates afforded b-truxinate exclusively after
removal from the hinge molecule. Overall, the carbohydrate-tether
can intentionally generate a switching motion between open (or
uncrowded) and closed (or near-transition-state) forms, providing
a conceptually new tethering system.
Methyl 3-O-p-methoxybenzyl-b-D-xylopyranoside, 2. A mix-
ture of 55% NaH (75 mg, 1.71 mmol), which was washed
several times with hexane to remove the coated oil prior to use,
Fig. 5 The two-step closing system for the hinge-tethered photocycloaddition of cinnamates.
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and p-methoxybenzyl alcohol (2.1 mL, 16.8 mmol) was stirred
for 15 min at 0 ◦C. To this suspension was dropped a solution of
methyl 2,3-anhydro-b-D-ribopyranoside (1, 50 mg, 0.342 mmol)
in THF (2 mL) and the mixture was stirred for 50 min at room
temperature and 3.5 h at 70 ◦C. The mixture was poured into ice-
water and extracted with CHCl3. The organic layer was washed
successively with aqueous NH4Cl and brine, dried over MgSO4,
and evaporated. The residue was purified by silica-gel column
chromatography (hexane–ethyl acetate, 3 : 1 to 2 : 3) to give 2
(69 mg, 71%) as a white solid: Rf 0.15 (hexane–ethyl acetate, 1 :
1), mp 140–143 ◦C; [a]D22 −37.6 (c 1.00 in MeOH); dH (270 MHz,
CD3OD) 7.35 (2H, d, J 8.8, Ar), 6.87 (2H, d, J 8.8, Ar), 4.81 (1H,
d, J 11.2, CH2Ph), 4.78 (1H, d, J 11.2, CH2Ph), 4.13 (1H, d, J
7.5, 1-H), 3.86 (1H, dd, J 11.4, J 5.3, 5-Ha), 3.78 (3H, s, PhOMe),
3.63–3.37 (1H, m, 4-H), 3.49 (3H, s, OMe), 3.32–3.27 (2H, m,
2-H, 3-H), 3.21 (1H, dd, J 11.4, J 10.2, H-5b); dC (67.8 MHz,
CD3OD) 160.7, 132.3, 130.8, 130.7, 114.7, 114.5, 106.2 (C1), 85.4,
75.5 (CH2Ph), 74.8, 71.1 (C4), 66.9 (C5), 57.2 (Me), 55.7 (Me);
HRMS (ESI) Found: 307.1172 [M + Na]+. Calc. for C14H20O6Na
307.1158.
(3H, s, PhOMe), 3.53 (1H, dd, J4,5b 6.1, J5a,5b 12.1, 5-Hb), 3.48
=
=
(3H, s, OMe); dC (67.8 MHz, CDCl3) 165.7 (C O), 165.3 (C O),
159.1, 145.6, 145.6, 134.0, 134.0, 134.0, 130.4, 130.3, 129.7, 129.5,
128.8, 128.8, 128.1, 128.0, 117.4, 113.7, 100.7 (C1), 75.2 (C3), 72.6
(CH2Ph), 70.3 (C2), 69.7 (C4), 60.5 (C5), 56.3 (Me), 55.1 (Me);
HRMS (ESI) Found: 567.1999 [M + Na]+. Calc. for C32H32O8Na
567.1995.
Methyl 2,4-di-O-(E)-cinnamoyl-b-D-xylopyranoside, 5. To a
stirred solution of compound 4 (84 mg, 0.154 mmol) in CH2Cl2–
H2O (18 : 1, 5 mL) was added 2,3-dicholoro-5,6-dicyano-1,4-
benzoquinone (DDQ; 40 mg, 0.176 mmol) at 0 ◦C and the mixture
was further stirred for 9 h at room temperature. The mixture was
diluted with CHCl3–H2O and the organic layer was washed with
sat. NaHCO3 and then brine, dried over MgSO4, and evaporated.
The residue was purified by silica-gel column chromatography
(hexane–ethyl acetate, 6 : 1 to 5 : 2) to give compound 5 (62 mg,
95%) as an amorphous solid: Rf 0.16 (hexane–ethyl acetate, 3 : 1);
mp 56–58 ◦C; [a]D22 −41.5 (c 1.27 in CHCl3); dH (400 MHz, CDCl3)
=
=
7.77 (1H, d, J 16.0, PhHC C), 7.75 (1H, d, J 16.5, PhHC C),
=
7.44–7.25 (10H, m, Ar), 6.48 (1H, d, J 16.0, COHC C), 6.46 (1H,
=
d, J 16.5, COHC C), 4.99–4.96 (2H, m, 2-H, 4-H), 4.74 (1H, d,
1,2 3.7, 1-H), 4.26 (1H, dd, J4,5a 3.4, J5a,5b 12.8, 5-Ha), 4.05 (1H, dt,
Methyl
xylopyranoside, 4.
2,4-di-O-(E)-cinnamoyl-3-O-p-methoxybenzyl-b-D-
solution of cinnamic acid (70 mg,
J
A
J2,3 = J3,4 5.3, J3,OH 8.1, 3-H), 3.71 (1H, dd, J4,5b 4.6, J5a,5b 12.8, 5-
0.472 mmol) and SOCl2 (138 lL, 1.89 mmol) in dry toluene
(2.5 mL) was stirred for 2 h at 80 ◦C. After the solution was
evaporated, the residue was dried under vacuum for 1 h and
dissolved in CH2Cl2 (1.0 mL), to which was added a solution
of compound 2 (45 mg, 0.158 mmol) in CH2Cl2–pyridine (2 :
1, 1.5 mL) at 0 ◦C. The solution was stirred for 2 h at room
temperature and then 2 h at 40 ◦C. The mixture was poured into
ice-water and extracted with CHCl3. The organic layer was washed
successively with aqueous NH4Cl, aqueous NaHCO3, and brine,
dried over MgSO4, and evaporated. The residue was purified by
silica-gel column chromatography (hexane–ethyl acetate, 4 : 1 to
2 : 1) to give methyl 4-O-(E)-cinnamoyl-3-O-p-methoxybenzyl-b-
D-xylopyranoside (3, 14 mg, 21%) and 2,4-dicinnamate 4 (67 mg,
78%) as solids.
