Synthesis of variously oxidized abietane diterpenes and their antibacterial activities against MRSA and VRE

Article abstract of DOI:10.1016/S0968-0896(00)00253-4

Variously oxidized 12 natural abietanes, 6,7-dehydroferruginol methyl ether (3), ferruginol (5), 11-hydroxy-12-oxo-7,9(11),13-abietatriene (7), royleanone (9), demethyl cryptojaponol (12), salvinolone (14), sugiol methyl ether (16), sugiol (17), 5,6-dehyd

Full text of DOI:10.1016/S0968-0896(00)00253-4

Bioorganic & Medicinal Chemistry 9 (2001) 347±356
Synthesis of Variously Oxidized Abietane Diterpenes and Their
Antibacterial Activities Against MRSA and VRE
Zhixiang Yang,a Yoshikazu Kitano,a Kazuhiro Chiba,a Naohiro Shibata,b
Hiroshi Kurokawa,b Yohei Doi,b Yoshichika Arakawab and Masahiro Tadaa,*
aLaboratory of Bioorganic Chemistry, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183±8509, Japan
bDepartment of Bacterial and Blood Products, National Institute of Infectious Disease, Gakuen, Musashi-Murayama,
Tokyo 208±0011, Japan
Received 18 July 2000; accepted 14 September 2000
AbstractÐVariously oxidized 12 natural abietanes, 6,7-dehydroferruginol methyl ether (3), ferruginol (5), 11-hydroxy-12-oxo-
7,9(11),13-abietatriene (7), royleanone (9), demethyl cryptojaponol (12), salvinolone (14), sugiol methyl ether (16), sugiol (17), 5,6-
dehydrosugiol methyl ether (19), 5,6-dehydrosugiol (20), 6b-hydroxyferruginol (23), and taxodione (25) were synthesized. Anti-
microbial activities of synthesized phenolic diterpenes and their related compounds against MRSA and VRE were evaluated.
Phenols (12-hydroxyabieta-8,11,13-trien-6-one 22 and 23), catechols (12 and 14) and taxodione 25 showed potent activity with 4±
10 mg/mL of MIC against MRSA and 4±16 mg/mL of MIC against VRE. (À)-Ferruginol showed more potent activity than natural
type (+)-ferruginol. Quinone methide 7 showed the most potent activity with 0.5±1 mg/mL of MIC against both MRSA and VRE.
# 2001 Elsevier Science Ltd. All rights reserved.
Introduction
ether (3),15 ferruginol (5),14,16,17 11-hydroxy-12-oxo-
7,9(11),13-abietatriene (7),6 royleanone (9),16 demethyl-
cryptojaponol (12),18 salvinolone (14),19,20 sugiol methyl
ether (16),21,22 sugiol (17),13,15,21 5,6-dehydrosugiol
methyl ether (19),21,22 5,6-dehydrosugiol (20),12,21,23 6b-
hydroxyferruginol (23),24 and taxodione (25)12,16,25
using a previously reported synthetic route,14 together
with antimicrobial activity of the synthesized natural
diterpenes and the related compounds against MRSA
and VRE.
Infections caused by bacteria resistant to multiple anti-
biotics have been signi®cant problems recently. In par-
ticular, methicillin-resistant Staphylococcus aureus
(MRSA) and vancomycin-resistant Enterococcus (VRE)
are increasingly found worldwide in hospitals. From the
search about novel antibiotic compounds, totarol was
found to have potent antibacterial activity against
MRSA.1 Evans reported antibacterial activity of
totarol, ferruginol and their abietane derivatives against
MRSA.2 Abietane diterpenes are widely distributed
natural products in the plant kingdom with various
biological activities, e.g. anti-virus,3,4 antibiotic,4À9 anti-
malarial,10 anti-oxidant11 and anti-tumor12,13 activities.
We planned to synthesize variously oxidized abietanes
(11-phenol, 11,12-cathecol, p-quinone methide, and
ketone/alcohol at C-6 and C-7) to examine the struc-
ture±activity-relationship against VRE and MRSA.
Previously we reported stereoselective synthesis of (+)-
and (À)-ferruginol via asymmetric polyene cyclization.14
In this paper, we report the synthesis of 12 natural
abietane-type diterpenes, 6,7-dehydroferruginol methyl
Results and Discussion
Synthetic plan
We reported enantioselective total synthesis of (+)- and
(À)-ferruginol via asymmetric polyene cyclization in our
previous paper.14 We thus planned to synthesize 12
natural abietanes from tricyclic compound 3, as com-
mon synthetic intermediate, which could be prepared
from acid 1 by two steps. Three synthetic routes (A, B
and C) were devised from 3. The synthetic routes are
summarized as follows. The ®rst route (A) was branched
from 3 to ferruginol 5 which was converted to 7, 9, 12
and 14. The second route (B) was branched from 3 to
7-ketone 16 via hydroboration of 3 followed by oxidation
*Corresponding author. Fax: +81-042-367-5699; e-mail:
tada@cc.tuat.ac.jp
0968-0896/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(00)00253-4

348
Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
of the products. The ketone 16 was further transformed
to 17, 19 and 20. The third route (C) was branched from
3 to 6-alcohol 23. The alcohol 23 was oxidized to cate-
chol ester (11-hydroxy-12-benzoyl ester) and ®nally
converted to taxodione (25) (Scheme 1).
introduced to variously oxidized abietanes. The spectral
data of synthetic 3 showed that it is identical with the
natural 3 in the literature (Scheme 2).15
The ®rst route (A)
Ferruginol (5),14,16,17 11-hydroxy-12-oxo-7,9(11),13-
abietatriene (7),6 royleanone (9),16 demethylcryptojapo-
nol (12)18 and salvinolone (14)19,20 were synthesized
from 3 as follows. The double bond at C6±C7 of 3 was
hydrogenated with H2 and 10% Pd/C in ethyl acetate to
yield 4 (quantitative yield). The methyl ether 4 was
treated with boron tribromide in dichloromethane at 0±
5 ꢀC for 2 h to give ferruginol (5)14,16,17 (94.9%), which
was identi®ed by comparing the spectral data with those
of natural 5 in the literature. Another experiment for
the demethylation of 4 was performed with NaH±EtSH
in DMF at 120 ꢀC to give only 40% of 5. The oxidation
Tricyclic intermediate 3
Tricyclic intermediate, 6,7-dehydroferruginol methyl
ether 3, was synthesized by two steps from acid 1 which
was prepared via polyene cyclization reaction in our
previous report.14 Isopropyl group at C-13 was intro-
duced directly by Friedel±Crafts alkylation of 1 with 2-
chloropropane and AlCl3 in dichloromethane to a€ord
2 (80.9%), which was further decarboxylated with
Pb(OAc)4±Cu(OAc)2 in quinoline to give 6,7-dehy-
droferruginol methyl ether (3) (87.4%). Methyl ether 3,
as a common intermediate of our synthesis, was
Scheme 1. Synthetic plan of highly oxidized 12 natural abietanes.

Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
349
of C-11 position of ferruginol (5) with benzoyl peroxide
(BPO) in chloroform a€orded 12-benzoyloxy-11-hydro-
xyabieta-8,11,13-triene (6)26 (71.4%). The reductive
deprotection of benzoyl group at C-12 of 6 with diiso-
butylaluminum hydride (DIBAL) in THF at À15 ꢀC
for 3 h followed by auto-oxidation with air gave 11-
hydroxy-12-oxo-7,9(11),13-abietatriene (7)6 in poor yield
(15.1%). We also tried the similar reaction of 6 with
lithium aluminum hydride, but resulted in poorer yield
of 7 (5.4%). The spectral data of synthetic material 7
were identical with those of natural 7 in the literature.
groups were hydrolyzed by heating under re¯ux with
NaHCO3 in MeOH±H2O to a€ord salvinolone (14)19,20
(87.8%), whose spectral properties were identical to
those in the literature (Scheme 2).
