The absolute configuration of the mushroom metabolites involutin and chamonixin

Article abstract of DOI:10.1016/S0040-4020(01)00761-X

The absolute configurations of the cyclopentanoid fungal metabolites involutin (1) and chamonixin (2) have been determined by application of the high-field ¹H NMR variant of Mosher's method. The experimental results are supported by quantum chemical calculations.

Full text of DOI:10.1016/S0040-4020(01)00761-X

TETRAHEDRON
Pergamon
Tetrahedron 57 -2001) 7857±7863
The absolute con®guration of the mushroom metabolites
involutin and chamonixin
a
Robert Feling, Kurt Polborn, Wolfgang Steglich, Jorg MuÈhlbacher and Gerhard Bringmann
a
a,p
b
b
È
a
È È
Department Chemie der Ludwig-Maximilians-Universitat, Butenandtstr. 5-13, Haus F, D-81377 Munchen, Germany
b
È
È
Institut fur Organische Chemie, Am Hubland, D-97074 Wurzburg, Germany
Dedicated to Professor Peter Welzel on the occasion of his 65th birthday
Received 11 June 2001; revised 23 July 2001; accepted 25 July 2001
AbstractÐThe absolute con®gurations of the cyclopentanoid fungal metabolites involutin -1) and chamonixin -2) have been determined by
application of the high-®eld 1H NMR variant of Mosher's method. The experimental results are supported by quantum chemical calculations.
q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
2,5-Diarylcyclopentenones are characteristic constituents
of certain mushrooms of the order Boletales -Basidio-
mycetes).1,2 Typical examples are -2)-involutin -1)3,4,5
and -1)-chamonixin -2),6 which are responsible for the
conspicuous brown and blue color reactions observed
when the fruit bodies of Paxillus involutus and Chamonixia
caespitosa are bruised. From the vicinal coupling constant
3J4H,5Hˆ7 Hz in the H NMR spectra of 1 and 2, a relative
1
2. Results and discussion
cis-con®guration of the substituents at the cyclopentane ring
can be assigned.3,4,6 The CD spectra of 1 and 2 are effec-
2.1. Determination of the absolute con®guration by
Mosher derivatization and NMR analysis
tively mirror images of one another,6 suggesting that the
compounds should be near-enantiomeric. In this publication
we describe the determination of the absolute con®gurations
of these cyclopentanoid fungal metabolites.
-2)-Involutin -1) was isolated from fresh or freeze-dried
fruit bodies of P. involutus by acetone extraction followed
by chromatography on acetylated polyamide. Its absolute
con®guration was determined by Kakisawa's7 high-®eld
NMR variant of Mosher's method. In order to achieve a
selective esteri®cation of the 4-OH group with methoxy-tri-
¯uoromethyl)phenylacetyl -MTPA) chloride,8 the phenolic
and enolic OH functions had to be ®rst protected as methyl
ethers. For this purpose, a solution of 1 in methanol was
Scheme 1. O-Methylation of -2)-involutin -1).
Keywords: involutin; chamonixin; basidiomycetes; natural products; stereochemistry; CD calculations.
Corresponding author. Tel.: 149-89-2180-7757; fax: 149-89-2180-7756; e-mail: wos@cup.uni-muenchen.de
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020-01)00761-X

7858
R. Feling et al. / Tetrahedron 57 72001) 7857±7863
Scheme 2. Synthesis of model compounds 7 and 8.
Figure 1. Crystal structures of 7 and 8.
treated with diazomethane in the presence of silica gel
-Scheme 1). Chromatographic separation of the reaction
products yielded two isomeric tetramethyl ethers, 3 and 4,
in a 2:1 ratio. These isomers exhibit a characteristic
chemical shift difference of the protons at C-4 and C-5. In
3 the signals of CH-OH) and CH-Ar) are close to each other
-d 4.57 and 4.51, respectively), whereas in isomer 4 they
exhibit a much larger difference in chemical shift -d 5.13
and 4.06, respectively). A similar effect is observed in the
1H NMR spectra of the related model compounds 7 and
8, which were obtained by cis-selective reduction of
3-hydroxy-2,5-diphenyl-2-cyclopentene-1,4-dione -5) with
sodium borohydride, followed by methylation of the
resulting product, 6, with diazomethane -Scheme 2). The
structures of 7 and 8 were con®rmed by X-ray crystal-
lography -Fig. 1).
Interestingly, the isomeric tetramethyl ethers 3 and 4 exhibit
opposite CD curves -Fig. 2) despite their joint synthetic
origin from 1. This phenomenon can be explained by the
assumption that 3 and 4 possess near-enantiomeric chromo-
phores, which, as shown below, was supported by quantum
chemical CD calculations. These calculations inde-
pendently con®rm the assignment of the absolute con®gu-
ration as determined by the modi®ed Mosher's method
mentioned above and detailed below.
2
For the preparation of the MTPA ester, alcohol 4 was
selected, since it contains protons on both sides nearby the
carbinol group, a necessary prerequisite for the application
of the high-®eld NMR variant of Mosher's method.9 Thus,
treatment of 4 with -S)- and -R)-MTPA chloride, DMAP,
and N-ethylmorpholine yielded the -R)- and -S)-MTPA
esters 9 and 10, respectively.