Hb), 3.52 (3H, s, OMe), 3.25 (1H, d, J3,OH 8.1, OH); dH (400 MHz,
=
CD3OD) 7.76 (1H, d, J 16.0, PhHC C), 7.745 (1H, d, J 16.5,
=
PhHC C), 7.60–7.57 (4H, m, Ar), 7.40–7.25 (6H, m, Ar), 6.56
=
(2H, d, J 16.0, COHC C × 2), 4.93–4.89 (2H, m, 2-H, 4-H), 4.53
(1H, d, J1,2 6.6, 1-H), 4.17 (1H, dd, J4,5a 4.7, J5a,5b 11.6, 5-Ha), 3.94
(1H, t, J2,3 = J3,4 8.4, 3-H), 3.48 (1H, dd, J4,5b 8.5, J5a,5b 11.6, 5-Hb),
3.47 (3H, s, OMe); dH (400 MHz, DMSO-d6) 7.73–7.67 (6H, m,
=
Ar, PhHC C × 2), 7.56–6.40 (6H, m, Ar), 6.66 (1H, d, J 16.0,
=
=
COHC C), 6.65 (1H, d, J 16.0, COHC C), 5.69 (1H, d, J3,OH
5.9, OH), 4.82–4.76 (2H, m, 2-H, 4-H), 4.51 (1H, d, J1,2 7.3, 1-H),
4.02 (1H, dd, J4,5a 5.2, J5a,5b 11.6, 5-Ha), 3.82 (1H, dt, J2,3 = J3,4
8.6, J3,OH 5.9, 3-H), 3.41 (1H, dd, J4,5b 7.8, J5a,5b 11.6, 5-Hb), 3.37
=
=
(3H, s, OMe); dC (67.8 MHz, CDCl3) 166.2 (C O), 165.9 (C O),
146.1, 145.9, 134.0, 134.0, 130.5, 130.5, 128.9, 128.1, 128.1, 117.4,
117.1, 99.9 (C1), 77.2, 70.4 (C4), 70.2 (C2), 68.2 (C3), 59.3 (C5),
56.2 (Me); HRMS (ESI) Found: 425.1635 [M + H]+. Calc. for
C24H25O7 425.1601.
◦
3. Rf 0.26 (hexane–ethyl acetate, 3 : 2); mp 113–115 C; [a]D22
−48.2 (c 0.45 in CHCl3); dH (400 MHz, CDCl3) 7.67 (1H, d, J
=
16.0Hz, PhHC C), 7.54–7.50 (2H, m, Ar), 7.42–7.38 (3H, m,
Ar), 7.27–7.24 (2H, m, Ar), 6.84–6.81 (2H, m, Ar), 6.36 (1H, d, J
=
16.0, COHC C), 5.05 (1H, ddd, J3,4 8.5, J4,5a 5.2, J4,5b 8.9, 4-H),
Methyl
2,4-di-O-(E)-cinnamoyl-d7-3-O-p-methoxybenzyl-b-
4.73 (2H, s, CH2Ph), 4.25 (1H, d, J1,2 6.7, 1-H), 4.15 (1H, dd, J4,5a
5.2, J5a,5b 11.7, 5-Ha), 3.72 (3H, s, PhOMe), 3.63 (1H, t, J 8.5, 3-
H), 3.61–3.56 (1H, bt, 2-H), 3.54 (3H, s, OMe), 3.31 (1H, dd, J4,5b
8.9, J5a,5b 11.7, 5-Hb), 2.51 (1H, b, OH); dC (67.8 MHz, CDCl3)
D-xylopyranoside, 4d14. A solution of (E)-cinnamic-d7 acid
(60 mg, 0.387 mmol) and SOCl2 (231 lL, 3.17 mmol) in dry
toluene (2.5 mL) was stirred for 2 h at 80 C. After the solution
◦
was evaporated, the residue was dried under vacuum for 1 h
and dissolved in CH2Cl2 (1.5 mL). In parallel, compound 2
(50 mg, 0.176 mmol) was co-evaporated with D2O–acetone-d6
(1 : 1) and dissolved in CH2Cl2–pyridine (2 : 1, 1.5 mL). The
solution of 2 was carefully added to the cinnamic-d7 chloride
solution at 0 ◦C. The mixture was further stirred for 1 h at room
temperature and then for 24 h at 40 ◦C. The mixture was poured
into ice-water and extracted with CHCl3. The organic layer was
washed successively with aqueous NH4Cl, aqueous NaHCO3,
and brine, dried over MgSO4, and evaporated. The residue was
purified by silica-gel column chromatography (hexane–ethyl
acetate, 4 : 1 through 2 : 1 to 2 : 3) to give methyl 4-O-(E)-
=
166.0 (C O), 146.0, 134.4, 130.8, 130.5, 129.8, 129.2, 128.4, 117.5,
114.1, 104.2 (C1), 80.0 (C3), 74.0 (CH2Ph), 73.5 (C2), 71.3 (C4),
62.8 (C5), 57.1 (Me), 55.4 (Me); HRMS (ESI) Found: 437.1578
[M + Na]+. Calc. for C23H26O7Na 437.1576.
4. Rf 0.24 (hexane–ethyl acetate, 3 : 1); mp 125–127 C; [a]D22
◦
−78.3 (c 0.635 in CHCl3); dH (400 MHz, CDCl3) 7.73 (1H, d, J
=
=
16.0, PhHC C), 7.69 (1H, d, J 16.5, PhHC C), 7.49–7.44 (4H,
m, Ar), 7.41–7.29 (6H, m, Ar), 7.26–7.23 (2H, m, Ar), 6.82–6.79
=
(2H, m, Ar), 6.43 (1H, d, J 16.0, COHC C), 6.40 (1H, d, J 16.5,
COHC C), 5.15 (1H, dd, J1,2 4.7, J2,3 6.1, 2-H), 5.05 (1H, ddd,
J3,4 6.2, J4,5a 3.8, J4,5b 6.1, 4-H), 4.69 (1H, d, J 11.8, CH2Ph),
4.64 (1H, d, J 11.8, CH2Ph), 4.58 (1H, d, J1,2 4.7, 1-H), 4.27
(1H, dd, J4,5a 3.8, J5a,5b 12.1, 5-Ha), 3.82 (1H, t, J 6.2, 3-H), 3.69
=
cinnamoyl-d7-3-O-p-methoxybenzyl-b-D-xylopyranoside
21 mg, 28%), 2,4-dicinnamate-d7 4d14 (32 mg, 33%), and methyl
(3d7,
3698 | Org. Biomol. Chem., 2006, 4, 3694–3702
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2-O-(E)-cinnamoyl-d7-3-O-p-methoxybenzyl-b-D-xylopyranoside
(6, 14 mg, 19%) as solids.
3-bromocinnamic acid (176 mg, 0.775 mmol), 1-(3-dimethyl-
aminopropyl)-3-ethylcarbodiimide hydrochloride (EDC; 148 mg,
0.772 mmol) and 4-(dimethylamino)pyridine (DMAP; 95 mg,
0.778 mmol) in DMF (3.5 mL) was stirred for 24 h at room
temperature. The mixture was poured into ice-water and ex-
tracted with CHCl3. The organic layer was washed successively
with 0.5 M HCl, aqueous NaHCO3, and brine, dried over
MgSO4, and evaporated. The residue was purified by silica-gel
column chromatography (hexane–ethyl acetate, 7 : 2 to 2 : 1)
to give methyl 4-O-(E)-3-bromocinnamoyl-3-O-p-methoxybenzyl-
b-D-xylopyranoside (3Br, 29 mg, 17%) as a solid and 2,4-
dicinnamate 4Br (199 mg, 80%) as a syrup.
