α,β-Dibenzyl-γ-butyrolactone lignan alcohols: total sytnhesis of (+/-)-7'-hydroxyenterolactone, (+/-)-7'-hydroxymatairesinol and (+/-)-8-hydroxyenterolactone

Article abstract of DOI:10.1016/S0039-128X(01)00107-6

Two trans-α,β-dibenzyl-γ-butyrolactone lignans carrying a hydroxyl group at the β-benzylic carbon aton and a α-hydroxy α,β-dibenzyl-γ-butyrolactone lignan were synthesized in racemic form using the tandem conjugate addition reaction to construct the basic lignan skeleton. Subsequent reaction steps involved either a catalytic reduction of the regenerted keto group to the alcohol, or a hydrogenolysis to benzylic methylene followed by lactone enolate formation and oxidation to give the α-hydroxybutyrolactones. These procedures were applied for the synthesis of 7'-hydroxyenterolactones and 7'-hydroxymatairesinols, and 8-hydroxyenterolacotones, respectively. The diastereomeric mixtures of these compounds were separated either by HPLC techniques or column chromatography and the structures were elucidated using NMR spectroscopy.

Full text of DOI:10.1016/S0039-128X(01)00107-6

Steroids 66 (2001) 777–784
␣,␤-Dibenzyl-␥-butyrolactone lignan alcohols: total synthesis of (Ϯ)-7Ј-
hydroxyenterolactone, (Ϯ)-7Ј-hydroxymatairesinol and (Ϯ)-8-
hydroxyenterolactone
Taru H. Ma¨kela¨*, Seppo A. Kaltia, Kristiina T. Wa¨ha¨la¨, Tapio A. Hase
Organic Chemistry Laboratory, Department of Chemistry, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 University of Helsinki, Finland
Received 14 November 2000; accepted 19 January 2001
Abstract
Two trans-␣,␤-dibenzyl-␥-butyrolactone lignans carrying a hydroxyl group at the ␤-benzylic carbon atom and a ␣-hydroxy ␣,␤-
dibenzyl-␥-butyrolactone lignan were synthesized in racemic form using the tandem conjugate addition reaction to construct the basic lignan
skeleton. Subsequent reaction steps involved either a catalytic reduction of the regenerated keto group to the alcohol, or a hydrogenolysis
to benzylic methylene followed by lactone enolate formation and oxidation to give the ␣-hydroxybutyrolactones. These procedures were
applied for the synthesis of 7Ј-hydroxyenterolactones and 7Ј-hydroxymatairesinols, and 8-hydroxyenterolactones, respectively. The diaste-
reomeric mixtures of these compounds were separated either by HPLC techniques or column chromatography and the structures were
elucidated using NMR spectroscopy. © 2001 Elsevier Science Inc. All rights reserved.
Keywords: Lignans; Lactones; Alcohols; Michael reactions; Synthesis
1. Introduction
troscopy and molecular modelling [10]. Hydroxymataires-
inol has been identified from this tree as an inhibitor against
the growth of the fungus F. annosus [11], whereas (Ϫ)-
parabenzlactone is one of the insect feeding inhibitors found
in Parabenzoin trilobum Nakai [3].
Only a few trans-␣,␤-dibenzyl-␥-butyrolactone lignans,
carrying a hydroxyl group at a benzylic position, are known
in nature. These are hydroxymatairesinol 1a and its isomer
allohydroxymatairesinol 2a [1,2], (Ϫ)-parabenzlactone 1b
[3,4], and hydroxyarctigenin 2c [5]. The corresponding ox-
idation products, the oxo-compounds 3a and 3b, are also
naturally occurring [1,6]. The derivatives of matairesinol
occur frequently in various plants, especially trees, which
makes them possible intermediates in lignin biosynthesis
[7].
Kawamura et al. [8,9] established the main constituents
causing photodiscoloration in sapwood of Western hemlock
(Tsuga heterophylla) to be hydroxymatairesinol 1a, allohy-
droxymatairesinol 2a and oxomatairesinol 3a. They also
investigated the chemical reaction mechanisms responsible
for the onset of photodiscoloration.
Hydroxymatairesinol 1a and its isomer 2a were isolated
from the heartwood of Norway spruce (Picea abies) as a
mixture, and their structures were elucidated by NMR spec-
* Corresponding author. Tel.: ϩ358-9-19150392; fax: ϩ358-9-
19150366.
E-mail address: taru.makela@helsinki.fi (T.H. Ma¨kela¨).
0039-128X/01/$ – see front matter © 2001 Elsevier Science Inc. All rights reserved.
PII: S0039-128X(01)00107-6

778
T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
Natural lignans of the ␣,␤-dibenzyl-␥-butyrolactone se-
lignan, 7Ј-hydroxyenterolactone 1d and/or 2d, has been
detected and tentatively identified in human urine, together
with two isomeric hydroxymatairesinols 1a and 2a [37,38].
The latter are well known plant constituents and may thus
be precursors of the new mammalian lignan.
ries, carrying a hydroxyl group ␣ to the carbonyl group, are
widely distributed in plants [12]. The antileukemic action of
wikstromol/(ϩ)-nortrachelogenin 4a isolated from Wikstro-
emia viridiflora [13], and anti-HIV and cytostatic activity of
trachelogenin 4d isolated from Ipomoea cairica [14,15],
make them the most interesting of the naturally occurring
␣-hydroxybutyrolactones 4a–g and 5a–d.
To study the mechanism by which mammalian lignans
are formed in human metabolism, various synthetic refer-
ence compounds are needed to identify the intermediates
and precursors. We present here the synthesis of (Ϯ)-7Ј-
hydroxyenterolactone, (Ϯ)-7Ј-hydroxymatairesinol and
(Ϯ)-8-hydroxyenterolactone as a mixture of diastereomers,
and the separation of these mixtures by HPLC techniques
and column chromatography, and preliminary report of the
NMR spectroscopic studies.
