Synthesis and inhibition studies of sulfur-substituted squalene oxide analogues as mechanism-based inhibitors of 2,3-oxidosqualene-lanosterol cyclase

Article abstract of DOI:10.1021/jm960483a

The synthesis and biological evaluation of three new sulfur-substituted oxidosqualene (OS) analogues (1-3) are presented. In these analogues, C-11, C-15, or C-18 in the OS skeleton was replaced by sulfur. The sulfur position in the OS skeleton was chosen to disrupt one or more key processes involved in cyclization: (a) the folding of the B-ring into a boat conformation, (b) the anti-Markovnikov cyclization leading to the C-ring, or (c) the formation of the D-ring during the lanosterol biosynthesis. Enzyme inhibition kinetics using homogeneous mammalian oxidosqualene cyclases (OSC) were also examined for the previously reported S-19 analogue 4. The four analogues were potent inhibitors of mammalian OSCs (IC₅₀ = 0.05-2.3 μM for pig and rat liver OSC) and fungal cell-free Candida albicans OSC (submicromolar IC₅₀ values). In particular, the S-18 analogue 3 showed the most potent inhibition toward the rat liver enzyme (IC₅₀ = 50 nM) and showed potent, selective inhibition against the fungal enzyme (IC₅₀ = 0.22 nM, 10-fold more potent than the S- 19 analogue 4). Thus, 3 is the most potent OSC inhibitor known to date. The K(i) values ranged from 0.5 to 4.5 μM for pig OSC, with 3 and 4 showing about 10-fold higher potency for rat liver OSC. Interestingly, the S-18 analogue 3 showed time-dependent irreversible inhibition with homogeneous pig liver OSC (k(inact) = 0.06 min^-1) but not with rat OSC.

Full text of DOI:10.1021/jm960483a

J . Med. Chem. 1997, 40, 201-209
201
Syn th esis a n d In h ibition Stu d ies of Su lfu r -Su bstitu ted Squ a len e Oxid e
An a logu es a s Mech a n ism -Ba sed In h ibitor s of 2,3-Oxid osqu a len e-La n oster ol
Cycla se†
Dirk Stach,‡ Yi Feng Zheng,*,@ Alice L. Perez,§ and Allan C. Oehlschlager*
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
Ikuro Abe*,@ and Glenn D. Prestwich*,@
Department of Chemistry, University at Stony Brook, Stony Brook, New York 11794-3400
Peter G. Hartman
F. Hoffmann-La Roche Ltd., CH-4002 Basel, Switzerland
Received J uly 5, 1996X
The synthesis and biological evaluation of three new sulfur-substituted oxidosqualene (OS)
analogues (1-3) are presented. In these analogues, C-11, C-15, or C-18 in the OS skeleton
was replaced by sulfur. The sulfur position in the OS skeleton was chosen to disrupt one or
more key processes involved in cyclization: (a) the folding of the B-ring into a boat conformation,
(b) the anti-Markovnikov cyclization leading to the C-ring, or (c) the formation of the D-ring
during the lanosterol biosynthesis. Enzyme inhibition kinetics using homogeneous mammalian
oxidosqualene cyclases (OSC) were also examined for the previously reported S-19 analogue 4.
The four analogues were potent inhibitors of mammalian OSCs (IC50 ) 0.05-2.3 µM for pig
and rat liver OSC) and fungal cell-free Candida albicans OSC (submicromolar IC50 values).
In particular, the S-18 analogue 3 showed the most potent inhibition toward the rat liver enzyme
(IC50 ) 50 nM) and showed potent, selective inhibition against the fungal enzyme (IC50 ) 0.22
nM, 10-fold more potent than the S-19 analogue 4). Thus, 3 is the most potent OSC inhibitor
known to date. The Ki values ranged from 0.5 to 4.5 µM for pig OSC, with 3 and 4 showing
about 10-fold higher potency for rat liver OSC. Interestingly, the S-18 analogue 3 showed
time-dependent irreversible inhibition with homogeneous pig liver OSC (kinact ) 0.06 min-1
but not with rat OSC.