3d7. Rf 0.26 (hexane–ethyl acetate, 1.5 : 1); mp 113–115 ◦C;
[a]2D2 −88.6 (c 0.525 in CHCl3); dH (400 MHz, CDCl3) 7.28–7.24
(2H, m, Ar), 6.85–6.81 (2H, m, Ar), 5.06 (1H, dt, J4,5a 5.2, J3,4
=
J4,5b 8.9, 4-H), 4.73 (2H, s, CH2Ph), 4.26 (1H, d, J1,2 6.7, 1-H),
4.15 (1H, dd, J4,5a 5.2, J5a,5b 11.8, 5-Ha), 3.72 (3H, s, PhOMe),
3.64 (1H, t, J2,3 = J3,4 8.9, 3-H), 3.58 (1H, bt, 2-H), 3.54 (3H, s,
Me), 3.31 (1H, dd, J4,5b 8.9, J5a,5b 11.8, H-5b), 2.47 (1H, b, OH);
=
dC (67.8 MHz, CDCl3) 165.8 (C O), 159.3, 133.8, 130.2, 130.0,
129.6, 128.8, 128.4, 128.1, 127.7, 127.4, 113.8, 104.0 (C1), 79.8
(C3), 77.2, 73.8 (CH2Ph), 73.3 (C2), 71.0 (C4), 62.6 (C5), 57.0
(Me), 55.1 (Me); HRMS (ESI) Found: 444.2000 [M + Na]+. Calc.
for C23H19D7O7Na 444.2016.
3Br. Rf 0.375 (hexane–ethyl acetate, 1 : 1); mp 148–150 ◦C; [a]D22
−40.7 (c 0.625 in CHCl3); dH (400 MHz, CDCl3) 7.67–7.24 (7H,
4d14. Rf 0.24 (hexane–ethyl acetate, 3 : 1); mp 124–126 ◦C; [a]D22
−47.4 (c 0.515 in CHCl3); dH (400 MHz, CDCl3) 7.26–7.23 (2H,
m, Ar), 6.82–6.79 (2H, m, Ar), 5.10 (1H, dd, J1,2 4.7, J2,3 6.3, 2-H),
5.05 (1H, dt, J4,5a 3.8, J3,4 = J4,5b 6.3, 4-H), 4.69 (1H, d, J 11.8,
CH2Ph), 4.65 (1H, d, J 11.8, CH2Ph), 4.58 (1H, d, J1,2 4.7 Hz, 1-
H), 4.26 (1H, dd, J4,5a 3.8, J5a,5b 12.2, 5-Ha), 3.82 (1H, t, J2,3 = J3,4
6.3, 3-H), 3.69 (3H, s, PhOMe), 3.54 (1H, dd, J4,5b 6.3, J5a,5b 12.2, 5-
=
m, Ar, PhHC C × 2), 6.84–6.81 (2H, m, Ar), 6.33 (1H, d, J 16.0,
=
COHC C), 5.05 (1H, ddd, J3,4 6.9, J4,5a 5.3, J4,5b 9.1, 4-H), 4.75
(1H, d, J 12.5, CH2Ph), 4.70 (1H, d, J 12.5, CH2Ph), 4.25 (1H,
d, J1,2 6.3 Hz, 1-H), 4.14 (1H, dd, J4,5a 5.3, J5a,5b 11.7, 5-Ha), 3.73
(3H, s, PhOMe), 3.62 (1H, t, J2,3 = J3,4 6.9, 3-H), 3.62–3.57 (1H,
m, 2-H), 3.54 (3H, s, OMe), 3.30 (1H, dd, J4,5b 9.1, J5a,5b 11.7, 5-
=
Hb), 2.45 (1H, b, OH); dC (67.8 MHz, CDCl3) 165.4 (C O), 159.3,
=
Hb), 3.48 (3H, s, OMe); dC (67.8 MHz, CDCl3) 166.1 (C O), 165.7
143.9, 136.2, 133.3, 130.8, 130.4, 130.2, 129.7, 126.8, 123.1, 118.8,
113.8, 104.0 (C1), 79.8 (C3), 73.8 (CH2Ph), 73.3 (C2), 71.1 (C4),
62.6 (C5), 56.9 (Me), 55.2 (Me); HRMS (ESI) Found: 515.0710
[M + Na]+. Calc. for C23H25O7BrNa 515.0682.
=
(C O), 159.4, 134.0, 129.8, 128.6, 127.9, 127.7, 117.5, 113.9, 101.0
(C1), 75.4 (C3), 72.9 (CH2Ph), 70.4 (C2), 69.9 (C4), 60.7 (C5), 56.5
(Me), 55.3 (Me); HRMS (ESI) Found: 581.2851 [M + Na]+. Calc.
for C32H18D14O8Na 581.2873.
6. Rf 0.19 (hexane–ethyl acetate, 1.5 : 1); mp 62–64 C; [a]D22
4Br. Rf 0.34 (hexane–ethyl acetate, 2 : 1); [a]2D2 −30.0 (c 2.34,
◦
=
CHCl3); dH (400 MHz, CDCl3) 7.63–6.17 (12H, m, Ar, PhHC C ×
−2.6 (c 0.38 in CHCl3); dH (400 MHz, CDCl3) 7.26–7.22 (2H, m,
Ar), 6.86–6.82 (2H, m, Ar), 5.08 (1H, dd, J1,2 6.0, J2,3 7.5, 2-H),
4.72 (1H, d, J 11.5, CH2Ph), 4.56 (1H, d, J 11.5, CH2Ph), 4.44
(1H, d, J1,2 6.0, 1-H), 4.10 (1H, dd, J4,5a 4.3, J5a,5b 11.6, 5-Ha),
=
2), 6.82–6.78 (2H, m, Ar), 6.37 (1H, d, J 16.2, COHC C), 6.37
=
(1H, d, J 16.2, COHC C), 5.10 (1H, dd, J1,2 5.1, J2,3 6.6, 2-
H), 5.06 (1H, ddd, J3,4 6.6, J4,5a 4.0, J4,5b 6.8, 4-H), 4.65 (2H, s,
CH2Ph), 4.54 (1H, d, J1,2 5.1, H-1), 4.25 (1H, dd, J4,5a 4.0, J5a,5b
12.0, 5-Ha), 3.81 (1H, t, J2,3 = J3,4 6.6, 3-H), 3.69 (3H, s, PhOMe),
3.49 (1H, dd, J4,5b 6.8, J5a,5b 12.0 Hz, 5-Hb), 3.48 (3H, s, OMe);
3.81–3.72 (1H, m, 4-H), 3.74 (3H, s, PhOMe), 3.56 (1H, t, J2,3
=
J
3,4 7.5, 3-H), 3.47 (3H, s, OMe), 3.37 (1H, dd, J4,5b 8.1, J5a,5b 11.6,
=
5-Hb), 2.40 (1H, b, OH); dC (67.8 MHz, CDCl3) 165.7 (C O),
159.6, 134.1, 130.2, 129.9, 117.4, 114.2, 102.0 (C1), 80.2 (C3),
77.4, 73.6 (CH2Ph), 71.8 (C2), 69.0 (C4), 64.1 (C5), 56.7 (Me),
55.4 (Me); HRMS (ESI) Found: 444.2013 [M + Na]+. Calc. for
C23H19D7O7Na 444.2016.