0
4
-2
3
-4
200
250
300
350
wavelength λ [nm]
Figure 2. CD spectra of involutin tetramethyl ethers 3 -Ð) and 4 -´´´) -in
MeOH).

R. Feling et al. / Tetrahedron 57 72001) 7857±7863
7859
shifts of the MTPA moiety caused by the reciprocal shield-
ing effect of the 3,4-dimethoxyphenyl residue.
Figure 3. DdR±S values determined from the MTPA esters 9 and 10.
Table 1. Temperature dependence of the shift differences DdR±S of MTPA
esters 9 and 10 -in CDCl3, 400 MHz)
The conformation of compounds 9 and 10 was con®rmed by
1H NMR experiments at different temperatures as proposed
by Riguera.11 The spectra of the diastereomeric MTPA esters
9 and 10 recorded at reduced temperatures exhibited increas-
ing shift differences in the expected directions -Table 1).
T -K) esters 9/10 -DdR±S
)
273
253
233
213
5-H
500H
10.034
10.182
10.112
10.066
10.141
10.030
20.393
10.045
10.086
20.214
10.040
10.198
10.131
10.098
10.161
10.057
20.434
10.049
10.095
20.259
10.050
10.218
±
10.060
10.220
±
600H
200H
o-H
±
±
In summary, the absolute con®guration of -2)-cis-involutin
-1) from P. involutus -Batsch: Fr.) Fr. was established as
-4S,5R). The -4R,5S) con®guration of -1)-chamonixin -2)
from C. caespitosa Roll. follows from its mirror-symmetri-
cal CD spectrum. The enantiomer of 2, -2)-chamonixin,12 is
present in P. involutus as a minor constituent and could be
isolated in 0.03% yield from lyophilised fruit bodies -see
Section 3).
10.219
10.069
20.475
10.059
10.106
20.309
10.265
10.073
20.519
10.081
10.116
20.369
m-H
3-OCH3
300-OCH3
400-OCH3
2000-OCH3
The shift differences DdR±S shown in Fig. 3 were determined
from the H NMR spectra of 9 and 10.
1
2.2. Con®gurational assignment by quantum chemical
CD calculation
From the sign of the DdR±S values and the assumption of a
`Mosher plane', the absolute con®guration of -2)-involutin
is -4S,5R).10 This assignment is supported by the proton
To explain the mirror-like CD curves of the isomeric
permethyl ethers 3 and 4 and to con®rm the con®gurational
4
4
calcd. for (4S,5R)-3
experimental
2
2
0
mlo]
]
/
0
-2
-4
2
2
[
[cm
experimental
-2
calcd. for (4R,5S)-3
-4
200
250
300
350
200
250
300
350
wavelength λ [nm]
wavelength λ [nm]
OH
O
OH
O
S
R
R
S
OCH3
OCH3
OCH3
OCH3
CH
O
CH
3
O
3
H3CO
H3CO
3
ent-3
Figure 4. Calculated CD spectra for 3 and ent-3 in comparison with the experimental one.

7860
R. Feling et al. / Tetrahedron 57 72001) 7857±7863
1
1
calcd. for (4R,5S)-4
calcd. for (4S,5R)-4
mol]
/oml]
/
0
2
2
0
[mc
[cm
experimental
experimental
-1
200
-1
200
250
300
350
250
300
350
wavelength λ [nm]
wavelength λ [nm]
OH
OH
H3CO
H3CO
S
R
R
S
OCH3
OCH3
OCH3
OCH3
O
O
H3CO
H3CO
4
ent-4
Figure 5. CD spectra calculated for 4 and ent-4 in comparison with the experimental one.
assignments of involutin -1) and chamonixin -2) derived
from analysis of the NMR spectra of the MTPA esters, we
have independently determined the absolute con®guration of
3 and 4 by quantum chemical calculations and comparison of
the calculated CD spectra with the experimental ones, a
valuable tool as shown by numerous previous examples.13,14
rotations: Perkin±Elmer 214. UV/Vis and CD: S.A. Jobin
Yvon CD-6-Dichrograph. IR: Bruker FTIR spectro-
photometer IFS 45 or IFS 48. NMR: Varian VXR-400S
and Bruker ARX 300 with solvent peak as internal reference
-CDCl3: dH 7.24, dC 77.0; CD3OD: dH 3.35, dC 49.0;
[D6]acetone: dH 2.04, dC 29.8). TLC: Silica gel Merck G
plates. Column chromatography: silica gel Merck 60;
acetylated polyamide Macherey±Nagel SC 6-Ac. HPLC
was carried out on a Waters Millenium equipped with two
Waters 510 pumps, a Waters 717 plus autosampler and a
photodiode array detector Waters 996. Analytical column:
Nucleosil 100 RP-18, 5 mm, 250£4 mm; preparative
column: Nucleosil 100 RP-18, 7 mm, 250£16mm, and
Merck LiChrosorb DIOL, 7 mm, 250£25 mm. Preparative
HPLC -RP-18), solvent system A: acetonitrile/water 1:91
0.1% TFA, solvent system B: acetonitrile; gradient 100% A
to 100% B within 60 min, ¯ow rate 6 mL/min. MS and
HRMS were performed on a Finnigan MAT 95 double
focusing mass spectrometer equipped with an EI ion source
operated at 70 eV.