The synthesis of a diastereomeric mixture of (Ϯ)-para-
benzlactone and the partial synthesis of hydroxymataires-
inol have been reported [16–20]. There are no experimental
details, however, regarding the synthesis of hydroxyma-
tairesinol or the characterization of the separated isomers.
Such compounds hold considerable interest as intermediates
for the synthesis of aryltetralin lignans such as (Ϯ)-cyclo-
olivil and (Ϯ)-␣-conidendrin by intramolecular cyclisation
reactions [19,20]. Total syntheses of both racemic and op-
tically active wikstromol 4a and trachelogenin 4d have been
published [21–23].
Since the detection of the mammalian lignans enterolac-
tone 6a and enterodiol 7a in human urine [24–26], there has
been much discussion about their biological function. Es-
pecially interesting is their suggested role as antiestrogens
and anticarcinogens among other possible biological activ-
ities [27]. Enterolactone 6a, alone or together with entero-
diol 7a, has more recently been detected in human plasma
and other biological fluids as well [28–31]. Human diet has
been shown to contain plant lignans, which act as precursors
for the mammalian lignans [32–34]. The enterolignans are
produced by the action of intestinal microflora on the pre-
cursors (i.e. matairesinol 6b and secoisolariciresinol 7b) in
dietary fibre. The precursor lignans have also been detected
in human urine and plasma [28,35,36]. A third mammalian
2. Experimental
All experiments were monitored by thin layer chroma-
tography using aluminium based, precoated silica gel sheets
(Merck 60 F254, layer thickness 0.2 mm). Silica gel 60
(230–400 mesh, Merck) was used for flash column chro-
matography. Melting points were determined on an Elec-
trothermal melting point apparatus in open capillary tube
and are uncorrected. The HPLC experiments, both analyti-
cal and semi-preparative, were performed with a Waters
(Milford, MA, USA) liquid chromatograph consisting of a
Waters 600E multisolvent delivery system and a Waters 996
photodiode array detector. Components were monitored by
measuring the absorption at 260 nm. The 1H and 13C NMR
spectra were recorded on 200 MHz Varian GEMINI or 300
MHz Varian INOVA spectrometers in CDCl3 or acetone-d6
and chemical shifts are relative to internal tetramethylsilane
(TMS); J values are given in Hz. EIMS and HRMS were
obtained using JEOL JMS-SX102 spectrometer. The GC
analysis was carried out using a Hewlett Packard 6890
instrument equipped with a HP-5 crosslinked 5% phenyl

T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
779
methyl siloxane (15.0 m ϫ 0.32 mm ϫ 0.25 ␮m) capillary
column directly connected to the ion source. THF was
freshly distilled from sodium benzophenone ketyl and tol-
uene and benzene were distilled. Other solvents were of
analytical grade. The solvents used in HPLC experiments
were of HPLC grade. Other commercially available chem-
icals were used as supplied by the manufacturers.
solvents gave the crude product as an amorphic solid (0.10
g, 73%). Analysis of the H NMR spectrum of the crude
1
product revealed this material to contain a mixture of the
two diastereoisomers 1d and 2d in an approximate ratio of
1.5:1. The mixture of the two isomers was separated by
reversed-phase HPLC using a Merck LiChrospher 100 RP-
18e column (250ϫ10 mm i.d.), 5 ␮m. The mobile phase
was CH3CN/H2O (10:90 to 50:50, gradient v/v); flow rate,
2.1. (Ϯ)-trans-2-(3-Benzyloxybenzyl)-3-[3Ј-benzyloxy-␣,␣-
bis(phenylthio)benzyl]butyrolactone (12)
2.5–5.0 ml minϪ1
.
Isomer 1d: 1H NMR (acetone-d6, 300 MHz) ␦ 2.68 (1 H,
m, H-8Ј), 2.71 (1 H, dd, J 13.7, 5.0, H-7b), 2.99 (1 H, m,
H-8), 3.02 (1 H, dd, J 13.7, 4.7, H-7a), 3.88 (1 H, t, J 8.1,
H-9Јb), 4.02 (1 H, dd, J 8.1, 7.8, H-9Јa), 4.75 (1 H, d, J 5.7,
H-7Ј), 6.57 (1 H, dt, J 7.3, 1.2, H-6), 6.67 (1 H, ddd, J 7.8,
1.9, 1.0, H-4), 6.69 (1 H, t, J 1.2, H-2), 6.76 (1 H, ddd, J 8.1,
2.4, 1.0, H-4Ј), 6.82 (1 H, dt, J 7.6, 1.2, H-6Ј), 6.91 (1 H, dd,
J 2.0, 1.9, H-2Ј), 7.06 (1 H, t, J 8.6, H-5), 7.17 (1 H, t, J 7.8,
H-5Ј); 13C NMR (acetone-d6, 300 MHz) ␦ 35.7 (C-7), 43.5
(C-8), 45.8 (C-8Ј), 68.9 (C-9Ј), 74.6 (C-7Ј), 113.9 (C-2Ј),
114.3 (C-4), 115.2 (C-4Ј), 117.5 (C-2), 118.1 (C-6Ј), 121.9
(C-6), 130.0 and 130.2 (C-5 or C-5Ј), 140.5 (C-1), 145.6
(C-1Ј), 158.2 and 158.4 (C-3Ј or C-3), 179.3 (C-9); HRMS
m/z calcd for C18H18O5 (Mϩ) 314.1154, found 314.1149;
EIMS m/z 314 (Mϩ, 71%), 296 (M-H2O, 100), 268 (10),
207 (19), 189 (26), 147 (29), 123 (37), 107 (79), 95 (29), 85
(35), 77 (28).
Compound 12 was synthesized according to the reported
method [39].