=
=
dC (67.8 MHz, CDCl3) 165.3 (C O), 164.9 (C O), 159.2, 143.9,
143.8, 136.2, 136.1, 133.3, 133.2, 130.7, 130.4, 130.4, 129.7, 129.5,
126.7, 126.6, 123.0, 123.0, 118.9, 118.8, 113.7, 100.9 (C1), 75.7
(C3), 72.8 (CH2Ph), 70.8 (C2), 70.1 (C4), 60.7 (C5), 56.2 (Me),
55.1 (Me); HRMS (ESI) Found: 723.0196 [M + Na]+. Calc. for
C32H30O8Br2Na 723.0206.
Methyl 2,4-di-O-(E)-cinnamoyl-d7-b-D-xylopyranoside, 5d14.
To a stirred solution of 4d14 (31.0 mg, 0.055 mmol) in CH2Cl2–
H2O (18 : 1, 1.0 mL) was added DDQ (14 mg, 0.62 mmol) at 0 ◦C
and the mixture was further stirred for 11 h at room temperature.
The mixture was diluted with CHCl3–H2O and the organic layer
was washed with sat. NaHCO3 and then brine, dried over MgSO4,
and evaporated. The residue was purified by silica-gel column
chromatography (hexane–ethyl acetate, 6 : 1 to 5 : 2) to give
compound 5d14 (23 mg, 95%) as an amorphous solid: Rf 0.30
Methyl
2,4-di-O-(E)-3-bromocinnamoyl-b-D-xylopyranoside,
5Br. To a stirred solution of 4Br (182 mg, 0.258 mmol) in
CH2Cl2–H2O (18 : 1, 4 mL) was added DDQ (93 mg, 0.410 mmol)
at 0 ◦C and the mixture was further stirred for 5 h at room
temperature. The mixture was diluted with CHCl3–H2O and the
organic layer was washed with sat. NaHCO3 and then brine,
dried over MgSO4, and evaporated. The residue was purified by
silica-gel column chromatography (hexane–ethyl acetate, 5 : 1 to
5 : 2) to give compound 5Br (135 mg, 90%) as a syrup: Rf 0.265
(hexane–ethyl acetate, 2 : 1); [a]2D2 −28.1 (c 1.375 in CHCl3); dH
◦
(hexane–ethyl acetate, 2 : 1); mp 56–58 C; [a]2D2 −42.6 (c 1.00 in
CHCl3); dH (270 MHz, CDCl3) 5.00–4.96 (2H, m, 2-H, 4-H), 4.74
(1H, d, J1,2 3.7, 1-H), 4.26 (1H, dd, J4,5a 3.6, J5a,5b 12.8, 5-Ha),
4.05 (1H, b, 3-H), 3.70 (1H, dd, J4,5b 4.1, J5a,5b 12.8, 5-Hb), 3.52
(3H, s, OMe), 3.29 (1H, b, OH); dC (67.8 MHz, CDCl3) 166.2
=
(270 MHz, CDCl3) 7.65 (1H, d, J 15.9, PhHC C), 7.64 (1H,
=
d, J 15.9, PhHC C), 7.584 (1H, s, 2-H-BrPh), 7.580 (1H, s,
2-H-BrPh), 7.476 (1H, d, J 7.8, 4-H-BrPh), 7.474 (1H, d, J 7.8,
4-H-BrPh), 7.328 (1H, d, J 7.8, 6-H-BrPh), 7.325 (1H, d, J 7.8,
6-H-BrPh), 7.172 (1H, d, J 7.8, 5-H-BrPh), 7.165 (1H, t, J 7.8,
=
=
(C O), 165.9 (C O), 146.0, 145.7, 145.4, 133.7, 128.7, 128.3,
128.0, 127.7, 127.4, 117.0, 99.9 (C1), 70.4, 70.2, 68.2 (C3), 59.3
(C5), 56.2 (Me); HRMS (ESI) Found: 461.2280 [M + Na]+. Calc.
for C24H10D14O7Na 461.2298.
=
5-H-BrPh), 6.44 (2H, d, J 15.9, COHC C × 2), 5.01–4.96 (2H,
m, 2-H, 4-H), 4.69 (1H, d, J1,2 4.1, 1-H), 4.25 (1H, dd, J4,5a 3.5,
J5a,5b 12.8, 5-Ha), 4.03 (1H, dt, J2,3 = J3,4 5.3, J3,OH 7.9, 3-H),
3.66 (1H, dd, J4,5b 5.0, J5a,5b 12.8 Hz, 5-Hb), 3.50 (3H, s, OMe),
Methyl 2,4-di-O-(E)-3-bromocinnamoyl-3-O-p-methoxybenzyl-
b-D-xylopyranoside, 4Br. A mixture of 2 (100 mg, 0.352 mmol),
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3.32 (1H, d, J3,OH 7.9 Hz, OH); dH (270 MHz, CD3OD) 7.75
(C5ꢀ), 59.9 (C5ꢀꢀ), 56.3 (Me); HRMS (ESI) Found: 447.1440 [M +
Na]+. Calc. for C24H24O7Na 447.1421.
=
(2H, s, 2-H-BrPh), 7.68 (1H, d, J 16.0, PhHC C), 7.67 (1H, d,
=
J 16.0, PhHC C), 7.55–7.53 (4H, m, Ar), 7.296 (1H, t, J 7.8,
Fr3 (15 mg) includes 5, 5E,Z, 5Z,E, and 5Z,Z in the ratio 0.47 : 0.24 :
5-H-BrPhh), 7.292 (1H, t, J 7.8, 5-H-BrPh), 6.69 (1H, d, J 16.0,
0.15 : 0.14; [a]2D2 −34.0 (c 0.75 in CHCl3).
=
=
COHC C), 6.68 (1H, d, J 16.0, COHC C), 4.93–4.88 (2H, m,
2-H, 4-H), 4.54 (1H, d, J1,2 6.6, 1-H), 4.17 (1H, dd, J4,5a 4.9, J5a,5b
11.7, 5-Ha), 3.95 (1H, t, J2,3 = J3,4 8.2, 3-H), 3.48 (1H, dd, J4,5b
Photoirradiation of compound 5 for 44 h. A solution of
compound 5 (30 mg, 0.071 mmol) in CHCl3 (3 mL), which was
bubbled with argon gas prior to the reaction, was irradiated for
44 h at 16 ◦C with a 500 W Hg(Xe) lamp (band-filtered at 313 nm).