The second route (B)
Sugiol methyl ether (16),21,22 sugiol (17),13,15,21 5,6-
dehydrosugiol methyl ether (19),21,22 and 5,6-dehydro-
sugiol (20)12,21,23 were synthesized from 3 as follows.
Hydroboration of 3 with BH3 in tetrahydrofuran (THF)
followed by oxidation with H2O2 in NaOH±H2O gave
alcohols (15a) of a yellow oil and (15b) as colorless
needles (1:1) (72.0% total yield of 15a and 15b from 3).
The stereochemistry at C-7 of 15a (7b-H) and 15b (7a-
H) was certi®ed by the splitting pattern of 7-H (15a: d,
J=4.4 Hz; 15b: dd, J=3.6, 1.6 Hz). Oxidation of the
mixture of alcohols 15a and 15b with Jones' reagent in
acetone at 0 ꢀC for 20 min gave sugiol methyl ether
(16)21,22 in 85.2% yield. Demethylation of 16 with
NaH±EtSH in DMF at 120 ꢀC under re¯ux for 3 h
a€orded sugiol (17)13,15,21 as colorless needles in satis-
factory yield (98.7%). The spectra of the synthetic 16
and 17 were identical in every respect to those of natural
compounds, respectively.
Treatment of
6 with meta-chloroperbenzoic acid
(mCPBA) in dichloromethane at room temperature
yielded quinone 8 (42.3%),27 which was further hydro-
lyzed with NaHCO3 in MeOH±H2O under re¯ux to
give royleanone (9)16 in 85.0% yield as yellow needles
whose spectral properties were identical to those of the
literature.
The acetylation of 6 with isopropenyl acetate in re¯ux-
ing toluene gave an acetate 10 (76.7%), which was oxi-
dized with chromium trioxide in acetic acid to give
ketone 11 (65.9%). Ketone 11 was further hydrolyzed
with NaHCO3 in MeOH±H2O to give demethylcrypto-
japonol (12)18 in quantitative yield whose spectral
properties were identical to those of natural 12.
Treatment of 16 with sulfuryl chloride in CCl4 at ambi-
ent temperature for 20 h gave 18 (97.7%). Chloride 18
was dehydrochlorinated with lithium chloride in pyri-
dine at 110 ꢀC to give 5,6-dehydrosugiol methyl ether
(19)21,22 as needles (85.9%) whose spectral properties
were identical to those of natural 19. Methyl ether 19
Treatment of 11 with sulfuryl chloride (SO2Cl2) in CCl4
at 60 ꢀC for 40 h gave 13 (94.9%). Chloroketone 13 was
dehydrohalogenated with lithium chloride in re¯uxing
pyridine to give the a,b-unsaturated ketone whose ester
Scheme 2. Reagents and conditions: (a) Me2CHCl, AlCl3, CH2Cl2, 40 ꢀC, 40 h, 80.9%; (b) LTA, Cu(OAc)2, quinoline, 125 ꢀC, 16 h, 87.4%; (c) H2,
Pd/C, EtOAc, rt, 98.3%; (d) BBr3, CH2Cl2, 0±5 ꢀC, 2 h, 94.9%; (e) BPO, CHCl3, rt, 7 h, 71.4%; (f) i. DIBAL-H, THF, À15 ꢀC, 3 h; ii. O2, two steps,
15.1%; (g) mCPBA, CH2Cl2, rt, 12 h, 42.3%; (h) NaHCO3, MeOH±H2O, re¯ux, 85%; (i) isopropenyl acetate, TsOH, PhMe, re¯ux, 5 h, 76.7%;
(j) CrO3, AcOH, rt, 8 h, 65.9%; (k) NaHCO3, MeOH±H2O, re¯ux, 96.3%; (l) SO2Cl2, CCl4, 60 ꢀC, 40 h, 94.9%; (m) i. LiCl, pyridine, re¯ux, 10 h;
ii. NaHCO3, MeOH±H2O, re¯ux, 1 h, two steps, 87.8%.

350
Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
was deprotected with the similar procedures as in the
case of sugiol to a€ord 5,6-dehydrosugiol (20)12,21,23
(96.6%), which was identical with the natural com-
pound (Scheme 3).
with mCPBA in chloroform a€orded the crude epoxide,
which was further treated with p-toluenesulfonic acid in
re¯uxing chloroform to give 21 in 61.4% yield.27 The
demethylation of 21 with boron tribromide in dichloro-
methane a€orded a phenol 22 (60.6%), which was
reduced with lithium aluminum hydride to give 6b-
hydroxyferruginol (23)24 (80.2%) whose spectral data
were identical in every respect to the natural 23.
The third route (C)
6b-Hydroxyferruginol (23)24 and taxodione (25)12,16,25
were synthesized from 3 as follows. The oxidation of 3
Oxidation of the phenol at C-11 of 23 with PBO in
chloroform yielded intermediate 24 (72.4%)27 whose
benzoyl group was removed reductively with lithium
aluminum hydride and subsequent oxidation of the
crude catechol using the Jones' reagent a€orded
taxodione (25)12,16,25 in quantitative yield (Scheme 4).
Antibacterial activities
Antibacterial activities against MRSA and VRE of the
synthesized abietane diterpenes and their derivatives
were then evaluated. The minimum inhibitory con-
centrations (MIC) of synthesized phenolic diterpenes
and their related compounds against MRSA and VRE
were measured (Tables 1 and 2). Compounds in Table 1
exhibited weaker MIC against MRSA and VRE,
whereas compounds in Table 2 indicated stronger
activity. The MIC of the potent compounds were eval-
uated against further 2 species of MRSA and 2 species
of VRE. In Table 2, all compounds showed comparable
activities against 3 species of both bacteria, MRSA and
VRE, respectively. Phenols at C-12 showed more potent
activity than the methyl ethers (comparing 4 and 5, 21
and 22). Catechol 12 showed strikingly increased activ-
ity compared with its ester 11, the MIC reduced from
128 mg/mL to 6 mg/mL for MRSA (664); 128 mg/mL to
8 mg/mL for VanC, respectively. But methyl carnosoate
(26), which has catechol in C ring together with ester
carbonyl group at C-20 position, isolated from Salvia
ocinalis,28 showed weaker activity. In Table 2, deme-
thylcryptojaponol (12), salvinolone (14), 12-hydroxy-
abieta-8,11,13-trien-6-one (22), 6b-hydroxyferruginol
(23) and taxodione (25) showed potent activity against
Scheme 3. Reagents and conditions: (a) i. BH3, THF, rt, 12 h; ii.
H2O2±30%NaOH, rt, 6 h, two steps, 72%; (b) Jones' reagent, acetone,
0 ꢀC, 20 min, 85.2%; (c) EtSH, NaH, DMF, 120 ꢀC, 3 h, 98.7%; (d)
SO2Cl2, CCl4, rt, 20 h, 97.7%; (e) LiCl, pyridine, 110 ꢀC, 5 h, 85.9%;
(f) EtSH, NaH, DMF, 110 ꢀC, 3 h, 96.6%.
Scheme 4. (a) (i) mCPBA, CHCl3, 3±8 ꢀC, 4.5h; (ii) TsOH, CHCl3, re¯ux, 2 h, two steps, 61.4%; (b) BBr3, CH2Cl2, 20ꢀC, 2.5 h, 60.6%; (c) LiAlH4, THF,
re¯ux, 1 h, 80.2%; (d) BPO, CHCl3, 35ꢀC, 48 h, 72.4%; (e) (i) LiAlH4, THF, re¯ux, 1.5 h; (ii) Jones' reagent, acetone, 0ꢀC, 5 min, two steps, 97.9%.

Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
351
both bacteria with MIC of 4±10 mg/mL for MRSA and
with MIC of 4±16 mg/mL for VRE, respectively. Qui-
none methide, 11-hydroxy-12-oxo-7,9(11),13-abieta-
triene (7), showed the most potent activity (0.5±1 mg/mL
of MIC) against both MRSA and VRE. Royleanone
(9), which has para-quinone group at C-11 and C-14
position, exhibited weaker antimicrobial activity. Oxi-
dation at C-6 increased the activity (by comparison of
5 with 22 and 23, 6 with 24), whereas oxidation at C-7
strikingly decreased the activity (by comparison
between 17 and 5, between 11 and 10).
ruginol and (Æ)-ferruginol. It is interesting that
unnatural (À)-ferruginol had the most potent activity of
the three against both MRSA and VRE. Evans reported
that racemic ferruginol (5) showed MIC of 8 mg/mL
against their MRSA and totarol was about 4 times more
active than racemic 5 against their MRSA with 2 mg/mL
of MIC.2 In our results, natural ferruginol and racemic
ferruginol indicated very weaker activity, with 125 mg/
mL of MIC for MRSA(664) at least. These di€erences may
be attributed to the di€erence of the strain of the tested
MRSA. Quinone methide 7 showed stronger activity
(0.5±1 mg/mL of MIC) compared to vancomycin with
about 2±4 times against MRSA and 30±500 times against
VRE. This shows the high potential of quinone methide 7
for disinfectant or ointment for MRSA and VRE.
From these results, we found that the structure require-
ments for potent activity can be summarized in three
types: (a) quinone methides, (b) catechol with carbonyl
function at C-7, (c) alcohol or ketone at C-6 of ferrugi-
nol. We also found that most compounds showed com-
parable activity against both bacteria, MRSA and VRE.
As Evans reported that recemic ferruginol (5) showed
relatively strong activity against MRSA, we evaluated
anti-MRSA activity of the three previously synthesized
ferruginols, natural (+)-ferruginol, unnatural (À)-fer-
At present, the antibacterial mechanism of tested com-
pounds is not clear; further studies are needed to
identify the activity modes.
Conclusion
Variously oxidized 12 natural abietans, 6,7-dehy-
droferrugiol methyl ether (3), ferruginol (5) (four steps,
66.5%), 11-hydroxy-12-oxo-7,9(11),13-abietatriene (7)
(six steps, 7.2%), royleanone (9) (seven steps, 17.1%),
demethylcryptojaponol (12) (eight steps, 23.1%), salvi-
nolone (14) (nine steps, 20.1%), sugiol methyl ether (16)
(four steps, 43.3%), sugiol (17) (®ve steps, 41.9%), 5,6-
dehydrosugiol methyl ether (19) (six steps, 36.3%), 5,6-
dehydrosugiol (20) (seven steps, 35.1%), 6b-hydro-
xyferruginol (23) (®ve steps, 21.1%) and taxodione (25)
(seven steps, 14.9%) were synthesized eciently from
the common intermediate 3 which was synthesized via
polyene cyclization. Syntheses of 7, 12, 14 and 20 were
®rst performed in this report. Anti-MRSA and anti-
VRE activities of natural abietanes and their derivatives
were evaluated. Taxodione 25, phenols (22 and 23) and
catechols (12 and 14) showed potent activity with MIC
of 4±10 mg/mL against MRSA and 4±16 mg/mL against
VRE. (À)-Ferruginol showed stronger activity than
natural (+)-ferruginol. Quinone methide 7 had the
most potent activity with MIC of 0.5±1 mg/mL against
MRSA and 0.5±1 mg/mL against VRE, suggesting the
high potential of 7 for disinfectant or ointment against
MRSA and VRE.
Table 1. MIC of synthesized phenolic diterpenes and their related
compounds with weaker activity against MRSA and VRE
Strains, MIC (mg/mL)
Compounds
MRSA664
VanC
1
2
64
64
128
128
3
4
6
8
>128
>64
>64
>64
32
64
128
64
>128
>128
>128
>128
>64
>128
>64
>128
32
>128
>64
>64
>64
>64
64
9
10
11
13
15a
15b
16
17
18
19
20
21
24
26
128
128
>128
>128
>128
>128
>64
>128
>64
>128
>64
>128
>128
Table 2. MIC of synthesized phenolic diterpenes and related compounds with potent activity against MRSA and VRE
Strains, MIC (mg/mL)
MRSA
VRE
Compounds
MRSA996
MRSA730
MRSA664
VanA
VanB
VanC
0.5
8
16
6
16
4
16
62.5
7
12
14
22
23
25
1
4
6
4
8
1
4
6
4
8
8
2
0.5
6
8
4
8
8
0.5
1
8
16
6
16
6
128
8
16
4
8
4
256
10
2
Vancomycin
5:(Æ)-Ferruginol
(+)-Ferruginol
(À)-Ferruginol
2
125
>125
62.5
>125
31.3

352
Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
Experimental
was ®ltered through Celite and the solution was evapo-
rated. The residue was chromatographed on a silica gel
column with hexane±EtOAc to give (421 mg,
General
4
NMRspectra 29 were measured on a JEOL JNM-EX270
spectrometer (1H: 270 MHz; 13C: 67.8 MHz) and a
JEOL JNM AL400 (1H: 400 MHz; 13C: 100 MHz) for
samples in CDCl3, C5D5N or DMSO-d6 containing tet-
ramethylsilane as internal standard, J-values in Hz. IR
spectra were measured on a JEOL JIR-WINSPEC
50 infrared spectrometer, UV spectra on a JASCO
UVDEC-460 spectrometer. Mass spectra were recorded
on a JEOL JMS-SX102A spectrometer. Melting points
(mp) were measured on a MEL-TEMP (Laboratory
Device) and were uncorrected. TLC was carried out on
Kiesel-gel GF254 (0.25 mm thickness). Silica gel 60 (70±230
mesh ASTM) was used for column chromatography.
1.403 mmol, 98.3%) as pale yellow oil: 1H NMR
(CDCl3, 400 MHz) d 6.83 (1H, s), 6.72 (1H, s), 3.78 (3H,
s), 3.21 (1H, sept, J=6.8 Hz), 2.88±2.73 (2H, m), 2.25
(1H, br d, J=12.8 Hz), 1.87±1.21 (8H, m), 1.20 (3H, s),
1.18 (3H, d, J=6.8 Hz), 1.17 (3H, d, J=6.8 Hz), 0.94
(3H, s) 0.92 (3H, s); 13C NMR(CDCl , 67.8 MHz) d
3
154.83, 147.95, 133.99, 126.79, 126.29, 106.47, 55.62,
50.53, 41.76, 38.98, 37.92, 33.54, 33.43, 29.93, 26.5À21,
24.94, 23.02, 22.80, 21.74, 19.47, 19.34; IR(NaCl) cm
2958, 1614, 1500, 1463, 1249, 1207, 1164, 1066, 1045,
892, 848; EIMS m/z (% rel. int.) 300 (M+, 89), 285
(100), 257 (9), 243 (20), 229 (16), 215 (35), 203 (32), 201
(35), 189 (38), 163 (19), 129 (18), 69 (16), 55 (15);
HREIMS m/z calcd for C21H32O 300.2453, found
300.2431; UV lmax nm (EtOH, E) 205 (4.22Â103), 280
(3.59Â102).