)
In tr od u ction
in aromatic amino acids (six repeats in both OSCs and
SCs).5 The â-strand turn motif was well-conserved, and
it has been postulated that the aromatic amino acids of
the QW motif might play a structural or functional role
in catalysis by stabilizing the carbocationic intermedi-
ates through cation-π-interactions.4d,e
Cyclization of 2,3-oxidosqualene (OS) to lanosterol
mediated by 2,3-oxidosqualene-lanosterol cyclase (OSC)
involves formation of the protosterol cation and its
backbone rearrangement to lanosterol and proceeds via
distinct carbocationic intermediates (Scheme 1).1,2
J ohnson and co-workers3 hypothesized that a stereo-
controlled delivery of “point-charge” nucleophiles by the
enzyme could stabilize each cationic intermediate. The
cyclization process has been the subject of numerous
biomimetic studies.1
Lanosterol synthases have been cloned and sequenced
from several sources.4 Rat liver OSC, an 83-kDa
membrane-associated protein, has been cloned and
functionally expressed.4e The deduced amino acid se-
quence of the rat enzyme showed significant homology
to the known OSCs from yeast and plant (39-44%
identity) and still retained 17-26% identity with bacte-
rial squalene cyclases (SCs). Sequence comparisons of
eukaryotic OSCs and bacterial SCs have revealed the
presence of the QW motif, a highly-conserved motif rich
For several decades, OSCs have been the targets of
inhibition studies.6 Inhibition of OSCs has been achieved
by substrate analogues7 as well as mimics of the
presumed carbocationic intermediates.8 Recently, at-
tention has focused on the design of mechanism-based
inactivators.1,9 Ceruti et al.10 examined squalenoid
epoxide vinyl ethers as possible “suicide” inhibitors. The
authors suggested that cyclization of such substrates
would form a C-20 carbocation, which could be stabilized
through formation of an oxocarbenium ion. The latter
could interact with an active site nucleophile producing
irreversible enzyme inhibition. In fact, the vinyl ether-
containing squalene oxides were competitive inhibitors,
i.e., 22,23-dihydro-20-oxa-2,3-oxidosqualene showed a Ki
of 60 µM and an IC50 of 80 µM for rat liver OSC. A
potent irreversible inactivator of pig liver OSC, 29-
methylidene-2,3-oxidosqualene (29-MOS),11 exhibited an
IC50 value of 0.5 µM and a kinact of 221 min-1. The
reactive intermediate partitioned to give a product, 21-
methylidenelanosterol, that could be isolated in low
yield as a cyclization product of 29-MOS.11c Both
inhibition and cyclization appear to occur via a common
† Dedicated to the memory of Professor William S. J ohnson, friend
and mentor.
@ Address correspondence to these authors at: Department of
Medicinal Chemistry, The University of Utah, Salt Lake City, Utah
84112.
‡ Permanent address: Brillux, Weseler Straâe 401, 48163 Mu¨nster,
Germany.
§ Department of Chemistry, University of Costa Rica, 2060 San
Pedro, San J ose´, Costa Rica.
X Abstract published in Advance ACS Abstracts, J anuary 1, 1997.
S0022-2623(96)00483-9 CCC: $14.00 © 1997 American Chemical Society

202 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2
Stach et al.
Sch em e 1. Proposed Cyclization Mechanism of Oxidosqualene into Lanosterol
cationic intermediate.11,12 An Asp residue (D456 in rat
OSC) in a highly-conserved sequence (DCTAE motif)
was covalently modified by [3H]-29-MOS.4e,12 Corey et
al.13 found 10,15-didesmethyl-OS to be a time-dependent
irreversible inhibitor of yeast cyclase, but the covalent
modification of protein was not confirmed. Abad et al.14
found that 2,3:18,19-dioxidosqualene was a potent
noncompetitive inhibitor (IC50 ) 0.11 µM) of rat liver
OSC.