After removal of the solvent, the residue was chromatographed on
silica-gel (toluene–ethyl acetate, 5 : 1) to give four fractions (Fr1,
Fr2, Fr3, Fr4) each containing the isomeric mixture of methyl
b-D-xylopyranoside-2,4-truxinates (7).
1
8.6, J5a,5b 11.7, 5-Hb), 3.47 (3H, s, OMe); H NMR (270 MHz,
DMSO-d6) 7.992 (1H, s, 2-H-BrPh), 7.987 (1H, s, 2-H-BrPh),
=
7.75 (2H, d, J 7.8, 4-H-BrPh), 7.68 (1H, d, J 16.0, PhHC C),
=
7.66 (1H, d, J 16.0, PhHC C), 7.62 (2H, d, J 7.8, 6-H-BrPh),
7.373 (1H, t, J 7.8, 5-H-BrPh), 7.368 (1H, t, J 7.8, 5-H-BrPh),
=
=
6.76 (1H, d, J 16.1, COHC C), 6.75 (1H, d, J 16.1, COHC C),
5.70 (1H, b, OH), 4.83–4.77 (1H, m, 4-H), 4.78 (1H, dd, J1,2
7.3, J2,3 8.7, 2-H), 4.51 (1H, d, J1,2 7.3, 1-H), 4.01 (1H, dd, J4,5a
6.1, J5a,5b 11.6, 5-Ha), 3.80 (1H, bt, 3-H), 3.46–3.34 (4H, m,
Fr1 (2 mg) includes
a single isomer of methyl b-D-
xylopyranoside-2,4-b-truxinate (7B) as a syrup; Rf 0.40 (hexane–
ethyl acetate, 2 : 1); [a]D22 −44.3 (c 0.08 in CHCl3); dH (400 MHz,
CDCl3) 7.14–7.03 (6H, m, Ar), 6.93–6.88 (4H, m, Ar), 5.11 (1H, s,
1-H), 4.75–4.74 (1H, m, 2-H), 4.73–4.71 (1H, m, 4-H), 4.70–4.68
=
=
5-Hb, OMe); dC (67.8 MHz, CDCl3) 165.7 (C O), 165.5 (C O),
=
=
144.4 (PhC C), 144.2 (PhC C), 136.0, 133.3, 130.8, 130.4,
=
=
126.6, 123.0, 118.8 (COC C), 118.6 (COC C), 100.1 (C1), 70.8
(C4, C2), 68.6 (C3), 59.6 (C5), 56.3 (Me); HRMS (ESI) Found:
602.9616 [M + Na]+. Calc. for C24H22O7Br2Na 602.9631.
=
(2H, m, PhHC C × 2), 4.51–4.47 (1H, m, 3-H), 4.33 (1H, dd, J4,5a
1.5, J5a,5b 13.4, 5-Ha), 4.20–4.16 (1H, m, 5-Hb), 3.93–3.83 (2H, m,
=
COHC C × 2), 3.86 (1H, d, J3,OH 10.1, OH), 3.56 (3H, s, OMe);
=
=
Photoirradiation of compound 5 for 4 h. A solution of com-
pound 5 (41 mg, 0.097 mmol) in CHCl3 (4 mL), which was bubbled
with argon gas prior to the reaction, was irradiated for 4 h at
16 ◦C with a 500 W Hg(Xe) lamp (band-filtered at 313 nm).
After removal of the solvent, the residue was chromatographed on
silica-gel (hexane–ethyl acetate, 5 : 2 to 2 : 1) to give the isomeric
mixture of methyl b-D-xylopyranoside-2,4-truxinates (7; 3 mg, 7%)
and three fractions (Fr1, Fr2, Fr3) each containing the mixture in
different ratios of methyl 2-O-(Z)-cinnamoyl-4-O-(E)-cinnamoyl-
b-D-xylopyranoside (5Z,E; 21%), methyl 2-O-(E)-cinnamoyl-4-O-
(Z)-cinnamoyl-b-D-xylopyranoside (5E,Z; 21%), and methyl 2,4-
di-O-(Z)-cinnamoyl-b-D-xylopyranoside (5Z,Z; 26%).
dC (67.8 MHz, CDCl3) 174.4 (C O), 170.2 (C O), 138.3, 128.1,
128.1, 128.0, 127.9, 127.8, 127.6, 126.5, 126.4, 98.7 (C1), 73.0
(C2), 71.8 (C4), 60.2 (C3), 56.7 (C5), 56.1 (Me), 46.5 (cyclobutane),
46.2 (cyclobutane), 43.3 (cyclobutane), 43.1 (cyclobutane); HRMS
(ESI) Found: 447.1463 [M + Na]+. Calc. for C24H24O7Na 447.1421.
Fr2 (3 mg) includes two methyl b-D-xylopyranoside-2,4-b-
truxinates (7A and 7B) in the ratio 0.74 : 0.26; [a]2D2 −34.0 (c 0.15
in CHCl3).
Fr3 (14 mg) includes another isomer of methyl b-D-
xylopyranoside-2,4-b-truxinate (7A) as a syrup; Rf 0.36 (hexane–
ethyl acetate, 2 : 1); [a]D22 −35.6 (c 0.70 in CHCl3); dH (400 MHz,
CDCl3) 7.13–7.06 (6H, m, Ar), 6.93–6.88 (4H, m, Ar), 4.93 (1H,
d, J1,2 0.6, 1-H), 4.77–4.73 (2H, m, 2-H, 4-H), 4.58–4.47 (3H, m,
3-H, PhHCC × 2), 4.31 (1H, dd, J4,5a 1.4, J5a,5b 13.3, 5-Ha), 4.19–
4.08 (2H, m, COHCC × 2), 3.91–3.85 (1H, m, 5-Hb), 3.81 (1H,
d, J3,OH 9.9, OH), 3.54 (3H, s, OMe); dC (67.8 MHz, CDCl3) 171.7
(C O), 171.4 (C O), 138.3, 129.0, 128.7, 128.2, 127.8, 126.6,
126.3, 98.9 (C1), 71.8 (C2), 69.4 (C4), 59.3 (C3), 57.0 (C5), 56.1
(Me), 45.0 (cyclobutane), 44.9 (cyclobutane), 42.3 (cyclobutane);
HRMS (ESI) Found: 447.1422 [M + Na]+. Calc. for C24H24O7Na
447.1421.