Considering the molecular ¯exibility of the relevant
chromophores, the CD calculations were based on
molecular dynamics simulations using the Tripos force
®eld,15 arbitrarily starting with the -4S,5R)-enantiomer of
3 and the -4S,5R)-enantiomer of 4. The simulations were
performed for a total time period of 500 ps, recording the
structure every 0.5 ps for further calculations.
For the 1000 structures thus collected, single CD spectra
were calculated and then averaged arithmetically to give
theoretical overall spectra. In order to take into account
systematic shifts of the calculated CD spectra, a `UV correc-
tion' was carried out for each calculated spectrum as
introduced earlier.13 The good agreement between the
calculated overall CD spectrum for -4S,5R)-3 with the
experimental one of 3 -Fig. 4) and the overall CD spectrum
calculated for -4S,5R)-4 with the experimental one of 4
-Fig. 5) permits an accurate attribution of the absolute
con®guration of both, 3 and 4, as -4S,5R), despite their
mirror-image like experimental CD curves.
P. involutus was collected in autumn 1996and 1998 near
Regensburg, Bavaria, Germany.
3.2. Isolation of 02)-involutin and 02)-chamonixin
Fresh or frozen fruit bodies -34 g) of P. involutus were cut
and shaken for 20 h with a mixture of acetone -0.5 L), 2 M
HCl -5 mL) and ascorbic acid -0.3 g). After ®ltration, the
extract was concentrated under reduced pressure, and the
remaining brown aqueous phase was extracted with
petroleum ether -2£100 mL) and EtOAc -3£200 mL).
The combined EtOAc extracts were dried -Na2SO4) and
3. Experimental
3.1. General
Melting points -uncorrected): Reichert Thermovar. Optical

R. Feling et al. / Tetrahedron 57 72001) 7857±7863
7861
25
concentrated under reduced pressure. The residue -0.2 g,
0.6%) was chromatographed on acetylated polyamide
-column 400£30 mm, acetone/MeOH 3:1) to yield 1
-35 mg, 0.1%) as a pale brown solid. According to HPLC,
the material was 95% pure and could be further puri®ed by
preparative HPLC on DIOL-phase -elution with n-hexane/
t-BuOMe 9:1, t-BuOMe/i-PrOH 1:9) or on RP-18 -elution
with acetonitrile/water/0.1% TFA). In the same manner, 1
-450 mg, 1%) and -2)-2 -15 mg, 0.03%) were obtained
from 45 g of lyophilised fruit bodies [HPLC on RP-18, 1:
tRˆ11 min, -2)-2: tRˆ14 min].
yellow oil; Rf 0.32 -CHCl3/MeOH, 30:1); [a]D ˆ119 -c
1.6, 96% EtOH); UV/Vis -MeOH): lmax -log e) 230 nm -sh,
2.61), 250, 285 -sh, 2.35); CD -MeOH, 0.4 mg/mL): lmax
-De) 320 nm -20.3), 284 -11.3), 251 -20.7), 231 -10.2);
IR -KBr): 3425 -br.), 2935, 2838, 1689, 1600 -s), 1513 -ss),
1463, 1420, 1353, 1251 -s), 1176, 1142, 1026, 837, 810,
767, 574 cm21; H NMR -300 MHz, CDCl3): d 3.83, 3.85
1
-each s, 2 OCH3, 6H), 4.51 -d, 3Jˆ7.2 Hz, 1H, 4-H), 4.57 -d,
3Jˆ7.2 Hz, 1H, 5-H), 6.68 -d, 4Jˆ2.1 Hz, 1H), 6.72 -dd, 3Jˆ
8.4 Hz, 4Jˆ2.1 Hz, 1H), 6.84 -d, 3Jˆ8.4 Hz, 1H), 6.94, 7.83
-each d, Jˆ8.7 Hz, 2H); 13C NMR -75 MHz, CDCl3): d
3
48.8 -C3±OCH3), 55.2 -C300 ±OCH3), 55.8/55.9 -C40 ±
OCH3/C400 ±OCH3), 57.5 -C-4), 74.1 -C-5), 111.6-CH),
111.7 -C-2), 113.6-2 CH), 116.6-C), 120.7 -C), 122.3
-CH), 126.6 -CH), 129.4 -CH), 148.9/149.5 -C-40/C-400),
158.8 -C-300), 179.8 -C-3), 203.4 -C-1); MS -EI): m/z -%)
370 -100) [M1], 341 -28), 325 -9), 281 -12), 267 -6), 233
-15), 191 -7), 165 -10), 119 -6); HRMS -EI): m/z 370.1411
-370.1416calcd for C 21H22O6).