Introduction of sulfur (Scheme 3) was achieved through
reaction of homofarnesol8a (12) with thiolacetic acid via
a modified Mitsunobu reaction18 to give the thioacetate
13. The resulting thioacetate was reduced to the
desired thiol 14 with LiAlH4 (85% yield). Coupling of
thiol 14 and mesylate 11 was carried out using 50%
NaOH in aqueous toluene in the presence of tetraocty-
lammonium bromide as a phase transfer catalyst,19
giving product 1 in 29% yield.
More recently, Zheng et al. described a series of sulfur
and sulfoxide OS analogues in which sulfur has replaced
carbon C-5, C-6, C-8, C-9, C-10, C-13, C-14, C-16, C-19,
or C-20; many are good inhibitors of OSC.15,16 Among
them, the S-19 analogue 4 resulted in extremely potent
inhibition (IC50 ) 0.0023 µM) of Candida albicans
OSC.15b Here we now report the synthesis and biologi-
cal activity of a new set of thia-OS analogues (1-3), in
which C-11, C-15, or C-18 in the OS skeleton was
replaced by sulfur (Figure 1). The sulfur position in the
OS skeleton was chosen to interfere with (a) the folding
of the B-ring into a boat conformation, (b) the anti-
Markovnikov cyclization leading to the C-ring, and (c)
the formation of the D-ring during the lanosterol bio-
synthesis. We propose that inhibition could occur via
interruption of the cyclization process, trapping the
generated carbocations as sulfonium intermediates. Our
strategy employs the sulfur atom as a π-donor that
mimics a double bond. Enzyme inhibition kinetics using
homogeneous mammalian OSC are also presented for
the S-19 analogue 4, and implications for the enzyme
inhibition mechanism are discussed.
The low yield of the coupling reaction can be at-
tributed to low reactivity of the secondary mesylate 11
toward the thiol anion. Attempts to improve the yield
of the coupling by use of the triflate of 10 failed.
Although the triflate could be formed, coupling condi-
tions led primarily to alcohol 10 with <5% coupling. The
1
structure of 1 was confirmed by appearance in the H
NMR spectrum of signals attributable to the protons R
to the sulfur, δ 2.75 (m, CH3CHS) and 2.50 (t, J ) 8
Hz, CH2S), as well as a signal at δ 2.70 (t, J ) 6.5 Hz)
confirming the presence of the epoxide.
A similar strategy was applied to the synthesis of 2.
As shown in Scheme 2, 4,8,12-trimethyl-(3E,7E),11-
tridecatrien-1-ol (15)20 was protected as the tert-bu-
tyldimethylsilyl ether in CH2Cl2 and then converted to
the terminal bromohydrin 17. Reaction of 17 with 2.5%
K2CO3 in methanol afforded 18 (35% yield for three
steps). Deprotection of 18 was achieved with Bu4NF
in THF to give epoxy alcohol 19 in 94% yield. Subse-
quent mesylation gave 20, which was used without
further purification.
Homogeraniol (21) (Scheme 3) was prepared in good
yield by the method of Leopold.21 Reaction of homoge-
raniol (21) with thiolacetic acid followed by reduction
with LiAlH4 gave thiol 23 in good yield. Coupling of
crude mesylate 20 with thiol 23 was carried out as
described above for the synthesis of 1. Thus, thiol 23
was treated with 50% aqueous NaOH in toluene, tet-
raoctylammonium bromide, and mesylate 20. After 15
h at 40 °C the desired compound 2 was isolated in 65%
Resu lts a n d Discu ssion
Syn th esis of 2,3-OS An a logu es. The candidate
inhibitors 1-3 were prepared through coupling of a
suitable alkylthiolate anion and an electrophile as
described previously.15a Thus, for the synthesis of 1,
geranylacetone (5) (Scheme 2) was reduced, protected
as a tert-butyldimethylsilyl ether, and then converted
with N-bromosuccinimide in THF-H2O (4:1)17 into the
corresponding terminal bromohydrin 8 (39% yield for
two steps). The latter was transformed to epoxide 9
using K2CO3/MeOH (96% yield) and deprotected using
tetrabutylammonium fluoride to give the epoxy alcohol
10 (98% yield), which was converted into the corre-
sponding mesylate 11. After workup, 11 was used for
further reaction without purification.