Fr4 (7 mg) includes methyl b-D-xylopyranoside-2,4-b-truxinate
(7A), methyl b-D-xylopyranoside-2,4-d-truxinate (7C), and methyl
b-D-xylopyranoside-2,4-n-truxinate (7D), in the ratio 0.48 : 0.29 :
0.23; [a]2D2 −31.7 (c 0.36 in CHCl3); dH (400 MHz, CDCl3, H: 7A,
Hꢀ: 7C, Hꢀꢀ: 7D) COSY d 7.37–6.88 (10H, m, Ar), 4.93 (0.48H, s, 1-
H), 4.87 (0.29H, s, 1-Hꢀ), 4.85 (0.23H, s, 1-Hꢀꢀ), 4.77–4.73 (1.48H,
m, 2-H, 4-H, 2-Hꢀ, 4-Hꢀꢀ), 4.73–4.64 (0.58H, m, PhHꢀCC × 2),
4.58–4.46 (1.94H, m, 3-H, PhHCC, 3-Hꢀ, 3-Hꢀꢀ, 2-Hꢀꢀ, 4-Hꢀꢀ), 4.33–
4.21 (1H, m, 5-Ha, 5-Hꢀa, 5-Hꢀꢀa), 4.19–4.08 (0.94H, m, PhHCC,
PhHꢀꢀCC × 2), 4.04–3.97 (0.58H, m, COHꢀCC × 2), 3.91–3.82
(0.77H, m, 5-Hb, 5-Hꢀb), 3.82–3.69 (2.42H, m, OH, OHꢀ, 5-Hꢀꢀb,
COHCC × 2, COHꢀꢀCC × 2), 3.60 (0.23H, d, J3,OH 9.6, OHꢀꢀ),
3.54 (1.44H, s, OMe), 3.51 (1.56H, s, OMeꢀ, OMeꢀꢀ); dC (67.8 MHz,
CDCl3) 171.4, 171.3, 171.0, 141.4, 138.7, 138.3, 129.0, 128.7, 128.2,
128.0, 127.8, 127.0, 126.7, 126.6, 126.3, 99.1, 98.9, 98.7, 71.8, 71.6,
69.4, 69.3, 59.3, 58.8, 58.6, 57.2, 57.0, 56.9, 56.1, 56.0, 46.8, 46.6,
Fr1 (6 mg) includes 5E,Z, 5Z,E, and 5Z,Z in the ratio 0.13 : 0.361 :
0.51; [a]2D2 −34.0 (c 0.75 in CHCl3).
Fr2 (13 mg) includes 5E,Z, 5Z,E, and 5Z,Z in the ratio 0.26 : 0.33 :
0.41; [a]2D2 −42.6 (c 0.63 in CHCl3); dH (400 MHz, CDCl3, H: 5Z,Z
,
ꢀꢀ
Hꢀ: 5Z,E, Hꢀꢀ: 5E,Z) 7.73 (0.26H, d, J 16.0, (E)–PhH C C), 7.72
=
=
=
ꢀ
=
(0.34H, d, J 16.0, (E)–PhH C C), 7.61–7.32 (10H, m, Ar), 7.03–
ꢀ
ꢀꢀ
=
=
=
6.96 (1.41H, m, (Z)–PhHC C, (Z)–PhH C C, (Z)–PhH C C),
ꢀ
=
6.43 (0.33H, d, J 16.0, (E)–COH C C), 6.42 (0.26H, d, J
ꢀꢀ
=
=
16.0, (E)–COH C C), 6.01–5.94 (1.41H, m, (Z)–COHC C, (E)–
ꢀ
ꢀꢀ
=
=
=
COHC C, (Z)–COH C C, (Z)–COH C C), 4.95–4.83 (2H, m,
2-H, 2-Hꢀ, 2-Hꢀꢀ, 4-H, 4-Hꢀ, 4-Hꢀꢀ), 4.59 (0.26H, d, J1,2 4.4, 1-Hꢀꢀ),
4.55 (0.33H, d, J1,2 4.7, 1-Hꢀ), 4.43 (0.41H, d, J1,2 5.2, 1-H), 4.20
(0.33H, dd, J4,5a 3.7, J5a,5b 12.7, 5-Hꢀa), 4.17 (0.26H, dd, J4,5a 4.0,
J
5a,5b 12.8, 5-Hꢀꢀa), 4.12 (0.41H, dd, J4,5a 4.1, J5a,5b 12.4, 5-Ha), 3.91–
3.87 (0.59H, m, 3-Hꢀ, 3-Hꢀꢀ), 3.75 (0.41H, bq, 3-H), 3.56 (0.33H, dd,
J4,5b 5.5, J5a,5b 12.7, 5-Hꢀb), 3.52 (0.26H, dd, J4,5b 5.6, J5a,5b 12.8, 5-
Hꢀꢀb), 3.49 (0.78H, s, OMeꢀꢀ), 3.48 (0.99H, s, OMeꢀ), 3.45 (1.23H, s,
OMe), 3.40 (0.41H, dd, J4,5b 6.4, J5a,5b 12.4, 5-Hb), 3.04 (0.33H,
d, J3,OH7.5, OHꢀꢀ), 3.01 (0.26H, d, J3,OH 7.5, OHꢀ), 2.81 (0.41H, d,
=
=
J
3,OH 7.0, OH); dC (67.8 MHz, CDCl3) 166.3 (C O), 166.0 (C O),
=
=
=
=
165.4 (C O), 165.4 (C O), 165.2 (C O), 165.1 (C O), 146.1,
145.9, 144.6, 144.5, 144.5, 134.6, 134.5, 134.5, 134.2, 130.5, 129.8,
129.7, 129.3, 129.3, 129.3, 128.9, 128.2, 128.1, 128.0, 118.9, 118.7,
118.6, 117.3, 117.2, 100.5 (C1), 100.4 (C1ꢀ), 100.2 (C1ꢀꢀ), 71.3, 71.0,
70.9, 70.8, 70.8, 69.9 (C3), 69.4 (C3ꢀ), 69.3 (C3ꢀꢀ), 60.4 (C5), 60.1
3700 | Org. Biomol. Chem., 2006, 4, 3694–3702
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45.7, 45.5, 45.0, 44.9, 44.1, 44.0, 42.3, 41.8, 29.7; HRMS (ESI)
Found: 425.1640 [M + H]+. Calc. for C24H25O7 425.1601.
CDCl3, H: 7d14A, Hꢀ: 7d14C, Hꢀꢀ: 7d14D) 4.90 (0.5H, s, 1-H), 4.84
(0.25H, s, 1-Hꢀ), 4.82 (0.25H, s, 1-Hꢀꢀ), 4.74–4.70 (1.5H, m, 2-H,
2-Hꢀ, 4-H, 4-Hꢀꢀ), 4.54–4.42 (1.5H, m, 3-H, 3-Hꢀ, 3-Hꢀꢀ, 2-Hꢀꢀ, 4-
Hꢀꢀ), 4.29–4.18 (1H, m, 5-Ha, 5-Hꢀa, 5-Hꢀꢀa), 3.87–3.73 (1.75H, m,
5-Hb, 5-Hꢀb, OH, OHꢀ, 5-Hꢀꢀb), 3.58 (0.25H, d, J3,OH 9.6, OHꢀꢀ),
3.51 (1.5H, s, OMe), 3.47 (1.5H, s, OMeꢀ, OMeꢀꢀ); dC (67.8 MHz,
CDCl3) 171.7, 171.4, 171.3, 170.9, 170.5, 141.1, 139.9, 139.7, 138.5,
138.4, 127.8, 127.7, 127.4, 127.1, 126.1, 125.8, 99.1 (C1), 98.9 (C1),
98.7 (C1), 71.8, 71.6, 69.4, 69.3, 59.2, 58.8, 58.6, 57.2, 57.0, 56.9,
56.1, 56.0, 29.7; HRMS (ESI) Found: 461.2286 [M + Na]+. Calc.
for C24H10D14O7Na 461.2298.