2.2. (Ϯ)-trans-2-(3-Benzyloxybenzyl)-3-(3Ј-benzyloxy-␣-
benzoyl)butyrolactone (14)
A mixture of compound 12 (2.0 g, 2.88 mmol) in aqueous
THF (15%, 160 ml) and yellow mercuric oxide (2.49 g, 11.5
mmol) was placed in the reaction flask equipped with an argon
inlet and a magnetic stirrer bar. The mixture was stirred vig-
orously at room temperature while a solution of boron trifluo-
ride etherate (2.45 g, 17.3 mmol) was added dropwise. Stirring
was maintained for 4 h after which ether was added to the
reaction mixture, and the precipitated salts were filtered off.
The filtrate was washed with saturated Na2CO3 and with sat-
urated NaCl, and dried over MgSO4. Evaporation afforded a
crude product, which was dissolved in chloroform, and the
undissolved solids were filtered off. Evaporation of the chlo-
roform and purification by flash column chromatography
(CH2Cl2) gave 14 as a gum (1.07 g, 75%). Recrystallization
from a mixture of chloroform and ether gave pure 14 as a white
solid: mp 91°C: IR (KBr) vmax 1779, 1671, 1580, 1440, 1375,
1256, 1154, 1021, 786, 739, 693 cmϪ1; 1H NMR (CDCl3, 200
MHz) ␦ 2.98 (1 H, dd, J 7.5, 13.9, H-7), 3.14 (1 H, dd, J 5.4,
14.0, H-7), 3.53 (1 H, ddd, J 5.4, 7.4, 8.2, H-8), 4.05 (1 H, m,
overlapping, H-8Ј), 4.12 (1 H, t, J 8.3, H-9Ј), 4.34 (1 H, t, J 8.3,
H-9Ј), 4.89 (2 H, s, CH2), 5.05 (2 H, s, CH2), 6.68–6.80 (m,
3 ArH), 7.08–7.42 (m, 15 ArH); 13C NMR (CDCl3, 200 MHz)
␦ 34.96, 44.35, 47.07, 67.94, 69.67, 70.14, 113.56, 113.61,
115.51, 120.86, 121.13, 121.79, 127.33, 127.45, 127.86,
128.18, 128.47, 128.62, 129.82, 136.15, 136.71, 138.48,
158.91, 159.04, 176.91, 196.24; HRMS m/z calcd for
C32H28O5 (Mϩ) 492.1937, found 492.1935; EIMS m/z 492
(Mϩ, 28%), 401 (8), 281 (4), 211 (3), 181 (7), 106 (6), 91
(100), 77 (5).
Isomer 2d: 1H NMR (acetone-d6, 300 MHz) ␦ 2.64 (1 H,
qd, J 8.7, 4.8, H-8Ј), 2.76 (1 H, dd, J 13.7, 5.5, H-7b), 2.85
(1 H, dd, J 13.7, 6.5, H-7a), 2.95 (1 H, ddd, J 8.7, 6.5, 5.5,
H-8), 3.90 (1 H, t, J 8.7, H-9Јb), 4.21 (1 H, t, J 8.7, H-9Јa),
4.51 (1 H, d, J 4.8, H-7Ј), 6.67 (1 H, dm, J 7.8, H-6), 6.70
(1 H, dm, J 7.8, H-4), 6.73 (1 H, dm, J 7.8, H-4Ј), 6.76 (1
H, dm, J 7.8, H-6Ј), 6.77 (1 H, m, H-2), 6.86 (1 H, t, J 2.0,
H-2Ј), 7.11 (1 H, t, J 7.8, H-5), 7.15 (1 H, t, J 7.8, H-5Ј); 13
C
NMR (acetone-d6, 300 MHz) ␦ 35.4 (C-7), 43.4 (C-8), 47.2
(C-8Ј), 67.5 (C-9Ј), 72.8 (C-7Ј), 113.5 (C-2Ј), 114.4 (C-4),
115.1 (C-4Ј), 117.2 (C-6Ј), 117.5 (C-2), 121.4 (C-6), 130.2
(C-5 and C-5Ј), 140.6 (C-1), 145.9 (C-1Ј), 158.4 (C-3 and
C-3Ј), 179.0 (C-9); HRMS m/z calcd for C18H18O5 (Mϩ)
314.1154, found 314.1152; EIMS m/z 314 (Mϩ, 19%), 296
(M-H2O, 100), 268 (7), 207 (14), 189 (18), 149 (25), 121
(26), 107 (39), 95 (17), 85 (15), 77 (16).
2.4. (Ϯ)-trans-2-(3-Methoxy-4-benzyloxybenzyl)-3-[3Ј-
methoxy-4Ј-benzyloxy-␣,␣-bis(phenylthio)benzyl]butyro-
lactone (13)
2.3. (8R*,8ЈR*,7ЈR*)-(Ϯ)-7Ј-Hydroxyenterolactone (1d)
and (8R*,8ЈR*,7ЈS*)-(Ϯ)-7Ј-Hydroxyenterolactone (2d)
Compound 13 was prepared according to the reported
method [39]. The crude product was used directly in the
next step without purification.
Compound 14 (0.22 g, 0.45 mmol) was dissolved in
small amounts of tetrahydrofuran (5 ml), and ethanol (50
ml) and W-2 Raney nickel (7.3 g) was added to the solution.