7ꢀ-Carboxyabieta-8,11,13-trien-12-methyl ether (2).
Under argon, a mixture of 1 (252 mg, 0.834 mmol) and
AlCl3 (550 mg) in dichloromethane (12 mL) was stirred
for 10 min and then 2-chloropropane (2.9 mL,
13.4 mmol) was added to the mixture. The mixture was
further stirred for 40 h at 40 ꢀC. The reaction was stop-
ped by addition of saturated aqueous NaHCO3. The
mixture was extracted with ethyl acetate (EtOAc). The
organic extract was washed with brine, dried over
MgSO4 and evaporated. The residue was chromato-
graphed on a silica gel column with hexane±EtOAc to
Ferruginol (5). A solution of 4 (299 mg, 0.966 mmol) and
boron tribromide (0.35 mL) in dichloromethane (10 mL)
was stirred at 0±5 ꢀC for 2 h under argon. The solution
was then poured into water and extracted with EtOAc.
The combined solution was washed with brine, dried
and then evaporated to dryness. The crude product was
puri®ed by column chromatography (silica gel, hexane±
EtOAc) to give ferruginol (5) (262 mg, 0.916 mmol,
94.9%) as oil.
1
give 2 as oily solid (232 mg, 0.674 mmol, 80.9%): H
NMR(CDCl , 270 MHz) d 6.99 (1H, s), 6.73 (1H, s),
3
3.84 (1H, d, J=6.3 Hz), 3.79 (3H, s), 3.21 (1H, sept,
J=6.8 Hz), 2.28±2.18 (2H, m), 2.02±1.89 (1H, m), 1.78±
1.57 (3H, m), 1.51±1.36 (2H, m), 1.33±1.23 (1H, m), 1.18
(3H, d, J=6.8 Hz), 1.16 (3H, d, J=6.8 Hz), 1.18 (3H, s),
12-Benzoyloxyabieta-8,11,13-trien-11-ol (6). Benzoyl
peroxide (279 mg, 1.153 mmol) was added to a solution
of ferruginol (5) (177 mg, 0.618 mmol) in chloroform
(5 mL) and then stirred for 7 h at room temperature
until the disappearance of starting material with mon-
itoring by NMR(because of their similar polarity). The
reaction was stopped by addition of 0.5 M aqueous
sodium thiosulfate (3 mL) and the mixture was extrac-
ted with ethyl acetate. The organic layer was washed
with brine, dried and evaporated. The residue was
chromatographed on a column of silica gel with hexane±
EtOAc to a€ord 6 (179 mg, 0.441 mmol, 71.4%) as
crystals: mp 133 ꢀC; 1H NMR(CDCl 3, 400 MHz) d 8.23
(2H, d, J=7.1 Hz), 7.67 (1H, t, J=7.4 Hz), 7.53 (2H, t,
J=7.5 Hz), 6.60 (1H, s), 5.17 (1H, s), 3.11 (1H, br d,
J=12.4 Hz), 2.89±2.82 (3H, m), 1.82 (1H, br d,
J=12.7 Hz), 1.34 (3H, s), 1.19 (3H, d, J=6.8 Hz), 1.16
(3H, d, J=6.8 Hz), 0.96 (3H, s), 0.93 (3H, s); 13C NMR
(CDCl3, 100 MHz) d 164.91, 145.63, 137.41, 135.61,
134.77, 134.75, 133.93, 130.33, 130.29, 130.27, 128.73,
128.66, 118.53, 52.81, 41.51, 39.60, 39.42, 36.55, 33.76,
32.90, 27.65, 23.09, 23.00, 22.21, 20.17, 19.43, 19.18; IR
(KBr) cmÀ1 3453, 2960, 1743, 1708, 1452, 1425, 1265,
1060, 1024, 711; EIMS m/z (% rel. int.) 406 (M+, 23),
215 (9), 189 (12), 128 (10), 106 (25), 105 (100), 77 (61),
51 (11); HREIMS m/z calcd for C27H34O3 406.2508,
found 406.2484; UV lmax nm (EtOH, E) 222 (3.73Â104),
230 (2.10Â104), 272 (6.64Â103).
0.94 (3H, s), 0.91 (3H, s); 13C NMR(CDCl , 100 MHz)
3
d 180.07, 156.00, 148.65, 134.31, 127.65, 122.05, 106.34,
55.27, 46.79, 44.24, 41.46, 38.54, 38.02, 33.22, 33.01,
29.80, 26.62, 24.85, 22.84, 22.65, 21.64, 19.38; IR(KBr)
cmÀ1 3474, 2929, 1706, 1500, 1459, 1253, 1178; EIMS
m/z (% rel. int.) 344 (M+, 10), 331 (30), 301 (100), 287
(39), 259 (36), 243 (38), 217 (50), 205 (39), 175 (69), 173
(45), 167 (40), 70 (49); HREIMS m/z calcd for C22H32O3
344.2351, found 344.2338; UV lmax nm (EtOH, E) 207
(1.89Â104), 277 (2.57Â103), 285 (2.45Â103).
6,7-Dehydroferruginol methyl ether (3). A mixture of 2
(233 mg, 0.677 mmol), lead tetraacetate (LTA, 1 g) and
Cu(OAc)2 (135 mg) in quinoline (10 mL) was stirred at
125 ꢀC for 16 h under argon. The mixture was acidi®ed
with 1 M HCl and was then extracted with ethyl acetate.
The organic layer was washed with brine, dried and
evaporated. The residue was chromatographed on a
column of silica gel with hexane±EtOAc to yield 3 as
yellow oil (176 mg, 0.592 mmol, 87.4%): IR(NaCl)
cmÀ1 2958, 1714, 1604, 1500, 1463, 1051, 892, 850, 767;
EIMS m/z (% rel. int.) 298 (M+, 100), 283 (30), 241
(45), 216 (65), 213 (43), 199 (34), 173 (34); HREIMS m/z
calcd for C21H30O 298.2297, found 298.2303; UV lmax
nm (EtOH, E) 221 (4.66Â103), 279 (1.95Â103).
11-Hydroxy-12-oxo-7,9(11),13-abietatriene (7). A solu-
tion of DIBAL in toluene (0.096 mmol) was added to a
solution of 6 (10 mg, 0.024 mmol) in THF (2 mL) under
argon and the solution was stirred at À15 ꢀC for 3 h.
Ferruginol methyl ether (4). A mixture of Pd/C (80 mg)
and 3 (425 mg, 1.426 mmol) in EtOAc (10 mL) was stir-
red at room temperature under H2 for 24 h. The mixture

Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
353
The reaction mixture was extracted with EtOAc±water.
The organic layer was washed with brine, dried and
evaporated to dryness. The residue was oxidized by air
and then chromatographed on a silica gel column with
hexane±EtOAc to give 7 (1.1 mg, 0.004 mmol, 15.1%) as
oil.
139.66, 139.46, 138.45, 138.22, 135.68, 133.69, 130.15,
129.14, 128.69, 124.60, 51.61, 40.95, 39.56, 36.89, 33.72,
32.44, 27.35, 22.97, 22.07, À211.98, 21.48, 20.44, 20.32,
19.28, 19.16; IR(KBr) cm
2962, 1770, 1731, 1600,
1475, 1415, 1369, 1189, 1085, 1014, 917, 879, 709; EIMS
m/z (% rel. int.) 448 (M+, 37), 408 (27), 371 (27), 341
(31), 238 (31), 106 (100), 66 (26); HREIMS m/z calcd for
C29H36O4 448.2614, found 448.2581; UV lmax nm
(EtOH, E) 216 (2.35Â104), 230 (2.49Â104).