3.2.1. 02)-Involutin [02)-1]. Mp 172±1748C -dec)., Lit.3
171±1748C; Rf 0.1 -toluene/ethyl formate/formic acid
25
10:5:3), brown spot with K3[Fe-CN)6]/NaHCO3); [a]D
ˆ
223 -c 1, 96% EtOH), Lit.3 223; UV/Vis -MeOH): lmax
-log e) 258.5 nm -4.39), 270.5 -4.38); IR -KBr): 3300 -br.),
2500, 1672, 1631, 1606, 1518, 1452, 1390, 1290, 1271,
1251, 1217, 1200, 1174, 1122, 1103, 1035, 960, 932, 897,
882, 843, 804, 777, 748 cm21; 1H NMR -300 MHz, CD3OD,
290 K): d 3.98 -d, 3Jˆ6.9 Hz, 1H, 5-H), 4.70 -d, 3Jˆ6.9 Hz,
3.3.2. 02)-cis-4-Hydroxy-3-methoxy-2-04-methoxyphenyl)-
5-03,4-dimethoxyphenyl)-2-cyclopenten-1-one 04). Pale
3
4
1H, 4-H), 5.52 -dd, Jˆ8.1 Hz, Jˆ2.0 Hz, 1H), 6.61 -d,
3
3
4Jˆ2.0 Hz, 1H), 6.78 -d, Jˆ9.0 Hz, 2H), 6.72 -d, Jˆ
25
yellow oil; Rf 0.41 -CHCl3/MeOH, 30:1); [a]D ˆ226- c
8.1 Hz, 1H), 7.71 -d, Jˆ9.0 Hz, 2H); 13C NMR -75 MHz,
3
0.5, 96% EtOH); UV/Vis -MeOH): lmax -log e)ˆ232 nm
-sh, 2.31), 250, 280 -sh, 2.17); CD -MeOH, 0.2 mg/mL):
lmax -De)ˆ320 nm -10.4), 277 -20.5), 251 -20.3), 227
-20.9), 212 -20.2); IR -KBr): 3435 -br.), 2934, 2838,
1686, 1603 -s), 1514 -ss), 1463, 1421, 1349, 1252 -s),
CD3OD, 290 K): d 58.3 -C-5), 68.7 -C-4), 115.7 -CH),
116.2 -CH), 118.0 -CH), 122.9 -CH), 123.6 -C), 128.5
-C), 130.6-CH), 145.7, 146.1, 157.4 -each C), signals for
C-1, C-2 and C-3 not visible; MS -EI): m/z -%)ˆ314 -1)
[M1], 296 -100), 163 -56), 134 -30), 106 -10); Anal. calcd
for C17H14O6: C, 64.97; H, 4.49. Found: C, 64.70; H, 4.60.
1170, 1143, 1025 -s), 838, 810, 766, 569 cm21; H NMR
1
-300 MHz, CDCl3): d 3.82, 3.84, 3.86, 4.20 -each s, 3H,
3
OCH3), 4.06-d, 3Jˆ6.6 Hz, 1H, 5-H), 5.13 -d, Jˆ6.6 Hz,
4
3
3.2.2. 02)-Chamonixin [02)-2]. Mp .1308C -dec)., Rf 0.2
-toluene/ethyl formate/formic acid 10:5:3, blue spot with
1H, 4-H), 6.71 -d, Jˆ1.8 Hz, 1H), 6.74 -dd, Jˆ8.1 Hz,
4Jˆ1.8 Hz, 1H), 6.86 -d, 3Jˆ8.1 Hz, 1H), 6.93 -d, Jˆ
3
25
8.7 Hz, 2H), 7.79 -d, Jˆ8.7 Hz, 2H); 13C NMR -75 MHz,
3
aqueous K3[Fe-CN)6]/NaHCO3); [a]D ˆ228 -c 1, 96%
EtOH), Lit.12 228.7; UV/Vis -MeOH): lmax -log e)
228 nm -4.27), 245 -4.29), 275 -sh, 4.14); IR -KBr):
3430±3330 -br.), 2930, 1682, 1607, 1516, 1444, 1368,
CDCl3): d 55.2, 55.9 -2£) -each OCH3), 56.5 -C-5), 58.2
-C1±OCH3), 67.5 -C-4), 111.6 -C-2), 113.5 -3£CH), 119.3,
122.3 -each C), 122.5, 126.1 -each CH), 129.9 -2£CH),
148.9, 149.3, 158.9 -each C), 180.0 -C-3), 200.7 -C-1);
MS -EI): m/z -%)ˆ370 -100) [M1], 338 -18), 325 -37),
324 -33), 310 -10), 294 -12), 262 -28), 191 -18), 151 -14);
HRMS -EI): m/zˆ370.1410 -370.1416calcd for C 21H22O6).
1344, 1249, 1228, 1174, 1004, 836cm 21
;
1H NMR
3
-300 MHz, CD3OD, 290 K): d 4.07 -d, Jˆ6.7 Hz, 1H, 5-
H), 4.78 -d, 3Jˆ6.7 Hz, 1H, 4-H), 6.78 -d, 3Jˆ8.7 Hz, 2H),
3
3
6.83 -d, Jˆ9.0 Hz, 2H), 7.03 -d, Jˆ8.7 Hz, 2H), 7.75 -d,
3Jˆ9.0 Hz, 2H); 13C NMR -75 MHz, CD3OD, 290 K): d
56.0 -C-5), 72.6 -C-4), 116.0 -CH), 116.4 -CH), 117.1
-C-2), 123.7 -C), 128.2 -C), 130.9 -CH), 132.5 -CH),
157.7, 157.9 -each C), 163.6 -C-3), 195.11 -C-1); MS
-EI): m/z -%)ˆ298 -3) [M1], 280 -51), 252 -4), 224 -4),
147 -100), 134 -13), 119 -11), 107 -6), 91 -6); HRMS
-EI):): m/z 298.0836-298.0841 calcd for C 17H14O5).