1
yield. A signal in the H NMR spectrum of 2 at δ 2.50
(m, 4H, 2 × S-CH2) indicated successful coupling, while
a signal at δ 2.70 (t, J ) 6 Hz) confirmed the presence
of the epoxide structure.
Preparation of 3, in which sulfur replaces the nucleo-
philic carbon at position 18 of the 2,3-OS skeleton, is
also outlined in Schemes 2 and 3. Reaction of 249a with
NBS in THF-H2O gave the terminal bromohydrin 25,

Sulfur-Containing Inhibitors of Lanosterol Synthase
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2 203
Sch em e 2a
a
Reagents: (a) LAH, THF; (b) TBSCl, DMAP, Et3N, CH2Cl2; (c) NBS, THF, H2O, 0 °C; (d) 2.5% K2CO3, MeOH; (e) Bu4NF, THF, H2O;
(f) CH3SO2Cl, DMAP, Et3N, CH2Cl2.
analogue 4) in the series of sulfur-containing analogues
prepared so far.15,16 This was the best OSC inhibition
known so far. For rat OSC, compound 3 is in fact far
more potent than inhibitors such as 29-MOS (IC50 ) 0.3
µM)11 and 2,3:18,19-dioxidosqualene (IC50 ) 0.11 µM).14
Interestingly, compounds 3 and 4 showed extremely low
IC50 values (0.000 22 and 0.0023 µM, respectively)
toward the fungal OSC compared with those for mam-
malian OSCs (2.3 and 1.0 µM, respectively, for pig OSC),
suggesting striking species selectivity of the inhibition
activities between fungal and mammalian OSCs.15b The
1000-fold selectivity between fungal and pig OSC ob-
served for compound 3 has never been achieved before.23
Compounds 3 and 4 thus have potential for development
as potential antifungal agents. These observations
support the idea that small changes in the amino acid
sequence substantially affect the susceptibility of these
F igu r e 1. Sulfur-substituted 2,3-oxidosqualene analogues.
enzymes to inhibitors. The deduced amino acid se-
quence of C. albicans OSC showed ca. 40% identity with
that of rat OSC.8e Furthermore, as mentioned above,
which was converted to the terminal epoxide 26 by K2-
CO3/MeOH in 37% yield for two steps. Removal of the
silyl protecting group of 26 followed by mesylation
provided 28. The required thiol 31 was prepared from
in the entire series of sulfur-containing OS analogues,
compounds 3 (S-18) and 4 (S-19) showed the most potent
alcohol 29 in 76% yield for two steps. Synthesis of 3
inhibition, which supports the suggestion by Zheng et
was completed by coupling 28 and 31 in 74% yield. 1H
al.15a that modifications of the prering D region of OS
NMR spectral analysis confirmed the structure of 3. The
should yield potent inhibition.
sulfur-containing OS analogue 4 (sulfur replaces C-19
in OS) was available from previous work.15a
Kinetic analyses revealed that 1-4 are competitive
inhibitors of pig liver OSC22 with Ki values of 0.5, 4.5,
1.5, and 1.4 µM, respectively (Table 1). For rat liver
OSC, 3 and 4 showed potent inhibition with Ki values
of 0.037 and 0.18 µM, respectively. Further, for both
enzymes, the time dependency of inactivation was
measured, and the rates of inactivation (kinact) were
calculated (Table 1).
Biologica l Resu lts. Compounds 1-4 (all prepared
in racemic form) were quite potent inhibitors of cell-
free C. albicans and homogeneous rat and pig liver
OSCs22 (Table 1). In particular, the S-18 analogue 3
showed the most potent inhibition toward rat liver (IC50
) 0.050 µM) and C. albicans OSC (IC50 ) 0.000 22 µM,
10-fold more potent than the previously reported S-19

204 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2
Stach et al.