12-Benzoyloxyabieta-8,12-dien-11,14-dione (8). meta-
Chloroperbenzoic acid (29 mg, 0.168 mmol) was added
to a solution of 6 (34 mg, 0.084 mmol) in dichloro-
methane (3 mL) and the solution was stirred at room
temperature for 12 h. The reaction was stopped by
addition of aqueous 5% Na2S2O3 solution (3 mL). The
mixture was extracted with EtOAC and the organic
layer was washed with 5% aqueous NaOH and brine
successively, dried and evaporated. The residue was
chromatographed on a column of silica gel with hexane±
EtOAc to yield 8 (14ꢀmg, 0.036 mmol, 42.3%) as yellow
11-Acetoxy-12-benzoyloxyabieta-8,11,13-trien-7-one
(11). Chromium trioxide (57 mg, 0.57 mmol) was added
to a solution of 10 (126 mg, 0.281 mmol) in acetic acid
(3 mL), and allowed to stand at room temperature for
8 h. The reaction mixture was poured into water and
was extracted with EtOAc. The organic layer was
washed with brine, dried and evaporated. The crude
product was puri®ed by column chromatography of
silica gel with hexane±EtOAc to a€ord 11 (86 mg,
0.186 mmol, 65.9%), which was recrystallized from
EtOAc to give colorless crsytals: mp 160±161 ꢀC; 1H
NMR(CDCl 3, 400 MHz) d 8.19 (2H, d, J=7.2 Hz), 8.06
(1H, s), 7.69 (1H, t, J=7.6 Hz), 7.56 (2H, t, J=7.2 Hz),
2.95 (1H, sept, J=6.4 Hz), 2.74 (1H, dd, J=17.8,
4.1 Hz), 2.63 (1H, dd, J=17.8, 13.6 Hz), 1.93 (3H, s),
1.28 (3H, s), 1.27 (3H, d, J=6.4 Hz), 1.23 (3H, d,
J=6.4 Hz), 0.95 (6H, s); 13C NMR(CDCl 3, 100 MHz) d
197.84, 168.03, 164.29, 145.22, 145.08, 144.96, 144.88,
140.51, 140.12, 134.13, 130.74, 130.23, 128.91, 128.55,
124.16, 49.60, 40.70, 40.48, 37.29, 35.75, 33.61, 32.97,
27.66, 23.06, 22.79, 21.47, 20.37, 20.31, 19.02; IR(KBr)
cmÀ1 2964, 1774, 1747, 1689, 1452, 1247, 1197, 1178,
1058, 1024, 711; EIMS m/z (% rel. int.) 462 (M+, 8),
423 (5), 275 (8), 238 (5), 194 (4), 123 (6), 106 (100), 93
(6), 84 (8), 78 (14), 58 (8), 56 (7); HREIMS m/z calcd for
C29H34O5 462.2406, found 462.2451; UV lmax nm
(EtOH, E) 238 (3.55Â104).
1
crystals: mp 196±197 C; H NMR(CDCl 3, 400 MHz) d
8.15 (2H, dd, J=7.9, 1.6 Hz), 7.65 (1H, br t, J=7.6 Hz),
7.51 (2H, t, J=7.5 Hz), 3.18 (1H, sept, J=6.9 Hz), 2.74
(1H, dd, J=20.2, 5.3 Hz), 2.39±2.29 (1H, m), 1.88 (1H,
dd, J=13.2, 7.2 Hz), 1.28 (3H, s), 1.23 (3H, d,
J=6.9 Hz), 1.20 (3H, d, J=6.9 Hz), 0.94 (3H, s), 0.89
(3H, s); 13C NMR(CDCl , 100 MHz) d 187.28, 163.98,
3
134.01, 130.43, 128.65, 128.15, 51.49, 41.37, 38.76,
36.22, 33.59, 33.51, 26.04, À215.08, 21.84, 20.59, 20.32,
18.91, 17.49; IR(KBr) cm
2925, 1741, 1664, 1646,
1452, 1236, 1047, 1004, 707; EIMS m/z (% rel. int.) 420
(M+, 8), 324 (5), 315 (5), 270 (12), 105 (100), 77 (21), 69
(8), 55 (7); HREIMS m/z calcd for C27H32O4 420.2301,
found 420.2288; UV lmax nm (EtOH, E) 233 (1.86Â104),
263 (1.99Â104), 333 (3.36Â102).
Royleanone (9). A solution of 8 (14 mg, 0.033 mmol) and
NaHCO3 (43 mg) in MeOH:H2O (6:1, 7 mL) was
re¯uxed for 1.5 h. The reaction mixture was extracted
with EtOAc, and the organic layer was washed with
brine, dried and evaporated. The crude product was
chromatographed on a column of silica gel with hexane±
EtOAc to give 9 (9 mg, 0.028 mmol, 85%) as pale yellow
Demethylcryptojaponol (12). Sodium bicarbonate
(27 mg, 0.321 mmol) was added to a solution of 11
(11 mg, 0.023 mmol) in MeOH:H2O (4:1, 5 mL) under
argon. After re¯uxing for 1.5 h, the reaction mixture
was extracted with EtOAc and the organic layer was
washed with brine, dried and evaporated. The residue
was chromatographed on a silica gel column with hex-
crystals: mp 182±183 ꢀC; IR(KBr) cm
3332, 2964,
À1
2919, 2850, 1735, 1652, 1648, 1604, 1459, 1405, 1376,
1253, 736; EIMS m/z (% rel. int.) 316 (M+, 100), 301
(36), 231 (25), 220 (29), 219 (31), 205 (32), 83 (29), 69
(43), 55 (42); HREIMS m/z calcd for C20H28O3
316.2038, found 316.2061; UV lmax nm (EtOH, E) 271
(1.11Â104), 412 (4.5Â102).
ane±EtOAc to yield 12 (7 mg, 0.022 mmol, 96.3%) as
1
pale yellow solid: H NMR(CDCl 400 MHz) d 7.63
3,
(1H, s), 5.65 (1H, s), 5.63 (1H, s), 3.10 (1H, br d,
J=13.2 Hz), 3.02 (1H, sept, J=6.8 Hz), 2.64 (1H, dd,
J=17.1, 3.2 Hz), 2.54 (1H, dd, J=17.1, 14.1 Hz), 1.88
(1H, dd, J=14.1, 3.2 Hz), 1.81±1.73 (1H, m), 1.64±1.43
(4H, m), 1.40 (3H, s), 1.29 (3H, d, J=6.8 Hz), 1.26 (3H,
d, J=6.8 Hz), 0.98 (3H, s), 0.94 (3H, s); 13C NMR
(CDCl3, 100 MHz) d 198.86, 146.09, 140.93, 138.48,
131.52, 125.29, 117.94, 50.22, 41.07, 40.19, 36.84, 35.62,
33.53, 33.16, 27.41, 22.55, 22.39, 21.60, 19.11, 18.72.
11 - Acetoxy - 12 - benzoyloxyabieta - 8,11,13- triene (10).