The reaction mixture was stirred for 1 h under hydrogen
atmosphere at room temperature. The catalyst was removed
by filtration and rinsed with acetone. Evaporation of the
2.5. (Ϯ)-trans-2-(3-Methoxy-4-benzyloxybenzyl)-3-(3Ј-
methoxy-4Ј-benzyloxy-␣-benzoyl)butyrolactone (15)
Following the same procedure as for 14, compound 13
was converted to 15 as a solid in 61% yield after flash

780
T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
column chromatography (CH2Cl2). Recrystallization from a
mixture of chloroform and ether gave 15 as a white solid:
mp 163–164°C (lit. [19], 164–165°C; lit. [20], 157–
as a colorless amorphic solid (1.02 g, 89%): 1H NMR
(CDCl3, 200 MHz) ␦ 2.36–2.66 (4 H, m, H-7Ј, H-8Ј, H-8),
2.88 (1 H, dd, J 6.9, 13.8, H-7), 3.05 (1 H, dd, J 4.8, 13.9,
H-7), 3.80 (1 H, dd, J 6.8, 9.1, H-9Ј), 4.04 (1 H, dd, J 6.3,
9.1, H-9Ј), 5.00 (2 H, s, CH2), 5.02 (2 H, s, CH2), 6.57–6.60
(m, 2 ArH), 6.74–6.87 (m, 4 ArH), 7.13–7.40 (m, 12 ArH);
13C NMR (CDCl3, 200 MHz) ␦ 5.07, 38.43, 41.17, 46.22,
69.86, 71.09, 112.89, 113.37, 115.39, 115.69, 121.19,
121.85, 127.45, 127.48, 127.94, 128.03, 128.56, 128.61,
129.71, 129.74, 136.80, 136.88, 139.31, 139.53, 158.96,
159.02, 178.45; HRMS m/z calcd for C32H30O4 (Mϩ)
478.2144, found 478.2152; EIMS m/z 478 (Mϩ, 13%), 387
(10), 203 (5), 181 (8), 106 (15), 91 (100), 77 (10).
1
160.5°C). The spectral data [IR (KBr), H and 13C NMR
(CDCl3), 200 MHz] were in agreement with those of the
previously synthesized products [19,20]. HRMS m/z calcd
for C34H32O7 (Mϩ) 552.2148, found 552.2144; EIMS m/z
552 (Mϩ, 43%), 462 (7), 461 (7), 284 (5), 241 (17), 151 (8),
106 (32), 105 (29), 91 (100), 77 (25).
2.6. (8R*,8ЈR*,7ЈR*)-(Ϯ)-7Ј-Hydroxymatairesinol (1a) and
(8R*,8ЈR*,7ЈS*)-(Ϯ)-7Ј-allohydroxymatairesinol (2a)
Following the same procedure as for 1d and 2d, com-
pound 15 was converted to a mixture of compounds 1a and
2a as an oil in 64% yield. Analysis of the 1H NMR spectrum
of the crude product revealed this material to contain a
mixture of the two diastereoisomers in an approximate ratio
of 1.5:1. The mixture of the two isomers was separated by
normal-phase HPLC using a Merck LiChrospher Si-60 col-
umn (250ϫ10 mm i.d.), 5 ␮m. The mobile phase was
n-hexane/CHCl3/MeOH (70:15:15, v/v/v); flow rate, 3.0 ml
2.8. Oxidation of the metal enolate of 2,3-bis(3-
benzyloxybenzyl)butyrolactone (16)
Lithium bis(trimethylsilyl)amide (5.7 mmol) was pre-
pared in 5 ml of dry benzene by the reported method [41].
LiHMDS was placed in the reaction flask equipped with
argon inlet and magnetic stirrer bar, and 30 ml of dry
benzene was added to the solution. The solution was cooled
to 0°C and 16 (1.59 g, 3.3 mmol) in dry benzene (35 ml)
was added dropwise. The reaction mixture was stirred at
room temperature for 2 h, followed by addition of 18-
crown-6 (0.098 g, 0.37 mmol). The argon inlet was removed
and dry oxygen was bubbled through the reaction mixture
for 3 h. The mixture was quenched by addition of saturated
aqueous Na2SO3 (20 ml) and stirred for 15 min. The mix-
ture was acidified with 2 N HCl. The organic layer was
separated, and the aqueous layer was extracted with
CH2Cl2. The combined organic layers were washed with
aqueous 5% NaHCO3-solution and brine and dried over
MgSO4. Evaporation of the solvents provided the crude
product (1.59 g, 97%) as a white amorphic solid. The crude
product was purified by flash column chromatography
CH2Cl2/EtO2 (97:3) to give three fractions including 0.32 g
(19.5%) of starting material 16. The two isomers 17a and
17b were recovered in 0.37 g (22.6%) and 0.27 g (16.5%),
respectively.
minϪ1
.
The spectral data [1H NMR and 13C NMR (CDCl3 and
acetone-d6), 300 MHz] were in agreement with those of the
natural hydroxymatairesinol and allohydroxymatairesinol
[8,10].
Isomer 1a: HRMS m/z calcd for C20H22O7 (Mϩ)
374.1365, found 3374.1369; EIMS m/z 374 (Mϩ, 10%), 356
(M-H2O, 100), 241 (12), 153 (20), 137 (23).
Isomer 2a: HRMS m/z calcd for C20H22O7 (Mϩ)
374.1365, found 374.1350; EIMS m/z 374 (Mϩ, 7), 356
(M-H2O, 100), 241 (13), 153 (17), 137 (25).
2.7. (Ϯ)-trans-2,3-Bis(3-benzyloxybenzyl)butyrolactone
(16)
To a stirred solution of 12 (1.66 g, 2.4 mmol) in dry
toluene (25 ml) maintained under argon at 90°C was added
in small portions for 30 min, a mixture of tri-n-butyltin
hydride [40] (2.78 g, 9.6 mmol) and AIBN (0.098 g, 0.60
mmol). The reaction mixture was stirred for 2 h. Evapora-
tion of toluene and purification by flash column chromatog-
raphy toluene/hexane (1:1) and EtOAc/hexane (1:4) gave 16
Isomer 17a: 1H NMR (CDCl3, 200 MHz) ␦ 2.56–2.66 (2
H, m, H-7Ј), 2.90–3.23 (4 H, m, H-8Ј, H-7, OH), 3.94–4.11
(2 H, m, H-9Ј), 5.08 (4 H, s, CH2), 6.75–6.97 (m, 6 ArH),
7.22–7.50 (m, 12 ArH); 13C NMR (CDCl3, 200 MHz) ␦
Scheme 1.