3.3.3. 0^)-cis-3,4-Dihydroxy-2,5-diphenyl-2-cyclopenten-
1-one 06). To a suspension of NaBH4 -0.38 g, 10 mmol) in
50 mL of anhydrous EtOH in a dried Schlenk apparatus
under argon were slowly added 0.36mL -20 mmol) of
water in dry EtOH -5 mL). The suspension was homo-
genized in an ultrasound bath, re¯uxed for 30 min and
then cooled to 08C. The resulting solution was then added
dropwise at 08C to a stirred solution of 3-hydroxy-2,5-
diphenyl-2-cyclopentene-1,4-dione -5)16 -1.32 g, 5 mmol)
in EtOH -50 mL). The formation of 6 was monitored by
TLC -Rf 0.34, toluene/ethyl formate/formic acid, 10:5:3).
After completion -ca. 30 min), acetic acid -10 mL) was
added and the mixture hydrolyzed with ice-cooled 2 M
HCl. The solution was concentrated, and the aqueous resi-
due was extracted with Et2O -3£15 mL). The combined
organic phases were dried -MgSO4) and concentrated
under reduced pressure to yield a light yellow oil.
Compound 6 was obtained as a colorless powder -1.20 g,
90%) on recrystallization from EtOAc/petroleum ether. Mp
.1908C -dec.); 1H NMR -300 MHz, [D6]acetone, 290 K): d
4.10 -br., 1H, 5-H), 4.90 -br., 1H, 4-H), 7.14±7.26-m, 6H),
3.3. Methylation of 02)-involutin
A stirred solution of 1 -200 mg, 0.64 mmol) in 96% MeOH
-5 mL) and silica gel -20 mg) was slowly titrated at 08C with
a freshly prepared solution of diazomethane in Et2O until no
more gas evolution was observed. The mixture was allowed
to warm to room temperature and, after the addition of a
small excess of CH2N2/Et2O, was stirred for 20 h. After
evaporation, the crude brown oil was separated by ¯ash
chromatography on silica gel -CHCl3/MeOH 30:1) to
yield the ethers 3 -52 mg, 25%) and 4 -28 mg, 12%).
3.3.1. 01)-cis-5-Hydroxy-3-methoxy-2-04-methoxyphenyl)-
4-03,4-dimethoxyphenyl)-2-cyclopenten-1-one 03). Pale

7862
R. Feling et al. / Tetrahedron 57 72001) 7857±7863
7.33±7.38 -m, 2H), 7.99 -m, 2H); 13C NMR -75 MHz,
[D6]acetone, 290 K): d 55.0, 71.0, 115.0, 126.7, 126.8,
127.8, 127.9, 128.1, 128.5, 128.6, 130.1, 131.4, 136.5; MS
-EI): m/z -%) 266 -M1, 34), 248 -100); C17H14O3 -266.3).
TLC -silica gel, Merck, 0.25 mm, petroleum ether/EtOAc
4:1) yielded the diastereomeric -R)- or -S)-MTPA esters, 9
-9 mg, 50%) and 10 -12 mg, 60%) respectively, as yellow
oils.
3.5.1. 0R)-MTPA ester 9. Yellow oil; Rf 0.15 -CHCl3/
MeOH, 30:1); UV/Vis -MeOH): lmax 204 nm -sh), 232
-sh), 278 -sh); H NMR -400 MHz, CDCl3): d 3.04 -q,
3.4. Methylation of 6
1
The alcohol 6 -1.06g, 4 mmol) was dissolved in 96%
MeOH -5 mL) and treated at 08C with a ®ve-fold excess
of an etheric diazomethane solution. The mixture was
stirred for 10 min and then treated with a few drops of acetic
acid. Evaporation of the solvent yielded the crude product in
form of an amorphous, yellowish solid. Chromatography on
silica gel -petroleum ether/EtOAc 2:1) yielded 8 -0.45 g,
40%), followed by 7 -0.56g, 50% ). 8 could also obtained
as a ®rst fraction by fractional crystallisation of the mixture
from petroleum ether/EtOAc -4:1). Both products 7 and 8
were diastereomerically pure -de.99%).
Jˆ1.1 Hz, through-space H±F coupling, 3H, C2000 ±OCH3),
3.60 -s, 3H,C3±OCH3), 3.77 -s, 3H, C300 ±OCH3), 3.82 -s,
3
3H, C40 ±OCH3), 3.83 -s, 3H, C400 ±OCH3), 4.24 -d, Jˆ
3
7.2 Hz, 1H, 5-H), 6.36 -d, Jˆ7.2 Hz, 1H, 4-H), 6.66 -d,
4
3
4
00
Jˆ1.6Hz, 1H, 2 -H), 6.74 -dd, Jˆ8.4 Hz, Jˆ1.6Hz,
3
3
1H, 600-H), 6.75 -d, Jˆ8.4 Hz, 1H, 500-H), 6.93 -d, Jˆ
8.8 Hz, 2H, 30,50-H), 7.12 -d, 3Jˆ8.0 Hz, 2H, o-Ph-H),
3
3
7.25 -dd, Jˆ8.0 Hz, Jˆ7.6Hz, 2H, m-Ph-H), 7.32 -dd,
3Jˆ7.6Hz, 4Jˆ1.2 Hz, 1H, p-Ph-H), 7.60 -2H, d, 3Jˆ
8.8 Hz, 20,60-H); 13C NMR -100 MHz, CDCl3): d 54.8
-OCH3), 55.0 -C-5), 55.3, 56.0, 55.7, 58.7 -each OCH3),
71.8 -C-4), 111.4 -CH), 113.6-2 £CH), 113.7 -CH), 121.7
-C), 122.3 -C), 122.9 -CH), 126.0 -C), 127.3, 128.2, 129.6
-each CH), 131.3 -C), 130.5 -2£CH), 148.8/149.0 -C-40/
C-400), 159.5 -C-300), 166.0 -COO), 175.1 -C-3), 199.8
-C-1); MS -EI): m/z -%) 586-7) [M 1], 542 -7), 510 -7),
384 -10), 368 -11), 354 -33), 353 -92), 352 -100), 337
-29), 293 -12), 281 -17), 189 -61), 175 -20), 170 -28), 165
-19), 147 -11), 135 -19), 119 -16), 105 -28), 91 -14), 77 -21),
44 -12); HRMS -EI): m/z 586.1802 -586.1814 calcd for
C31H29F3O8).