Isopropenyl acetate (0.837 mL, 7.7 mmol) and TsOH
(17 mg) were added to a solution of 6 (310 mg,
0.763 mmol) in toluene (5 mL). After re¯uxing for 5 h,
the reaction mixture was concentrated and the mixture
was chromatographed on silica gel with hexane±EtOAc
to a€ord 10 (262 mg, 0.585 mmol, 76.7%), which was
recrystallized from EtOAc to give colorless crystals: mp
178±179 ꢀC; 1H NMR(CDCl 3, 270 MHz) d 8.19 (2H, d,
J=7.6 Hz), 7.66 (1H, t, J=7.4 Hz), 7.52 (2H, t,
J=7.9 Hz), 6.92 (1H, s), 2.94±2.78 (3H, m), 1.89 (3H, s),
1.38 (3H, s), 1.21 (3H, d, J=7.2 Hz), 1.16 (3H, d,
J=7.2 Hz), 0.94 (3H, s), 0.89 (3H, s); 13C NMR
(CDCl3, 67.8 MHz) d 168.84, 164.62, 141.09, 140.86,
6-Chloro-11-acetoxy-12-benzoyloxyabieta-8,11,13-trien-
7-one (13). SO2Cl2 (0.04 mL) was added dropwise to a
solution of 11 (37 mg, 0.079 mmol) in CCl4 (1.5 mL),
and the solution was stirred at 60 ꢀC for 40 h. The reac-
tion mixture was concentrated to give the crude product
which was chromatographed on a silica gel column with

354
Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
hexane±EtOAc to yield 13 (37 mg, 0.075 mmol, 94.9%)
1
(57), 213 (60), 192 (88), 171 (41), 69 (25); HREIMS m/z
calcd for C21H32O2 316.2402, found 316.2386; UV lmax
nm (EtOH, E) 210 (2.12Â103), 280 (2.97Â103). 15b (7a-
as colorless oily solid: H NMR(CDCl , 400 MHz) d
3
8.19±8.16 (2H, m), 7.74 (1H, s), 7.69 (1H, t, J=7.2 Hz),
7.56 (2H, t, J=7.6 Hz), 4.61±4.56 (1H, m), 2.97 (1H,
sept, J=7.2 Hz), 2.32 (1H, t, J=4.1 Hz), 2.13±2.10 (1H,
m), 1.98 (3H, s), 1.27 (3H, d, J=7.2 Hz), 1.25 (3H, d,
J=7.2 Hz), 1.21 (3H, s), 1.20 (3H, s), 1.12 (3H, s); 13C
NMR(CDCl 3, 100 MHz) d 193.83, 168.07, 164.40,
145.34, 142.23, 141.25, 140.98, 138.78, 134.22, 131.43,
130.24, 130.20, 128.93, 128.36, 124.94, 56.34, 56.12,
41.64, 41.43, 37.59, 36.56, 35.12, 27.76,À125.69, 25.13,
H): mp 142±143 ꢀC; 1H NMR(CDCl , 400 MHz) d 7.16
3
(1H, s), 6.72 (1H, s), 5.00 (1H, br s), 4.99 (1H, dd,
J=3.6, 1.6 Hz), 3.80 (3H, s), 3.22 (1H, sept, J=6.8 Hz),
2.47 (1H, br d, J=13.6 Hz), 2.22 (1H, br d, J=12.6 Hz),
1.81±1.59 (4H, m), 1.52±1.35 (3H, m), 1.31±1.22 (1H,
m), 1.21 (3H, d, J=6.8 Hz), 1.18 (3H, d, J=6.8 Hz),
1.16 (3H, s), 1.01 (3H, s), 0.95 (3H, s); 13C NMR
(CDCl3, 100 MHz) d 157.41, 150.40, 134.47, 128.97,
121.88, 105.94, 81.53, 55.34, 44.43, 41.49, 38.43, 38.29,
33.21, 33.09, 26.58, 24.11, 23.21, 22.90, 22.53, 21.77,
22.92, 22.57, 20.36, 18.84; IR(NaCl) cm
2964, 2931,
2871, 1774, 1745, 1700, 1452, 1369, 1307, 1149, 1079,
904, 860, EIMS m/z (% rel. int.) 497 (M+, 27), 422 (32),
380 (36), 225 (43), 210 (37), 182 (38), 154 (39), 130 (39),
125 (44), 106 (100), 96 (51), 56 (89); HREIMS m/z calcd
for C29H33ClO5 496.2017, found 496.2012; UV lmax nm
(EtOH, E) 231 (1.92Â104), 259 (1.00Â104).
À1
19.33; IR(KBr) cm
3415, 2998, 1614, 1571, 1504,
1471, 1162, 1035, 943, 856, 823, 755; EIMS m/z (% rel.
int.) 316 (63), 301 (100), 275 (21), 243 (15), 233 (15), 219
(17), 205 (13), 194 (13); HREIMS m/z calcd for
C21H32O2 316.2402, found 316.2361; UV lmax nm
(EtOH, E) 230 (6.12Â103), 279 (1.33Â103).
Salvinolone (14). Lithium chloride (8 mg, 0.19 mmol)
was added to a solution of 13 (14.7 mg, 0.029 mmol) in
pyridine (1.5 mL) and the mixture was re¯uxed for 10 h.
The mixture was acidi®ed to acidity slightly with 1 M
HCl solution. The mixture was extracted with EtOAc
and the organic layer was washed with brine, dried and
evaporated. To the residue, a solution of sodium bicar-
bonate (26 mg, 0.309 mmol) in MeOH:H2O (6:1, 5 mL)
was added and the mixture was re¯uxed for 1 h under
argon. The reaction mixture was extracted with EtOAc
and the organic layer was washed with brine, dried and
evaporated. The residue was chromatographed on a
silica gel column with hexane±EtOAc to yield 14 (8 mg,
Sugiol methyl ether (16). Jones' reagent (0.2 mL) was
added to a solution of alcohols 15a and 15b (92 mg,
0.291 mmol) in acetone (10 mL) and the mixture was
allowed to stand in an ice bath for 20 min. The mixture
was extracted with EtOAc and the organic layer was
washed with brine and dried. The organic layer was
concentrated under vacuum and the crude product was
chromatographed on a silica gel column with hexane±
EtOAc to yield 16 (78 mg, 0.248 mmol, 85.2%À)1as col-
orless crystals: mp 124±125 ꢀC; IR(KBr) cm
3030,
2919, 1672, 1594, 1562, 1494, 1305, 1274, 1218, 1187,
1029, 912, 840; HREIMS m/z calcd for C21H30O2
314.2246, found 314.2258.
0.025 mmol, 87.8%) as oily solid: 13C NMR(CDCl ,
3
100 MHz) d 185.72, 175.38, 144.59, 141.32, 137.33,
132.52, 124.01, 123.42, 115.68, 42.24, 40.45, 38.22,
34.35, 33.16, 29.45, 27.46, 24.94, 22.71, 22.56, 18.81.
Sugiol (17). NaH (65 mg, 2.7 mmol) was added to a
solution of EtSH (0.2 mL, 2.7 mmol) in DMF (3 mL)
under argon and stirred for 20 min at ambient tempera-
ture. To the mixture, 16 (34 mg, 0.108 mmol) in DMF
(2 mL) was added and the mixture was stirred for a
further 3 h at 120 ꢀC. The reaction was stopped by
addition of a saturated solution of NH4Cl (1 mL) and
the mixture was extracted with EtOAc and the organic
layer was washed with brine and dried. The organic
layer was concentrated and the residue was puri®ed by
column chromatography (silica gel, hexane±EtOAc) to
a€ord 17 (32 mg, 0.107 mmol, 98.7%) as colorless crys-
tals: mp 238±239 ꢀC; HREIMS m/z calcd for C20H28O2
300.2089, found 300.2084; UV lmax nm (EtOH, E) 233
(5.01Â103), 290 (5.57Â103).