T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
781
1.88, 42.25, 43.52, 69.82, 69.86, 70.17, 76.25, 112.84,
113.88, 115.57, 116.67, 121.43, 122.80, 127.43, 127.50,
127.91, 127.95, 128.50, 128.55, 129.64, 129.69, 135.89,
136.77, 136.83, 140.13, 158.89, 159.00, 178.47; HRMS m/z
calcd for C32H30O5 (Mϩ) 494.2093, found 494.2090; EIMS
m/z 494 (Mϩ, 13%), 403 (8), 287 (4), 197 (7), 181 (7), 106
(11), 91 (100), 77 (9).
(C-6Ј), 122.4 (C-6), 129.9 (C-5), 130.5 (C-5Ј), 137.7 (C-1),
141.5 (C-1Ј), 158.0 (C-3), 158.5 (C-3Ј), 177.9 (C-9); HRMS
m/z calcd for C18H18O5 (Mϩ) 314.1154, found 314.1155;
EIMS m/z 314 (Mϩ, 47%), 279 (20), 189 (19), 167 (28), 149
(66), 133 (25), 108 (100), 107 (91).
1
Isomer 17b: H NMR (CDCl3, 200 MHz) ␦ 2.67 (1 H,
3. Results and discussion
dd, J 11.6, 12.8, H-7Ј), 2.84–3.00 (4 H, m, H-8Ј, H-7, OH),
3.16 (1 H, dd, J 3.7, 13.2, H-7Ј), 3.85 (1 H, m, H-9Ј), 4.14
(1 H, dd, J 7.6, 9.1, H-9Ј), 5.07 (4 H, s, CH2), 6.77–6.97 (m,
6 ArH), 7.22–7.48 (m, 12 ArH); 13C NMR (CDCl3, 200
MHz) ␦ 2.35, 38.56, 47.87, 69.25, 69.94, 75.86, 113.03,
114.05, 115.26, 116.94, 121.01, 122.94, 127.46, 127.54,
127.96, 128.04, 128.57, 128.61, 129.62, 129.92, 134.85,
136.79, 136.84, 139.44, 158.87, 159.09, 177.53; HRMS m/z
calcd for C32H30O5 (Mϩ) 494.2094, found 494.2098; EIMS
m/z 494 (Mϩ, 17%), 403 (5), 287 (8), 197 (7), 181 (6), 106
(8), 91 (100), 77 (6).
The trans-␣,␤-dibenzyl-␥-butyrolactone framework is
generally obtained by the Michael addition of an anion
derived from dithioacetal to butenolide followed by benzy-
lation in situ (Scheme 1) [39,42,43].
The introduction of a secondary hydroxyl group in the
benzylic position is presented in Scheme 2. The bis(phenyl-
thio) moiety can be hydrolyzed to parent carbonyl group
either by treatment with iodine in refluxing methanol [44] or
hydrolysis with mercuric oxide and boron trifluoride ether-
ate in aqueous tetrahydrofuran [45]. The former procedure
with the trans-adduct 12 or 13 gave a mixture of reaction
products in low yields, whereas hydrolysis with mercuric
oxide produced a clean reaction to give the carbonyl com-
pound 14 or 15. In the next step the aim was to reduce the
carbonyl group and remove the benzyl ether protective
groups simultaneously. Catalytic hydrogenation under stan-
dard conditions using Raney nickel proceeded smoothly to
afford a diastereomeric pair of alcohols 1a and 2a or 1d and
2.9. (8S*,8ЈS*)-(Ϯ)-8-Hydroxyenterolactone (4h) and
(8R*,8ЈS*)-(Ϯ)-8-hydroxyenterolactone (5h)
A suspension of 17a (0.27g, 0.55 mmol) in ethanol (125
ml) and W-2 Raney nickel (12 g) was refluxed for 4 h. The
catalyst was removed by filtration and rinsed with acetone.
Evaporation of the solvents left the crude product, which
was purified by flash column chromatography CH2Cl2/ace-
1
2d in a ratio of ca. 1.5:1. The ratio was determined by H
1
tone (4:1) to give 4h (0.16 g, 67%): H NMR (acetone-d6,
NMR and GLC. The isomeric products were separated by
semi-preparative HPLC. Satisfactory separation of the iso-
mers of hydroxymatairesinol 1a and 2a was achieved using
normal-phase silica HPLC column, whereas no separation
between the isomers of hydroxyenterolactone 1d and 2d
was accomplished. The HPLC column was therefore
changed to C18 reversed-phase column. The diastereomers
were characterized by NMR analysis and molecular mod-
elling [46], and the results were compared with those of
Kawamura et al. [8] and Mattinen et al. [10]. Although
definite conclusions on the absolute configurations made by
NMR analyses are not possible [10] by NMR, as proposed
by Kawamura et al. [8], it should be possible to assign the
relative configuration at C-7Ј using molecular modelling to
obtain minimum energy conformations and NMR analyses
to obtain average coupling constants between H-8Ј and
H-7Ј. Also the NOE interactions should be different for the
two diastereomers. We will report shortly on these results
[46].