Sch em e 3a
a
Reagents: (a) PPh3, DIAD, CH3COSH, THF; (b) LAH, Et2O; (c) 50% NaOH, Oct4NBr, PhCH3, H2O, 40 °C.
Ta ble 1
Interestingly, for rat liver OSC, both compounds 3 and
4 showed inhibition that was independent of preincu-
bation time (Table 1). Furthermore, we have recently
found that inhibition of pig OSC by 3 was irreversible
and that tritium-labeled S-18 analogue 3 covalently
modified the enzyme.15c Rat OSC was not covalently
modified by radiolabeled 3, confirming the species
selectivity observed in the kinetic behavior.
In inhibitors 1-4, sulfur atoms were positioned to
interfere with cyclization leading to rings B, C, and D.
It is possible that 1-4 could bind to OSCs and could be
cyclized to 32-35, respectively (Figure 3). Inhibition
could result from partially-cyclized intermediates such
as these or from a conformational change of the sub-
strate, a conformational change in the enzyme, or a
reaction of the substrate mimic with OSC.25 In any
case, it seems reasonable that bicyclic, tricyclic, or
tetracyclic sulfonium ions, if formed, could be stabilized
by nucleophilic residues at the active sites of the
cyclases.
As described above, the S-18 analogue 3 is an ex-
tremely potent, time-dependent, and irreversible inhibi-
tor of pig OSC. If it is assumed that 3 is cyclized to a
tricyclic sulfonium ion (34), reaction with the OSC could
then occur in several ways:26 (i) nucleophilic attack at
the R-carbon to give a thioether with alkylation of OSC,
(ii) â-elimination by a basic residue to give the thioether
and an alkene, or (iii) proton abstraction R to the
sulfonium to form an ylide, with possible subsequent
compd
IC50 (µM)
Rat Liver (Purified)15b
0.050
0.26
0.3
Ki (µM)
kinact (min-1
)
3
4
0.037
0.18
2.5
0.0001
0.0001
NDa
29-MOS
Pig Liver (Purified)
1
2
3
4
0.7
2.3
2.3
1.0
0.5
0.5
4.5
1.5
1.4
4.4
0.04
0.13
0.06
0.0001
221
29-MOS
C. albicans (Cell-free)
0.54
8.4
1
2
3
4
0.00022
0.002315a
a
ND, not determined.
The time dependency of inactivation of pig liver OSC
by compounds 3 and 4 is shown in Figure 2. The S-18
analogue 3 showed a significant ability to decrease the
activity of pig liver OSC. Its ability to inactivate the
enzyme was comparable to that of 29-MOS,11 although
its time course was 3 orders of magnitude slower. In
contrast, inhibition by the S-19 analogue 4 did not show
time dependency. Small changes in the location of
sulfur (C-19 or C-18), therefore, can significantly affect
the inhibitory activity. Indeed, 3 acted as a time-
dependent, mechanism-based inhibitor for pig liver
OSC, while 4 acted only as a competitive inhibitor.

Sulfur-Containing Inhibitors of Lanosterol Synthase
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2 205
modified amino acid, the pendant partially-cyclized
derivative of 3, and the partitioning to released cycliza-
tion products of 3 are currently under investigation.
Exp er im en ta l Section
Gen er a l Ch em ica l P r oced u r es. Nuclear magnetic reso-
nance (NMR) spectroscopy was conducted on a Bruker AMX-
400 spectrometer at 400.13 and 100.62 MHz for 1H and 13C
NMR spectra, respectively. All spectra were run in deuterio-
chloroform. 1H NMR chemical shifts are reported in parts per
million (ppm, δ) relative to TMS (0.00 ppm). 13C NMR spectra
are referenced to CDCl3 (77.0 ppm). Mass spectra were
obtained using a Hewlett-Packard 5985B GC-MS instrument
equipped with a DB-1 coated column (30 m × 0.32 mm i.d.,
0.25 µm film) operating at 70 eV for electron impact (EI)
ionization. Chemical ionization (CI) was performed using
isobutane as a proton source, and data are quoted in relative
intensity. IR spectra were recorded on a Perkin-Elmer Model
FT 1605 spectrophotometer. Elemental analyses were ob-
tained using a Carbo Erba Model-1106 elemental analyzer.