3.4.1. 0^)-cis-5-Hydroxy-3-methoxy-2,4-diphenyl-2-cyclo-
penten-1-one 07). Mp 158±1618C; Rf 0.41 -petroleum ether/
EtOAc, 4:1); UV/Vis -MeOH): lmax -log e) 202.5 nm
-4.18), 249.3 -3.86); IR -KBr): 3399 -br.), 3026, 2954,
1677 -s), 1591 -s), 1362 -s), 1136, 1052, 711, 700 cm21
;
1H NMR -300 MHz, [D6]acetone): d 3.88 -s, 3H, OCH3),
4.15 -d, 3Jˆ7.1 Hz, 1H, 4-H), 4.63 -d, 3Jˆ 3.0 Hz, 1H, OH),
3
3
4.82 -dd, Jˆ7.2 Hz, Jˆ3.0 Hz, 1H, 5-H), 7.31±7.38 -m,
8H), 7.89±7.92 -m, 2H); 13C NMR -75 MHz, [D6]acetone):
d 50.2 -C-4), 58.3 -OCH3), 75.5 -C-5), 119.4 -C-2), 128.1,
128.6, 129.0, 129.5, 129.9, 130.5 -each CH), 132.4, 137.3
-each C), 182.6-C-3), 203.5 -C-1); MS -EI): m/z -%)
280 -100) [M1], 251 -16), 234 -14), 220 -9), 191 -25),
185 -6), 178 -5), 131 -7), 105 -6), 91 -8), 89 -9); Anal.
calcd for C18H16O3: C, 77.12; H, 5.75. Found: C, 77.52;
H, 5.89.
3.5.2. 0S)-MTPA ester 10. Yellow oil; Rf 0.19 -CHCl3/
MeOH, 30:1); UV/Vis -MeOH): lmax 204 nm -sh), 232
-sh), 278 -sh); H NMR -400 MHz, CDCl3): d 3.21 -q,
1
Jˆ1.0 Hz, through-space H±F coupling, 3H, C2000 ±OCH3),
00
3.74 -s, 3H, C300 ±OCH3), 3.76-s, 3H, C4 ±OCH3), 3.83 -s,
3
3H, C40 ±OCH3), 3.95 -s, 3H, C3±OCH3), 4.21 -d, Jˆ
3
7.2 Hz, 1H, 5-H), 6.39 -d, Jˆ7.2 Hz, 1H, 4-H), 6.59 -d,
3.4.2. 0^)-cis-4-Hydroxy-3-methoxy-2,5-diphenyl-2-cyclo-
penten-1-one 08). Mp 142±1448C; Rf 0.53 -petroleum ether/
EtOAc, 4:1); UV/Vis -MeOH): lmax -log e) 202.5 nm
-4.18), 249.3 -3.86); IR -KBr): 3378 -br.), 3031, 2961,
1659 -s), 1614 -s), 1593 -s), 1494 -s), 1358 -s), 1238 -s),
3Jˆ8.4 Hz, 1H, 500-H), 6.61 -d, Jˆ1.8 Hz, 1H, 200-H),
4
3
4
3
6.65 -dd, Jˆ8.4 Hz, Jˆ1.8 Hz, 1H, 600-H), 6.94 -d, Jˆ
8.8 Hz, 2H, 30,50-H), 7.01 -d, 3Jˆ8.0 Hz, 2H, o-Ph-H),
3
3
7.23 -dd, Jˆ7.2 Hz, Jˆ8.0 Hz, 2H, m-Ph-H), 7.33 -dd,
3Jˆ7.2 Hz, Jˆ1.2 Hz, 1H, p-Ph-H), 7.67 -d, Jˆ8.8 Hz,
2H, 20,60-H); 13C NMR -100 MHz, CDCl3): dˆ55.0
-OCH3), 55.1 -C-5), 55.3 -OCH3), 55.7 -2£OCH3), 58.8
-OCH3), 71.5 -C-4), 111.0 -CH), 113.7 -2£CH), 121.6
-C), 121.8 -C), 122.2 -C), 122.9 -CH), 124.4 -C), 125.5
-C), 127.4 -CH), 127.6-C), 128.3 -CH), 128.6-C), 129.6
-CH), 130.2 -C), 130.4 -2£CH), 148.8/148.7 -C-40/C-400),
159.5 -C-300), 166.0 -COO), 175.0 -C-3), 199.9 -C-1); MS
-EI): m/z -%) 586-7) [M 1], 510 -9), 368 -7), 354 -61), 352
-60), 337 -14), 293 -10), 281 -19), 207 -16), 189 -50), 170
-40), 149 -16), 119 -34), 105 -100), 91 -30), 77 -92), 58 -23),
51 -25); HRMS -EI): m/z 586.1812 -586.1814 calcd for
C31H29F3O8).