The introduction of a tertiary hydroxyl ␣ to the lactone
carbonyl group is presented in Scheme 3. ␣-Hydroxylation
of carbonyl compounds, such as lignan lactones involves
generally oxidation of a metal enolate [21,22]. For optimal
results, the enolate was generated by hexamethyldisilazane
from the benzyl lactone 16, obtained from the bis(thioether)
12 by reduction with tributyltin hydride in the presence of
AIBN [47]. A variety of oxidants have been developed for
␣-hydroxylation, and molecular oxygen has been found to
300 MHz) ␦ 2.51 (1 H, m, H-8Ј), 2.58 (1 H, dd, J 13.1, 10.5,
H-7Јb), 2.83 (1 H, dd, J 13.1, 3.9, H-7Јa), 3.00 (1 H, d, J
13.4, H-7b), 3.17 (1 H, d, J 13.4, H-7a), 3.94 (1 H, dd, J 8.7,
7.3, H-9Јb), 4.00 (1 H, t, J 8.7, H-9Јa), 5.17 (1 H, s, 8-OH),
6.64–6.72 (4 H, m, H-6Ј, H-2Ј, H-4Ј, H-4), 6.74 (1 H, m,
H-6), 6.82 (1 H, t, J 2.1, H-2), 7.10 (1 H, t, J 7.4, H-5Ј), 7.14
(1 H, t, J 8.2, H-5), 8.24 and 8.29 (1 H, s, 3-OH or 3Ј-OH);
13C NMR (acetone-d6, 300 MHz) ␦ 32.0 (C-7Ј), 41.7 (C-7),
43.8 (C-8Ј), 70.5 (C-9Ј), 76.4 (C-8), 113.9 (C-4Ј), 114.4
(C-4), 116.3 (C-2Ј), 117.7 (C-2), 120.5 (C-6Ј), 122.2 (C-6),
129.9 (C-5), 130.1 (C-5Ј), 137.8 (C-1), 141.4 (C-1Ј), 158.0
and 158.1 (C-3Ј or C-3), 178.1 (C-9); HRMS m/z calcd for
C18H18O5 (Mϩ) 314.1154, found 314.1151; EIMS m/z 314
(Mϩ, 60%), 189 (28), 161 (8), 145 (16), 134 (17), 108 (93),
107 (100), 91 (4), 77 (12).
1
Similar treatment of 17b gave 5h (0.08 g, 12%): H
NMR (acetone-d6, 300 MHz) ␦ 2.69 (1 H, m, H-7Јb), 2.81
(1 H, m, H-8Ј), 2.99 (1 H, d, J 14.3, H-7b), 3.06 (1 H, m,
H-7Јa), 3.12 (1 H, d, J 14.3, H-7a), 3.83 (1 H, t, J 8.8, 8.7,
H-9Јb), 4.11 (1 H, dd, J 8.8, 7.1, H-9Јa), 4.73 (1 H, s,
8-OH), 6.68 (1 H, dt, J 8.0, 1.2, H-6Ј), 6.69 (1 H, br s, H-2Ј),
6.71 (1 H, m, H-4Ј), 6.74 (1 H, ddd, J 8.0, 2.4, 1.0, H-4),
6.85 (1 H, dt, J 8.0, 1.3, H-6), 6.88 (1 H, dd, J 2.4, 1.3, H-2),
7.13 (2 H, t, J 8.0, H-5 and H-5Ј), 8.23 (1 H, s, 3-OH), 8.28
(1 H, s, 3Ј-OH); 13C NMR (acetone-d6, 300 MHz) ␦ 32.8
(C-7Ј), 39.3 (C-7), 49.5 (C-8Ј), 69.3 (C-9Ј), 77.4 (C-8),
114.2 (C-4), 114.6 (C-4Ј), 116.3 (C-2Ј), 118.2 (C-2), 120.5

782
T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
Scheme 3. Reagents and conditions: (a) n-Bu3SnH, AIBN/toluene; (b)
LiHMDS, 18-crown-6, [O]/benzene; (c) separation; (d) MeI, KOH,
DMSO; (e) Raney nickel, ethanol, reflux.
hols to ␣ methyl ethers 18a and 18b by methylation with
MeI and KOH in DMSO [46,49]. A strong NOESY corre-
lation was found in NMR analyses between the methoxy
group at C-8 and proton at C-8Ј in isomer 18b but not in
isomer 18a. The benzyl ether protecting groups were re-
moved from the separated isomers 17a and 17b with Raney
nickel in refluxing ethanol instead of hydrogenation under
standard conditions in order to avoid a mixture of products.
A minor problem, not encountered with isomer 17a, was the
partial deoxygenation of the tertiary alcohol in isomer 17b
by Raney nickel [50]. The isomeric products 4h and 5h
were fully characterized with NMR spectroscopy [46].
Scheme 2. Reagents and conditions: (a) compound 8 or 9, n-butyllithium,
THF, Ϫ78°C, then 2-butenolide, THF, Ϫ78°C, then benzyl bromide 10 or
11, HMPA, THF, Ϫ78°C; (b) HgO, BF3 ⅐ OEt2/THF-H2O; (c) H2, Raney
nickel, ethanol; (d) separation.
produce the two diastereomers in about equal amounts [21–
23,48]. Although certain other oxidants would presumably
have given a more selective reaction, both diastereomers
were in fact desirable at this stage to allow the confirmation
of the stereostructures of the natural products. The enolate
oxidation produced a mixture of diastereomeric alcohols
17a and 17b in a ratio of ca. 1.4:1, and the alcohols were
isolated by column chromatography to give the two tertiary
alcohols 17a and 17b in 39.1% yield (if recovered starting
material is taken into account, the overall yield is 58.6%).
Careful examination of the spectral data revealed that the
major product was the isomer 17a, which was also con-
firmed by conversion of the protected stereoisomeric alco-
Acknowledgments
We thank Dr. Jorma Matikainen for running the mass
spectra.
References and notes
[1] Freudenberg K, Knof L. The lignans of fir wood. Chem Ber 1957;
90:2857–69.

T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
783
[2] Nishibe S, Chiba M, Sakushima A, Hisada S, Yamanouchi S, Takido
M, Sankawa U, Sakakibara A. Introduction of an alcoholic hydroxyl
group into 2,3-dibenzylbutyrolactone lignans with oxidizing agents
and carbon-13 nuclear magnetic resonance spectra of the oxidation
products. Chem Pharm Bull 1980;28:850–60.