12-Methoxyabieta-8,11,13-trien-7-ol (15a and 15b). Bor-
.
ane±tetrahydrofuran complex solution (BH3 THF 1 M,
5.29 mmol) was added to a solution of 3 (157 mg,
0.527 mmol) in THF (20 mL) under argon, and the
mixture was stirred for 12 h at room temperature. Water
(6 mL), 30% NaOH (12 mL) and 30% H2O2 (12 mL)
were added to the reaction mixture, and the mixture was
stirred for a further 6 h at ambient temperature. The
mixture was extracted with EtOAc and the organic layer
was washed with brine, dried and evaporated. The crude
product was puri®ed by column chromatography (silica
gel, hexane±EtOAc) to give 12-methoxyabieta-8,11,13-
trien-7a-ol (15a) as a pale yellow oil and 12-methoxy-
abieta-8,11,13-trien-7b-ol (15b) as colorless crystals
(15a:15b=1:1, total 120 mg, 0.379 mmol, 72.0%). 15a
(7b-H): 1H NMR(CDCl 3, 270 MHz) d 7.14 (1H, s), 6.71
(1H, s), 4.78 (1H, br s), 3.85 (1H, d, J=4.4 Hz), 3.80
(3H, s), 3.23 (1H, sept, J=6.8 Hz), 2.24 (1H, br d,
J=12.3 Hz), 2.02±1.25 (8H, m), 1.21 (3H, d, J=6.8 Hz),
1.18 (3H, d, J=6.8 Hz), 1.14 (3H, s), 0.98 (3H, s), 0.93
6-Chlorosugiol methyl ether (18). A solution of SO2Cl2
(0.3 mL) in CCl4 (1 mL) was added dropwise to a solu-
tion of 16 (55 mg, 0.175 mmol) in CCl4 (6 mL) under
argon and the solution was allowed to react at ambient
temperature for 20 h. After the reaction was stopped by
addition of water, the mixture was washed with aqueous
saturated NaHCO3 solution, and the organic layer was
extracted with EtOAc, washed with brine and dried.
The organic phase was concentrated to give a crude
yellow solid which was chromatographed on a silica gel
column with hexane±EtOAc to yield 18 (59 mg,
0.171 mmol, 97.7%) as pale yellow crystals: mp 108±
122 ꢀC; 1H NMR(CDCl 3, 400 MHz) d 7.71 (1H, s), 6.72
(3H, s); 13C NMR(CDCl , 67.8 MHz) d 156.66, 148.33,
3
134.87, 128.28, 127.45, 105.83, 68.01, 55.38, 44.61,
41.60, 38.59, 38.28, 33.24, 33.07, 28.77,À126.66, 24.04,
22.94, 22.58, 21.76, 19.39; IR(NaCl) cm
3453, 2958,
1714, 1602, 1500, 1463, 1363, 1243, 1047, 852; EIMS m/
z (% rel. int.) 316 (M+, 100), 298 (57), 273 (64), 241

Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
355
(1H, s), 4.61 (1H, d, J=9.5 Hz), 3.91 (3H, s), 3.25 (1H,
sept, J=6.8 Hz), 2.11 (1H, d, J=9.5 Hz), 1.22 (3H, s),
1.22 (3H, d, J=6.8 Hz), 1.20 (3H, d, J=6.8 Hz), 1.17
with hexane±EtOAc to give 21 (208 mg, 0.662 mmol,
1
61.4%) as yellow oil: H NMR(CDCl , 400 MHz) d
3
6.85 (1H, s), 6.79 (1H, s), 3.83 (3H, s), 3.58 (1H, d,
J=21.4 Hz), 3.51 (1H, d, J=21.4 Hz), 3.26 (1H, sept,
J=6.8 Hz), 2.42 (1H, s), 2.31 (1H, br d, J=9.5 Hz),
1.78±1.64 (3H, m), 1.42 (1H, br d, J=14.6 Hz), 1.31
(3H, s), 1.30±1.25 (1H, m), 1.20 (3H, d, J=6.8 Hz), 1.18
(3H, d, J=6.8 Hz), 1.16 (3H, s), 1.08 (3H, s); 13C NMR
(CDCl3, 68.7 MHz) d 210.02, 155.53, 146.86, 135.26,
125.78, 123.81, 105.72, 62.56, 55.61, 44.64, 42.85, 40.67,
(3H, s), 1.11 (3H, s); 13C NMR(CDCl , 67.8 MHz), d
3
193.24, 161.66, 153.81, 135.79, 126.44, 123.75, 103.30,
59.66, 56.49, 55.52, 42.75, 38.80, 37.35, 35.46, 34.87,
À1
26.65, 26.13, 22.53, 22.37, 18.64; IR(KBr) cm
2923,
1687, 1606, 1567, 1496, 1469, 1255, 1174, 1049, 908,
858, 642; EIMS m/z (% rel. int.) 350 (M+2, 17), 348
(M+, 49), 333 (40), 299 (19), 229 (21), 217 (100), 215
(21), 128 (18), 55 (15); HREIMS m/z calcd for
C21H29ClO2 348.1856, found 348.1854; UV lmax nm
(EtOH, E) 233 (1.08Â104), 300 (1.08Â104).
38.66, 33.01, 32.70, 26.54, 24.65, 22.92, 22.72, 21.64,
À1
18.79; IR(NaCl) cm
2960, 1718, 1600, 1498, 1457,
1249, 1049; EIMS m/z (% rel. int.) 314 (M+, 21), 313
(30), 285 (66), 259 (100), 258 (84), 243 (48), 229 (31), 217
(59), 215 (26), 187 (21), 165 (19), 128 (23), 69 (24);
HREIMS m/z calcd for C21H30O2 314.2246, found
314.2242; UV lmax nm (EtOH, E) 216 (1.78Â104), 243
(6.43Â103), 276 (1.11Â104), 333 (7.58Â103).
5,6-Dehydrosugiol methyl ether (19). To a solution of 18
(40 mg, 0.115 mmol) in pyridine (6 mL), lithium chloride
(244 mg) was added and the mixture was stirred at
110 ꢀC for 5 h. The reaction mixture was acidi®ed with
1 M HCl solution and was extracted with EtOAc. The
organic layer was washed with brine and dried. The
organic phase was concentrated and the crude product
was puri®ed by column chromatography (silica gel,
hexane±EtOAc) to give 19 (31 mg, 0.099 mmol, 85.9%)
as white crystals: mp 167±168 ꢀC.