Tetrahydrofuran (THF) and diethyl ether (Et2O) were freshly
distilled from sodium benzophenone-ketyl. Diisopropylamine
and triethylamine were distilled from CaH2 and stored under
a nitrogen atmosphere. CH2Cl2 was distilled from CaH2 prior
to use. N-Bromosuccinimide was recrystallized from water
and dried under high vacuum. Chemicals obtained from
commercial sources were used without further purification. All
moisture- and air-sensitive reactions were conducted under a
positive pressure of argon in glassware that was flame-dried
under vacuum. A nitrogen glovebag was used to weigh all the
moisture- and oxygen-sensitive compounds. Syringes and
cannulas were used to transfer oxygen- and water-sensitive
liquid reagents. Standard workup refers to the combining of
organic extracts, washing with ice-cold brine, and drying over
MgSO4. This is followed by filtration and solvent removal
under reduced pressure. Chromatography refers to flash
chromatography using Merck silica gel 60, mesh 230-400.
Biologica l P r oced u r es. 1. En zym e In h ibition Assa y
(C. a lbica n s). The assay procedure is that reported by Zheng
et al.15a
2. En zym e In h ibition Assa y a n d Kin etics Deter m in a -
tion s (P ig liver OSC). Inhibitors were preincubated for 10
min at 37 °C in a mixture of phosphate buffer, pH 7.40, and
[14C]-(3S)-2,3-oxidosqualene27 before addition of the enzyme
solution (specific activity ) 2643 nmol of lanosterol formation/
h/mg)22 and then incubated for 1 h. The reaction was stopped
by addition of 0.1% lanosterol solution. The sample was then
spotted (2 × 50 µL) on TLC plates (Whatman silica gel 60 Å
with preabsorbant strip), developed with CH2Cl2, and analyzed
by radio-TLC scanning using an imaging scanner (BioScan
System 500). The Ki values were determined using the same
conditions as above. Substrate concentration was adjusted to
final concentrations of 20, 25, 33, and 50 µM. Inhibitor
concentrations were adjusted to (1) 0.0, 0.5, and 1.0 µM; (2)
0.0, 1.5, and 2.5 µM; (3) 0.0, 1.0, and 2.0 µM; and (4) 0.0, 0.5,
and 1.0 µM. The Ki calculation was done using the BMDP
Statistical Software for derivative-free nonlinear regression.24
3. Tim e Dep en d en cy. The assays were conducted at 37
°C in glass microtubes. The tubes containing 60 µL of 0.1%
Triton X-100 in 0.1 M phosphate buffer, pH 7.40, 39 µL of
phosphate buffer, pH 7.40, and 1 µL of [14C]-(3S)-2,3-oxi-
dosqualene were preincubated for 10 min. A preincubated 20-
µL aliquot from a mixture of 119 µL of homogeneous pig liver
OSC and 1 µL of each inhibitor (1, 0.0, 0.5, 1.0, and 1.5 µM; 2,
0.0, 0.6, 1.2, and 2.4 µM; 3, 0.0, 1.0, 2.0, and 3.0 mM; 4, 0.0,
0.5, 0.75, and 1.0 µM) was added at 0, 3, 5, and 7 min for
inhibitors 1 and 2 and at 0, 4, 7.5, and 10.5 min for inhibitors
3 and 4. The samples were incubated for 1 h prior to TLC
analyses.
F igu r e 2. Time-dependent inactivation of pig liver OSC by
compounds 3 and 4.