[3] Wada K, Munakata K. (Ϫ)-Parabenzlactone, a new piperolignanolide
isolated from Parabenzoin trilobum Nakai. Tetrahedron Lett
1970:2017–9.
[24] Stitch SR, Toumba JK, Groen MB, Funke CW, Leemhuis J, Vink J,
Woods GF. Excretion, isolation and structure of a new phenolic
constituent of female urine. Nature 1980;287:738–740.
[25] Setchell KDR, Lawson AM, Mitchell FL, Adlercreutz H, Kirk DN,
Axelson M. Lignans in man and animal species. Nature 1980;287:
740–2.
[26] Setchell KDR, Lawson AM, Conway E, Taylor NF, Kirk DN, Cooley
G, Farrant RD, Wynn S, Axelson M. The definitive identification of
the lignans trans-2,3-bis(3-hydroxybenzyl)-␥-butyrolactone and 2,3-
bis(3-hydroxybenzyl)butane-1,4-diol in human and animal urine.
Biochem J 1981;197:447–58.
[4] Niwa M, Iguchi M, Yamamura S, Nishibe S. The stereostructure of
acetylparabenzlactone and its conversion to a lariciresinol-type lac-
tone. Bull Chem Soc Jpn 1976;49:3359–60.
[5] Marco JA, Sanz JF, Sancenon F, Susanna A, Rustaiyan A, Saberi M.
Sesquiterpene lactones and lignans from Centaurea species. Phyto-
chemistry 1992;31:3527–30.
[6] Siqueira JBG, Zoghbi M das GB, Cabral JA, Filho WW. Lignans
from Protium tenuifolium. J Nat Prod 1995;58:730–2.
[27] Adlercreutz H, Mazur W. Phyto-oestrogens and Western diseases.
Ann Med 1997;29:95–120.
[28] Adlercreutz H, Fotsis T, Lampe J, Wa¨ha¨la¨ K, Ma¨kela¨ T, Brunow G,
Hase T. Quantitative determination of lignans and isoflavonoids in
plasma of omnivorous and vegetarian women by isotope dilution gas
chromatography-mass spectrometry. Scand J Clin Lab Invest 1993;53
(suppl 215):5–18.
[7] Goldschmid O, Hergert HL. Examination of Western hemlock for
lignin precursors. Tappi 1961;44:858–70.
[8] Kawamura F, Ohashi H, Kawai S, Teratani F, Kai Y. Photodiscol-
oration of Western hemlock (Tsuga heterophylla) sapwood II. Struc-
tures of constituents causing photodiscoloration. Mokuzai Gakkaishi
1996;42:301–7.
[9] Kawamura F, Miyachi M, Kawai S, Ohashi H. Photodiscoloration of
Western hemlock (Tsuga heterophylla) sapwood III. Early stage of
photodiscoloration reaction with lignans. J Wood Sci 1998;44:47–55.
[10] Mattinen J, Sjo¨holm R, Ekman R. NMR-spectroscopic study of hy-
droxymatairesinol, the major lignan in Norway spruce (Picea abies)
heartwood. ACH-Models Chem 1998;135:583–90.
[29] Dehennin L, Reiffsteck A, Jondet M, Thibier M. Identification and
quantitative estimation of a lignan in human and bovine semen. J
Reprod Fert 1982;66:305–9.
[30] Adlercreutz H, Fotsis T, Bannwart C, Ma¨kela¨ T, Wa¨ha¨la¨ K,
Brunow G, Hase T. Assay of lignans and phytoestrogens in urine
of women and in cow milk by GC/MS (SIM): In: Todd JFJ, editor.
Advances in Mass Spectrometry 1985: proceedings of the 10th
International Mass Spectrometry Conference. Chichester: John
Wiley, 1986;1293–4.
[31] Finlay EMH, Wilson DW, Adlercreutz H, Griffiths K. The identifi-
cation and measurement of ‘phyto-oestrogens’ in human saliva,
plasma, breast aspirate or cyst fluid, and prostatic fluid using gas
chromatography-mass spectrometry. J Endocrinol 1991;129 (suppl.),
Abstract No. 49.
[11] Shain L, Hillis WE. Phenolic extractives in Norway spruce and their
effects on Fomes annosus. Phytopathology 1971;61:841–5.
[12] Ward RS. Lignans, neolignans and related compounds. Nat Prod Rep
1997;14:43–74 and references cited therein.
[13] Tandon S, Rastogi RP. Wikstromol, a new lignan from Wikstroemia
viridiflora. Phytochemistry 1976;15:1789–91.
[14] Schro¨der HC, Merz H, Steffen R, Mu¨ller WEG, Sarin PS, Trumm S,
Schulz J, Eich E. Differential in vitro anti-HIV activity of natural
lignans. Z Naturforsch 1990;45c:1215–21.
[15] Trumm S, Eich E. Cytostatic activities of lignanolides from Ipomoea
cairica. Planta Med 1989;55:658–9.
[16] Miyata O, Nishiguchi A, Ninomiya I, Naito T. Hydroximate as a
synthetically useful functional group. Part II: Synthesis of (Ϯ)-oxo-
parabenzlactone. Chem Pharm Bull 1996;44:1285–7.
[32] Axelson M, Setchell KDR. The excretion of lignans in rats-evidence
for an intestinal bacterial source for this new group of compounds.
FEBS Lett 1981;123:337–42.
[33] Axelson M, Sjo¨vall J, Gustafsson BE, Setchell KDR. Origin of
lignans in mammals and identification of a precursor from plants.
Nature 1982;298:659–60.
[34] Borriello SP, Setchell KDR, Axelson M, Lawson AM. Production
and metabolism of lignans by the human faecal flora. J Appl Bacteriol
1985;58:37–43.