4
3
1047, 949, 711, 700 cm21 -s); H NMR -300 MHz, [D6]-
1
3
acetone): d 4.04 -d, Jˆ6.6 Hz, 1H, 5-H), 4.25 -s, 3H,
3
OCH3), 5.41 -d, Jˆ6.6 Hz, 1H, 4-H), 7.21±7.38 -m, 8H),
7.84±7.87 -m, 2H); 13C NMR -75 MHz, [D6]acetone): d
58.5 -OCH3), 58.7 -C-5), 68.6 -C-4), 119.4 -C-2), 127.9,
128.2, 128.9, 129.0, 129.8, 132.4 -each CH.), 132.5, 137.5
-each C), 183.0 -C-3), 202.0 -C-1); MS -EI): m/z -%) 280
-31) [M1], 262 -7), 248 -11), 234 -100), 220 -19), 203 -25),
191 -19), 185 -21), 131 -20), 118 -8), 91 -17), 89 -17); Anal.
calcd for C18H16O3: C, 77.12; H, 5.75. Found: C, 77.70; H,
5.84.
3.5. Preparation of the MTPA esters 9 and 10
To a solution of 4 -12.0 mg, 0.03 mmol) in anhydrous
CH2Cl2 -3 mL) was added at 08C N-ethylmorpholine
-6.8 mg, 2.0 equiv.) and catalytic amounts of DMAP
-0.5 mg). After the addition of -S)- or -R)-MTPA chloride
-14.4 mg, 0.06mmol), the solution was warmed to room
temperature and stirred for 12 h. The reaction mixture was
hydrolysed with saturated NH4Cl solution, washed with
cold 2 M HCl, aqueous NaHCO3 and water. Preparative
3.6. X-Ray analyses
3.6.1. Crystal data for 7. C18H16O3, Mˆ280.31, mono-
Ê
Ê
clinic, space group P21/n, aˆ10.345-2) A, bˆ8.952-2) A,
Ê
Ê 3
cˆ16.106-5) A, bˆ105.98-2)8, Vˆ1433.9-6) A , Zˆ4,
Dcˆ1.298 Mg/m3, mˆ0.088 mm21
, crystal dimensions
0.37£0.43£0.53 mm3, F-000)ˆ592, Tˆ295-2) K, uˆ
3.06±23.978, re¯ections measured 2335, unique re¯ections

R. Feling et al. / Tetrahedron 57 72001) 7857±7863
7863
2246, Rintˆ0.0103, min. and max. transmission coef®cient
0.9594, 0.9988, R1ˆ0.0490 and wR2ˆ0.1080 for all 1622
observed re¯ections with I.2s-I), R1ˆ0.0711 and wR2ˆ
0.1208 for all re¯ections and 191 parameters. Final electron
density 0.199 and 20.195 e/A ; Sˆ1.103.
Colorado) for providing the program package BDZDO/
MCDSPD, and Dr K.-P. Gulden for porting it to Linux.
Ê 3
References
1. Gill, M.; Steglich, W. Prog. Chem. Org. Natl. Prod. 1987, 51,
1±317.
3.6.2. Crystal data for 8. C18H16O3, Mˆ280.31, mono-
Ê
Ê
clinic, space group P21/c, aˆ10.293-5) A, bˆ10.084-2) A,
Ê
Ê 3
2. Besl, H.; Dorsch, R.; Fischer, M. Zeitschr. f. Mykol. 1996, 62,
195±199.
cˆ13.802-5) A, bˆ97.56-3)8, Vˆ1420.1-9) A , Zˆ4, Dcˆ
1.311 Mg/m3, mˆ0.089 mm21, crystal dimensions: 0.33£
0.40£0.53 mm3, F-000)ˆ592, Tˆ295-2) K, uˆ2.51±
24.978, re¯ections measured 2605, unique re¯ections
2491, Rintˆ0.0181, min. and max. transmission coef®cient
0.9206, 0.9992, R1ˆ0.0414 and wR2ˆ0.1004 for all 1981
observed re¯ections with I.2s-I), R1ˆ0.0556and wR2ˆ
0.1101 for all re¯ections and 192 parameters. Final electron
3. Edwards, R. L.; Elsworthy, G. C.; Kale, N. J. Chem. Soc. C
1967, 405±409.
4. Edwards, R. L.; Gill, M. J. Chem. Soc., Perkin Trans. 1 1973,
1529±1537.
5. Besl, H.; Bresinsky, A.; Steglich, W.; Zipfel, K. Chem. Ber.
1973, 106, 3223±3229.
Ê 3
6. Steglich, W.; Thilmann, A.; Besl, H.; Bresinsky, A.
Z. Naturforsch. 1977, 32c, 46±48.
density 0.121 and 20.165 e/A , Sˆ1.100.