F igu r e 3. Putative sulfonium ions resulting from participa-
tion of S-11, S-15, S-18, or S-19 in cyclization of analogues 1-4.
alkylation. Recently, we have prepared both [17-3H]-
and [22-3H]-3 and found that both of the labeled
regioisotopomers covalently modified the enzyme.15c The
retention of the tritium label for both isotopomers
excluded the possibility of an attack at C-20 with
transfer of the side chain to the active site. Nucleophilic
trapping could alternatively occur on a bicyclic or
tricyclic intermediate.15c Elucidation of the covalently-
6,10-Dim eth yl-(5E),9-u n d eca d ien -2-ol (6). To a slurry
of LiAlH4 (1.0 g, 26.0 mmol) in 30 mL of THF, under an
atmosphere of argon, was added dropwise a solution of ketone
5 (5.0 g, 26.0 mmol) in 15 mL of THF. The reaction was
refluxed for 30 min, at which time excess LiAlH4 was destroyed
at 0 °C by slow addition of 1.0 mL of water followed by 1.0 mL

206 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2
Stach et al.
of 15% NaOH followed by 3.0 mL of water. The resulting
solids were filtered and rinsed thoroughly with small portions
of Et2O (5 × 20 mL). Standard workup followed by chroma-
tography using ethyl acetate/hexanes (2/1) as an eluant
afforded 6 (4.8 g, 94%) as an oil. IR (neat): 3342 (b), 2922,
Hz, 3H); 13C NMR: δ 134.1, 124.6, 67.2, 63.9, 58.0, 39.0, 36.1,
27.2, 24.6, 24.1, 23.2, 18.4, 15.6. CIMS: m/ z 212 (M+, 0.4),
194 (1), 153 (4), 123 (10), 121 (11), 112 (12), 85 (100), 81 (79),
77 (17), 72 (30), 71 (62), 69 (56), 68 (19), 67 (78), 59 (64). Anal.
(C13H24O2) C,H.
6,10-Dim eth yl-9,10-ep oxy-(5E)-u n d ecen -2-yl Meth a n e-
su lfon a te (11). To a solution of epoxy alcohol 10 (0.20 g, 0.94
mmol) in CH2Cl2 (30 mL) at -50 °C were added triethylamine
(0.15 g, 1.48 mmol) and methanesulfonyl chloride (0.14 g, 1.22
mmol). The mixture was stirred at -50 °C for 5 min and then
warmed to 0 °C. The reaction mixture was poured into water,
the organic layers were separated, and the aqueous layer was
extracted with ether (3 × 30 mL). After the combined extracts
were dried over MgSO4, the solvents were removed in vacuo
and the resulting product 11 was used in the next reaction
without further purification.
2895, 2884, 1449, 1384, 1119, 1061, 826, 737 cm-1 1H NMR:
.
δ 5.10 (m, 2H), 3.80 (m, 1H), 2.07 (m, 4H), 1.98 (m, 2H), 1.67
(s, 3H), 1.62 (s, 3H), 1.59 (s, 3H), 1.49 (m, 2H), 1.18 (d, J ) 6
Hz, 3H). 13C NMR: δ 135.4, 131.1, 124.2, 123.9, 67.6, 39.62,
39.1, 26.5, 25.5, 24.2, 23.2, 17.5, 15.8. CIMS: m/ z 196 (M+,
1), 178 (0.5), 163 (3), 153 (37), 135 (25), 123 (11), 109 (75), 107
(11), 95 (19), 93 (11), 81 (32), 69 (100), 67 (82), 55 (19). Anal.
(C13H24O) H; C: calcd, 79.52; found, 79.10.