[35] Bannwart C, Adlercreutz H, Fotsis T, Wa¨ha¨la¨ K, Hase T, Brunow
G. Identification of O-desmethylangolensin, a metabolite of daid-
zein, and of matairesinol, one likely plant precursor of the animal
lignan enterolactone, in human urine. Finn Chem Lett
1984;120–5.
[17] Boissin P, Dhal R, Brown E. Lignans. Part 14. Study of bromination
in the benzylic position of lignan precursors. A general route leading
to retrolignans of the (Ϫ)-␣-conidendrin series. J Chem Res (S)
1991;332–3.
[18] Asano Y, Kamikawa T, Tokoroyama T. A simple method for the
synthesis of lignan skeleton. Syntheses of (Ϯ)-parabenzlactone and
(Ϯ)-hinokinin. Bull Chem Soc Jpn 1976;49:3232–5.
[19] Moritani Y, Ukita T, Hiramatsu H, Okamura K, Ohmizu H, Iwasaki
T. A highly stereoselective synthesis of 3-hydroxy-1-aryltetralin lig-
nans based on the stereoselective hydroxylation of ␣,␤-dibenzyl-␥-
butyrolactones: the first synthesis of (Ϯ)-cycloolivil. J Chem Soc,
Perkin Trans 1 1996;2747–53.
[36] Bannwart C, Adlercreutz H, Wa¨ha¨la¨ K, Brunow G, Hase T. Detection
and identification of the plant lignans lariciresinol, isolariciresinol and
secoisolariciresinol in human urine. Clin Chim Acta 1989;180:293–
301.
[37] Bannwart C, Adlercreutz H, Ma¨kela¨ T, Brunow G, Hase T. Identifi-
cation of a new mammalian lignan, 7-hydroxyenterolactone in human
urine by GC/MS. 11th International Congress on Mass Spectrometry,
Bordeaux, France, 1988.
[20] Dhal R, Nabi Y, Brown E. Study of lignans. Part 7. Total synthesis of
(Ϯ)-␣- and ␤-conidendrins and methyl (Ϯ)-␣- and ␤-conidendrals.
Tetrahedron 1986;42:2005–16.
[21] Belletire JL, Fry DF. Total synthesis of (Ϯ)-wikstromol. J Org Chem
1988;53:4724–9.
[22] Khamlach K, Dhal R, Brown E. Total synthesis of (Ϫ)-trachelogenin,
(Ϫ)-nortrachelogenin and (ϩ)-wikstromol. Tetrahedron Lett 1989;
30:2221–4.
[38] Adlercreutz H, Mousavi Y, Loukovaara M, Ha¨ma¨la¨inen E. Lignans,
isoflavones, sex hormone metabolism and breast cancer: In: Hochberg
RB, Naftolin F, editors. The New Biology of Steroid Hormones. New
York: Raven Press, 1991:145–154.
[39] Adlercreutz H, Musey PI, Fotsis T, Bannwart C, Wa¨ha¨la¨ K, Ma¨kela¨
T, Brunow G, Hase T. Identification of lignans and phytoestrogens in
urine of chimpanzees. Clin Chim Acta 1986;158:147–54.
¨
[40] Szammer J, Otvo¨s L. A convenient preparation of tri-n-butyltin hy-
[23] Moritani Y, Ukita T, Nishitani T, Seki M, Iwasaki T. A synthesis of
dride. Chem Ind 1988;764.
␣-substituted
trans-␣,␤-dibenzyl-␥-butyrolactones:diastereofacial
[41] Rathke MW. ␤-Hydroxy esters from ethyl acetate and aldehydes or
ketones: ethyl 1-hydroxycyclohexylacetate. Org Synth 1988;6:598–
600.
differentiation in the electrophilic attack on the metal enolates of
␣,␤-dibenzyl-␥-butyrolactones. Tetrahedron Lett 1990;31:3615–8.

784
T.H. Ma¨kela¨ et al. / Steroids 66 (2001) 777–784
[42] Ziegler FE, Schwartz JA. Synthetic studies on lignan lactones: aryldi-
thiane route to (Ϯ)-podorhizol and (Ϯ)-isopodophyllotoxone and
approaches to the stegane skeleton. J Org Chem 1978;43:985–91.
[43] Pelter A, Ward RS, Satyanarayana P, Collins P. Synthesis of lignan
lactones by conjugate addition of thioacetal carbanions to butenolide.
J Chem Soc, Perkin Trans 1 1983;643–7.
[44] Trost BM, Salzmann TN, Hiroi K. New synthetic reactions. Sulfeny-
lations and dehydrosulfenylations of esters and ketones. J Am Chem
Soc 1976;98:4887–902.
[47] Buynak JD, Rao MN, Pajouhesh H, Chandrasekaran RY, Finn K.
Useful chemistry of 3-(1-methylethylidene)-4-acetoxy-2-azetidinone:
a formal synthesis of (Ϯ)-asparenomycin C. J Org Chem 1985;50:
4245–52.
[48] Belletire JL, Ho DM, Fry DF. Stereoselectivity questions in the
synthesis of wikstromol. J Nat Prod 1990;53:1587–92.
[49] Johnstone RAW, Rose ME. A rapid, simple and mild procedure for
alkylation of phenols, alcohols, amides and acids. Tetrahedron 1979;
35:2169–73.
[45] Vedejs E, Fuchs PL. An improved aldehyde synthesis from 1,3-
dithianes. J Org Chem 1971;36:366–7.
[46] Ma¨kela¨ T, Kaltia S, Koskimies J, Wa¨ha¨la¨ K, Hase T, unpublished results.
[50] Krafft ME, Crooks III WJ, Zorc B, Milczanowski SE. Reaction
of Raney nickel with alcohols. J Org Chem 1988;53:3158–
63.