7. -a) Ohtani, I.; Kusumi, T.; Ishitsuka, M. O.; Kakisawa, H.
Tetrahedron Lett. 1989, 30, 3147±3150. -b) Ohtani, I.;
Kusumi, T.; Ishitsuka, M. O.; Kakisawa, H. J. Am. Chem.
Soc. 1991, 113, 4092±4096.
For the compounds 7 and 8 the data were collected on a
Nonius MACH3 kappa diffractometer with MoKa radiation
Ê
-lˆ0.71073 A). The structures were solved by direct
methods using SHELXS-8617 and re®ned by full matrix
least squares on F2 by SHELXL-93.18 The molecular
views were realised by ZORTEP.19
8. -a) Dale, J. A.; Dull, D. L.; Mosher, H. S. J. Org. Chem. 1969,
34, 2543±2549. -b) Dale, J. A.; Mosher, H. S. J. Am. Chem.
Soc. 1973, 95, 512±519.
Â
9. Seco, J. M.; QuinÄoa, E.; Riguera, R. Tetrahedron: Asymmetry
2000, 11, 2781±2791.
Crystal and data collection parameters, relevant structure
re®nement parameters, atomic coordinates for the non-
hydrogen atoms, positional and isotropic displacement co-
ef®cients for hydrogen atoms, a list of anisotropic displace-
ment coef®cients for the non-hydrogen atoms and a full
list of bond distances and bond angles have been deposited
with the Cambridge Crystallographic Data Center. The
crystallographic data will be sent on quoting the
CCDC numbers 163731 for 7 and 163730 for 8 -e-mail:
deposit@ccdc.cam.ac.uk).
10. The description -4S,5R)-involutin relates to the tautomer
given in formula 1. NMR measurements in CD3OD indicate
that at room temperature 1 and 2 are in a rapid equilibrium
with their vinylogous acid tautomer [CvO and vC-OH)
interchanged].
Â
11. Latypov, S. K.; Seco, J. M.; QuinÄoa, E.; Riguera, R. J. Am.
Chem. Soc. 1998, 120, 877±882.
12. Besl, H.; Bresinsky, A.; Herrmann, R.; Steglich, W.
Z. Naturforsch. 1980, 35c, 824±825.
13. Bringmann, G.; Busemann, S. In Natural Product Analysis,
Schreier, P., Herderich, M., Humpf, H. U., Schwab, W., Eds.;
Vieweg: Wiesbaden, 1998; pp 195±212.
3.7. Computational details
3.7.1. Molecular dynamics 0MD). The MD simulations
were performed on Silicon Graphics Octane -R10000)
workstations using the Tripos15 force ®eld as implemented
in the molecular modeling package Sybyl.15 The molecules
were weakly coupled to a thermal bath at Tˆ400 K,20 with a
temperature relaxation time of tˆ0.1 ps.
14. Dreyer, M.; Nugroho, B. W.; Bohnenstengel, F. I.; Wray, V.;
Witte, L.; Bringmann, G.; MuÈhlbacher, J.; Herold, M.; Hung,
P. D.; Kiet, L. C.; Proksch, P. J. Natl. Prod. 2001, 64, 415±
420.
15. SYBYL: Tripos Associates, 1699 Hanley Road, Suite 303,
St. Louis, MO 63144, USA.
16. -a) Claisen, L.; Ewan, Th. Liebigs Ann. Chem. 1895, 284,
245±299. -b) Ruggli, P.; Schmidlin, J. Helv. Chim. Acta
1944, 27, 499±502.
3.7.2. CD calculations. The wave functions for the calcula-
tion of the rotational strength for the electronic transitions
from the ground state to excited states were obtained by a
CNDO/S-CI21,22 calculation, in which the CI expansion21,22
takes into account the ground state and all n and p orbitals.
These calculations were carried out on Linux iPII work-
stations using the BDZDO/MCDSPD21 program package.
For a better comparison of the theoretical CD spectrum
with the experimental one, a Gaussian band shape function
was generated over the calculated rotational strength values.
17. Sheldrick, G. M. SHELXS-86, Program for Crystal Structure
È
È
Solution; Universitat Gottingen, 1986.
18. Sheldrick, G. M. SHELXL-93; Program for Crystal Structure
È
È
Solution; Universitat Gottingen, 1993.
19. Zsolnai, L.; Huttner, G. ZORTEP; Universitat Heidelberg,
1994.
È
20. Berendsen, H. J. C.; Postma, J. P. M.; van Gunsteren, W. F.;
DiNola, A.; Haak, J. R. J. Chem. Phys. 1984, 81, 3684±3690.
21. Downing, J. W. Program package BDZDO/MCDSPD,
Department of Chemistry and Biochemistry, University of
Colorado, Boulder, USA; modi®ed by Fleischhauer, J.;
Schleker, W.; Kramer, B.; ported to Linux by Gulden, K.-P.
Acknowledgements
We thank the Fonds der Chemischen Industrie for ®nancial
support, Professor J. Fleischhauer -University of Aachen),
Professor J. Michl, and J. W. Downing -University of
Â
22. Del Bene, J.; Jaffe, H. H. J. Chem. Phys. 1968, 48, 1807±1813.