Ester exchange reaction for methyl b-D-xylopyranoside-2,4-
truxinates. A mixture of methyl b-D-xylopyranoside-2,4-b-
truxinates (7: 24 mg, 0.056 mmol) in Fr1, Fr2, Fr3 obtained in
the previous section were treated with SOCl2–MeOH (1 : 100,
5.0 mL) under argon gas for 3 days at room temperature. After
evaporation, the mixture was dissolved in CHCl3, washed with sat.
NaHCO3, dried over MgSO4, and evaporated to give b-truxinate
8b(15.5 mg, 85%) as a white solid: dH (400 MHz, CDCl3) 7.12–6.89
(10H, m, Ar), 4.41–4.39 (2H, m, PhHCC × 2), 3.86–3.84 (2H, m,
COHCC × 2), 3.75 (6H, s, OMe); dC (67.8 MHz, CDCl3) 172.9
Photoirradiation of compound 5Br for 44 h. A solution of
compound 5Br (46 mg, 0.079 mmol) in CHCl3 (3.5 mL), bubbled
with argon gas prior to the reaction, was irradiated for 44 h at
16 ◦C with a 500 W Hg(Xe) lamp (band-filtered at 313 nm).
After removal of the solvent, the residue was chromatographed
on silica-gel (hexane–ethyl acetate, 2 : 1 to 3 : 2) to give a
fraction (Fr1) containing the isomeric mixture of methyl b-
D-xylopyranoside-2,4-b-3,3ꢀ-dibromotruxinates (7BrA and 7BrB;
11 mg, 24%) and a single isomer of methyl b-D-xylopyranoside-
2,4-b-3,3ꢀ-dibromotruxinate 7BrA (20 mg, 43%) as a syrup.
7BrA. Rf 0.20 (hexane–ethyl acetate, 3 : 2); [a]2D2 −35.2 (c 1.00
in CHCl3); dH (400 MHz, CDCl3) 7.26–6.78 (8H, m, Ar), 4.93
(1H, s, 1-H), 4.76–4.72 (2H, m, 2-H, 4-H), 4.40–4.56 (3H, m, 3-H,
PhHCC × 2), 4.30 (1H, d, J5a,5b 13.3, 5-Ha), 4.05–4.13 (2H, m,
COHCC × 2), 3.89 (1H, d, J5a,5b 13.3 Hz, 5-Hb), 3.82 (1H, d, J3,OH
=
(C O), 138.4, 128.0, 127.7, 126.4, 52.2 (Me), 44.9 (cyclobutane),
43.2 (cyclobutane); HRMS (ESI) Found: 347.1264 [M + Na]+.
Calc. for C20H20O4Na 347.1260.
A mixture of b-truxinate 8b, d-truxinate 8d, and n-truxinate
8n (0.7 : 0.2 : 0.1) was obtained through the above treatment
from Fr4: dH (400 MHz, CDCl3) 7.36–6.92 (10H, m, Ar), 4.66
(0.1H, t, J 10.4, n-PhHCC), 4.38–4.36 (1.4H, m, b-PhHCC × 2),
3.96–3.84 (0.2H, m, n-PhHCC, n-COHCC), 3.83–3.81 (1.4H, m,
b-COHCC × 2), 3.78 (0.6H, s, d-OMe), 3.72 (4.2H, s, b-OMe ×
2), 3.70 (0.3H, s, n-OMe), 3.73–3.68 (1.0H, m, d-PhHCC × 2,
d-OMe), 3.47 (0.4H, m, d-COHCC × 2), 3.35–3.31 (0.1H, m, n-
COHCC), 3.27 (0.3H, s, n-OMe); dC (67.8 MHz, CDCl3) 172.9,
138.4, 128.9, 128.6, 128.5, 128.3, 128.1, 127.9, 127.7, 127.3, 127.12,
127.07, 126.8, 126.6, 125.4, 52.1, 51.9, 47.3, 46.8, 44.9, 44.6, 44.4,
43,3, 43.2, 29.7; HRMS (ESI) Found: 347.1264 [M + Na]+. Calc.
for C20H20O4Na 347.1260.
=
9.5, OH), 3.55 (3H, s, OMe); dC (67.8 MHz, CDCl3) 171.2 (C O),
=
170.9 (C O), 140.2, 130.8, 130.75, 129.8, 129.75, 129.69, 129.67,
126.51, 126.47, 122.4, 98.8 (C1), 72.0 (C2), 69.5 (C4), 59.2 (C3),
57.0 (C5), 56.1 (Me), 44.6 (cyclobutane), 44.5 (cyclobutane), 42.0
(cyclobutane), 42.0 (cyclobutane); HRMS (ESI) Found: 580.9770
[M + H]+. Calcd for C24H23O7Br2 580.9811.
Photoirradiation of compound 5d14 for 44 h. A solution of
compound 5d14 (47 mg, 0.107 mmol) in CHCl3 (5 mL), bubbled
with argon gas prior to the reaction, was irradiated for 44 h at
16 ◦C with a 500 W Hg(Xe) lamp (band-filtered at 313 nm).
After removal of the solvent, the residue was chromatographed
on silica-gel (toluene–ethyl acetate, 5 : 1) to give both isomers
of methyl b-D-xylopyranoside-2,4-b-truxinates-d14 7d14A (15 mg,
32%) and 7d14B (5 mg, 11%) as syrups and a fraction (Fr3; 15 mg,
32%) containing the mixture of methyl b-D-xylopyranoside-2,4-
truxinates-d14 (7d14).