12-Hydroxyabieta-8,11,13-trien-6-one (22). To a solu-
tion of 21 (297 mg, 0.945 mmol) in dichloromethane
(10 mL), boron tribromide (0.27 mL) was added and the
solution was stirred for 2.5 h at 20 ꢀC under argon. The
reaction was stopped by addition of water (1 mL) and
the mixture was extracted with EtOAc. The organic
layer was washed with brine, dried and evaporated. The
residue was concentrated and chromatographed on a
silica gel column with hexane±EtOAc to a€ord 22
(172 mg, 0.573 mmol, 60.6%) as crystals: mp 134±
135 ꢀC; 1H NMR(CDCl 3, 400 MHz) d 6.84 (1H, s), 6.76
(1H, s), 5.72 (1H, br s), 3.57 (1H, d, J=21.6 Hz), 3.56
(1H, d, J=21.6 Hz), 3.19 (1H, sept, J=6.7 Hz), 2.41
(1H, s), 2.21 (1H, br d, J=10.8 Hz), 1.75±1.60 (3H, m),
1.41 (1H, br d, J=13.2 Hz), 1.31 (3H, s), 1.24 (3H, d,
J=6.7 Hz), 1.23 (3H, d, J=6.7 Hz), 1.13 (3H, s),
1.08(3H, s); 13C NMR(CDCl 3, 100 MHz) d 210.88,
151.78, 147.16, 132.81, 126.03, 123.77, 110.45, 62.56,
5.6-Dehydrosugiol (20). NaH (142 mg, 5.9 mmol) was
added to a solution of EtSH (0.44 mL, 5.9 mmol) in
DMF (5 mL) under argon and the mixture was stirred
for 10 min at ambient temperature. To the mixture, 19
(74 mg, 0.237 mmol) in DMF (3 mL) was added and the
mixture was stirred for a further 3 h at 110 ꢀC. The
reaction was stopped by addition of aqueous saturated
NH4Cl (1 mL) and the mixture was treated as described
for 17 to a€ord 20 (68 mg, 0.228 mmol, 96.6%) as white
crystals: mp 274±275 ꢀC; 1H NMR(CDCl , 270 MHz) d
3
8.01 (1H, s), 6.86 (1H, s), 6.45 (1H, s), 5.74 (1H, br s),
3.19 (1H, sept, J=7.0 Hz), 2.35 (1H, br d, J=12.5 Hz),
2.05±1.94 (1H, m), 1.78±1.55 (3H, m), 1.50 (3H, s), 1.45
(1H, dd, J=14.0, 4.4 Hz), 1.34 (3H, s), 1.30 (3H, d,
J=7.0 Hz), 1.28 (3H, d, J=7.0 Hz), 1.25 (3H, s); 13C
NMR(CDCl 3, 100 MHz) d 185.46, 173.57, 158.04,
154.10, 133.76, 124.88, 124.28, 123.33, 111.05, 41.19,
40.37, 37.73, 37.56, 32.65, 29.19, 26.95, 22.58, 22.41,
18.69; EIMS m/z (% rel. int.) 298 (M+, 100), 283 (63),
255 (43), 229 (89), 213 (97), 199 (43), 187 (30),165 (22),
69 (43), 55 (21); HREIMS m/z calcd for C20H26O2
298.1933, found 298.1958.
44.62, 42.84, 40.27, 38.60, 32.97, 32.66, 26.81, 24.54,
À1
22.76, 22.59, 21.61, 18.71; IR(KBr) cm
2927, 1712,
1571, 1513, 1463, 1230, 1174, 1047, 1002, 964; EIMS m/z
(% rel. int.) 300 (M+, 89), 285 (100), 257 (45), 243 (45),
215 (38), 201 (30), 173 (26), 159 (21), 128 (23), 69 (16),
55 (16); HREIMS m/z calcd for C20H28O2 300.2089,
found 300.2088; UV lmax nm (EtOH, E) 251 (5.85Â103),
283 (8.77Â103), 333 (7.95Â103).
6ꢁ-Hydroxyferruginol (23). A mixture of 22 (67 mg,
0.223 mmol) and lithium aluminum hydride (200 mg) in
dry THF (10 mL) was re¯uxed for 1 h. The reaction
mixture was then poured into water and extracted with
EtOAc. The organic layer was washed with brine, dried
and evaporated. The residue was chromatographed on a
column of silica gel with hexane±EtOAc to give 23
(54 mg, 0.179 mmol, 80.2%) as white crystals: mp 175±
176 ꢀC; EIMS m/z (% rel. int.) 302 (M+, 51), 269 (100),
227 (23), 199 (27), 185 (14), 159 (15), 69 (11), 55 (6); UV
lmax nm (EtOH, E) 222 (7.19Â103), 280 (4.78Â103).
12-Methoxyabieta-8,11,13-trien-6-one (21). meta-Chloro-
perbenzoic acid (446 mg) was added to a solution of 3
(321 mg, 1.077 mmol) in chloroform (12 mL) in three
portions and the solution was stirred at 3ꢁ8 ꢀC for
4.5 h. After addition of aqueous 5% Na2S2O3 solution
(3 mL) to stop the reaction, the mixture was extracted
with EtOAc. The organic layer was washed with 5%
aqueous NaOH and brine successively, dried and eva-
porated. The crude product was dissolved in chloroform
(20 mL) and was re¯uxed with p-toluenesulfonic acid
(280 mg) for a further 2 h. The reaction mixture was
washed with aqueous saturated NaHCO3 solution and
was then extracted with water and EtOAc. The organic
layer was washed with brine, dried and evaporated. The
residue was chromatographed on a silica gel column
12-Benzoyloxyabieta-8,11,13-trien-6ꢁ,12-diol (24). Ben-
zoyl peroxide (66 mg, 0.273 mmol) was added to a solu-
tion of 23 (21 mg, 0.069 mmol) in dry chloroform (3 mL)
and the mixture was stirred at 35 ꢀC for 48 h. The reac-
tion was stopped by addition of 0.5 M Na2S2O3

356
Z. Yang et al. / Bioorg. Med. Chem. 9 (2001) 347±356
solution and the mixture was extracted with EtOAc.
The organic layer was washed with brine and dried. The
solvent was removed and the residue was puri®ed by
chromatography on a column of silica gel with hexane±
visible growth of bacteria, compared with the control
which had no test compound. It should be noted that the
concentration of DMSO in the medium did not a€ect
the growth of any of the microorganisms tested. The
MIC of each compound was determined at least twice.
EtOAc to yield 24 (21 mg, 0.050 mmol, 72.4%) as pale
1
yellow oil: H NMR(CDCl , 400 MHz) d 8.23 (2H, dd,
3
J=8.5, 1.5 Hz), 7.67 (1H, t, J=6.4 Hz), 7.54 (2H, t,
J=8.4 Hz), 6.62 (1H, s), 5.32 (1H, br s), 4.65 (1H, d,
J=4.0 Hz), 3.17±3.11 (2H, m), 3.03 (1H, br d,
J=12.8 Hz), 2.92±2.84 (2H, m), 1.72 (3H, s), 1.28 (3H,
s), 1.19 (3H, d, J=6.8 Hz), 1.17 (3H, d, J=6.8 Hz), 1.05
References and Notes
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128.78, 128.58, 125.36, 119.44, 65.85, 60.46, 54.33,
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Ä
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(12), 55 (15); HREIMS m/z calcd for C27H34O4
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0.039 mmol) under argon and the mixture was re¯uxed
for 1.5 h. The reaction mixture was then poured into
water and extracted with EtOAc. The organic layer was
washed with brine, dried and evaporated. The crude
product was dissolved in acetone (3 mL) and was
immediately oxidized with the Jones reagent (4 drops)
at 0 ꢀC for 5 min. The mixture was neutralized with
aqueous saturated NaHCO3 (0.5 mL) and the mixture
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1351, 1143, 906; EIMS m/z (% rel. int.) 314 (M+, 100),
286 (86), 271 (79), 253 (33), 245 (83), 243 (34), 231 (64),
229 (30), 217 (42), 215 (39), 203 (35), 189 (28), 141 (31),
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Antibacterial activities
Test organisms, three strains of MRSA (MRSA664,
MRSA730 and MRSA996) and three strains of VRE
(VanA, VanB and VanC) were obtained from Depart-
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29. As the NMRspectral data of the many natural abietanes
were recorded in C5D5N or DMSO in the literature, the NMR
spectral data in CDCl3 were recorded in this report for
convenience.
Each compound was dissolved in DMSO and diluted in
graded concentration with Mueller±Hinton broth.
Minimum inhibitory concentrations (MIC) were deter-
mined by the broth microdilution method. The over-
night broth cultures were diluted to approximately 108
CFU (colony forming units) mLÀ1 with water and fur-
ther diluted to 107 CFU mLÀ1 with water. Test inocu-
lum of 107 CFU mLÀ1 (5 mL) per spot was applied to
96-well micro-plates containing 0.1 mL of graded con-
centrations of each compound. After incubation at
37 ꢀC for 18±20 h, the MIC was de®ned as the minimum
concentration of the test compounds that resulted in no