Fr1 includes 7BrA and methyl b-D-xylopyranoside-2,4-b-3,3ꢀ-
dibromotruxinate (7BrB), in the ratio 0.83 : 0.17; Rf 0.20 (hexane–
ethyl acetate, 3 : 2); [a]D22 −36.6 (c 0.56 in CHCl3); dH (400 MHz,
CDCl3) 7.26–6.78 (8H, m, Ar), 5.11 (0.17H, s, 1-Hꢀ), 4.92 (0.83H, s,
1-H), 4.78–4.72 (2H, m, 2-H, 2-Hꢀ, 4-H, 4-Hꢀ), 4.64–4.61 (0.34H,
m, PhHꢀCC × 2), 4.54–4.41 (2.66 H, m, 3-H, 3-Hꢀ, PhHCC ×
2), 4.33–4.27 (1H, m, 5-Ha, 5-Hꢀa), 4.16 (0.17H, d, J5a,5b 13.8,
5-Hꢀb), 4.13–4.02 (1.66H, m, COHCC × 2), 3.90–3.79 (2.17H,
m, 5-Hb, COHꢀCC × 2, OH, OHꢀ), 3.56 (0.51H, s, OMeꢀ), 3.55
7d14A. [a]2D2 −37.9 (c 0.77 in CHCl3); dH (400 MHz, CDCl3) 4.93
(1H, s, 1-H), 4.77–4.74 (1H, m, 2-H, 4-H), 4.57–4.53 (1H, m, 3-H),
4.31 (1H, d, J5a,5b 13.4, 5-Ha), 3.89 (1H, d, J5a,5b 13.4, 5-Hb), 3.81
(1H, d, J3,OH 9.8, OH), 3.55 (3H, s, OMe); dC (67.8 MHz, CDCl3)
=
(2.49H, s, OMe); dC (67.8 MHz, CDCl3) 171.2 (C O), 170.9
=
=
(C O), 170.0 (C O), 130.8, 130.8, 130.8, 130.8, 129.9, 129.8,
129.7, 129.7, 129.7, 126.5, 126.5, 126.3, 126.1, 122.5, 122.4, 122.4,
98.8 (C1), 98.7 (C1ꢀ), 73.2 (C2ꢀ), 72.0 (C2), 70.0 (C4ꢀ), 69.5 (C4),
60.2 (C3ꢀ), 59.2 (C3), 57.0 (C5), 56.6 (C5ꢀ), 56.1 (Me), 56.1 (Meꢀ),
46.1 (cyclobutaneꢀ), 42.8 (cyclobutaneꢀ), 42.0 (cyclobutane), 42.0
(cyclobutane); HRMS (ESI) Found: 580.9818 [M + H]+. Calcd for
C24H23O7Br2 580.9811.
=
=
171.7 (C O), 171.4 (C O), 138.1, 127.8, 127.5, 127.1, 98.9 (C1),
71.8 (C2), 69.4 (C4), 59.2 (C3), 57.0 (C5), 56.1 (Me), 29.7 (m,
cyclobutane); HRMS (ESI) Found: 461.2286 [M + Na]+. Calc. for
C24H10D14O7Na 461.2298.
7d14B. [a]2D2 −65.0 (c 0.14 in CHCl3); dH (400 MHz, CDCl3)
5.07 (1H, s, 1-H), 4.72–4.70 (1H, m, 2-H), 4.70–4.69 (1H, m, 4-
H), 4.47–4.42 (1H, m, 3-H), 4.29 (1H, dd, J4,5a 1.2, J5a,5b 13.4,
5-Ha), 3.83 (1H, d, J5a,5b 13.4, 5-Hb), 3.83 (1H, d, J3,OH 9.9, OH),
Ester exchange reaction for methyl b-D-xylopyranoside-2,4-b-
3,3ꢀ-dibromotruxinates (7Br). A mixture of methyl b-D-xylo-
pyranoside-2,4-b-3-bromotruxinates (7Br: 65 mg, 0.112 mmol) in
Fr1 obtained in the previous section were treated with SOCl2–
MeOH (1 : 100, 5.0 mL) under argon gas for 15 h at room tem-
perature. After evaporation, the mixture was dissolved in CHCl3,
washed with sat. NaHCO3, dried over MgSO4, and evaporated.
The residue was chromatographed on silica-gel (hexane–ethyl
acetate, 2 : 1 to 3 : 2) to give b-3,3ꢀ-dibromotruxinate 8Brb (52 mg,
=
3.53 (3H, s, OMe); dC (67.8 MHz, CDCl3) 174.4 (C O), 170.2
=
(C O), 98.7 (C1), 73.0 (C2), 69.9 (C4), 60.2 (C3), 56.7 (C5),
56.1 (Me); HRMS (ESI) Found: 461.2296 [M + Na]+. Calc. for
C24H10D14O7Na 461.2298.
Fr3 includes methyl b-D-xylopyranoside-2,4-b-truxinate-d14
(7d14A), methyl b-D-xylopyranoside-2,4-d-truxinate-d14 (7d14C),
and methyl b-D-xylopyranoside-2,4-n-truxinate-d14 (7d14D), in the
ratio 0.5 : 0.25 : 0.25; [a]D22 −38.0 (c 0.76 in CHCl3); dH (400 MHz,
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97%) as a white solid: dH (400 MHz, CDCl3) 7.22 (1H, m, 4-H–
Ph), 7.09 (1H, t, J 1.6, 2-H–Ph), 7.00 (1H, t, J 7.9, 5-H–Ph), 6.81
(1H, m, 6-H–Ph), 4.35, 3.72 (2H, each m, cyclobutane), 3.76 (6H, s,
OMe × 2); dC (67.8 MHz, CDCl3) 172.4, 140.3, 130.7, 129.8, 129.7,
126.4, 122.3, 52.3, 44.5, 42.9; HRMS (ESI) Found: 502.9497 [M
+ Na]+. Calc. for C20H18O4Br2Na 502.9470.
5090; (b) T. Izumi, H. Hashimoto and H. Yuasa, Chem. Commun.,
2004, 94–95; (c) H. Yuasa, T. Izumi, N. Mitsuhashi, Y. Kajihara and
H. Hashimoto, Chem.–Eur. J., 2005, 11, 6478–6490.
3 (a) H. Yuasa, N. Miyagawa, T. Izumi, M. Nakatani, M. Izumi and H.
Hashimoto, Org. Lett., 2004, 6, 1489–1492; (b) H. Yuasa, N. Miyagawa,
M. Nakatani, M. Izumi and H. Hashimoto, Org. Biomol. Chem., 2004,
2, 3548–3556.
4 (a) B. S. Green, Y. Rabinsohn and M. Rejto, Carbohydr. Res., 1975,
45, 115–126; (b) S. Akabori, T. Kumagai, Y. Habata and S. Sato, Bull.
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T. Imae and Y. Sawaki, J. Chem. Soc., Perkin Trans. 2, 1994, 1003–1009.
5 The same reaction with allyloxide is reported: E. Petra´kova´ and P.
Kova´cˇ, Carbohydr. Res., 1982, 101, 141–147.
6 (a) J. D. Hung, M. Lahav, M. Luwisch and G. M. J. Schmidt,
Isr. J. Chem., 1972, 10, 585–599; (b) D. A. Ben-Efraim and B. S. Green,
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Acknowledgements
This work was supported by the Grant of the 21st Century
COE Program and a Grant-in-Aid for Scientific Research (no.
13680668) from the Japanese Ministry of Education, Culture,
Sports, Science and Technology. We thank Professor Yohji Nakat-
suji (Osaka Institute of Technology) for helpful discussions.
7 M. Kuzuya, M. Tanaka and T. Okuda, Tetrahedron Lett., 1983, 24,
4237–4240.
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The Royal Society of Chemistry 2006
©