1,5,9-Tr im eth yl-(4E),9-d eca d ien yl ter t-Bu tyld im eth yl-
silyl Eth er (7). To a solution of 6 (4.0 g, 20.4 mmol) in 50
mL of CH2Cl2 were added Et3N (2.91 g, 30.6 mmol), tert-
butyldimethylsilyl chloride (3.67 g, 24.3 mmol), and 4-(dim-
ethylamino)pyridine (0.05 g, 0.4 mmol) as a catalyst. The
mixture was stirred overnight at room temperature. Standard
workup followed by chromatography using ethyl acetate/
hexanes (1/2) as eluant afforded the protected alcohol 7 (6.0
g, 95%) as an oil. IR (neat): 2960, 2882, 2860, 1454, 1372,
4,8,12-Tr im eth yl-(3E,7E),11-tr id eca tr ien yl Th ioa ceta te
(13). To a stirred solution of triphenylphosphine (7 g, 26.7
mmol) in THF (70 mL) was added diisopropyl azodicarboxylate
(5.6 g, 26.7 mmol) at 0 °C. The mixture was stirred for 0.5 h,
after which time a mixture of thioacetic acid (2.0 g, 26.6 mmol)
and homofarnesol (12)8a (3.1 g, 13.3 mmol) in THF (30 mL)
was added, while the temperature was maintained below 0
°C. The reaction mixture was stirred for 1.5 h at 0 °C and
overnight at room temperature. After standard workup,
chromatography using ethyl acetate/hexanes (1/20) as eluant
afforded 13 (3.28 g, 80%) as a yellow liquid. IR (neat): 2965,
1249, 1137, 1090, 1037, 831, 767 cm-1 1H NMR: δ 5.10 (m,
.
2H), 3.78 (m, 1H), 2.05 (m, 2H), 1.96 (m, 2H), 1.67 (s, 3H),
1.59 (s, 3H), 1.58 (s, 3H), 1.55 (s, 3H), 1.11 (d, J ) 6 Hz, 3H),
0.89 (s, 9H), 0.06 (s, 6H). 13C NMR: δ 135.0, 124.5, 124.4,
68.4, 39.9, 39.8, 26.8, 25.9, 25.6, 24.3, 23.7, 18.2, 17.6, 16.0,
-4.4, -4.7. CIMS: m/ z 310 (M+, 1), 253 (20), 177 (15), 143
(2), 135 (10), 109 (70), 75 (100), 59 (10). Anal. (C19H38OSi)
C,H.
2925, 2854, 1694, 1442, 1381, 1352, 1134, 1107, 950, 835 cm-1
.
1H NMR: δ 5.10 (m, 3H), 2.82 (t, J ) 8 Hz, 2H), 2.30 (s, 3H),
2.21 (m, 2H), 2.05-1.96 (m, 8H), 1.69 (s, 3H), 1.62 (s, 3H), 1.59
(s, 6H). 13C NMR: δ 195.7, 137.5, 135.0, 131.1, 124.3, 123.9,
121.7, 39.6, 39.5, 30.5, 29.4, 27.9, 26.7, 26.4, 25.6, 23.2, 17.6,
16.1, 15.5. CIMS: m/ z 294 (M+, 2), 251 (9), 218 (2), 183 (5),
175 (3), 115 (17), 81 (52), 69 (100). Anal. (C18H30OS) C,H.
4,8,12-Tr im eth yl-(3E,7E),11-tr id eca tr ien e-1-th iol (14).
To a solution of LiAlH4 (0.61 g, 16 mmol) in THF (20 mL) was
added dropwise a solution of 13 (0.62 g, 2 mmol) in THF (10
mL) at 0 °C. After 0.5 h excess LiAlH4 was destroyed at 0 °C
by slow addition of 1.0 mL of water followed by 1.0 mL of 15%
NaOH followed by 3.0 mL of water. The resulting solids were
filtered and rinsed thoroughly with small portions of Et2O (5
× 20 mL). Standard workup followed by chromatography
using hexanes as an eluant afforded 14 (0.43 g, 85%) as a
yellow liquid. IR (neat): 2920, 2560, 1736, 1670, 1450, 1275,
10-[(ter t-Bu tyldim eth ylsilyl)oxy]-3-br om o-2,6-dim eth yl-
(6E)-u n d ecen -2-ol (8). A solution of the protected alcohol 7
(6.0 g, 19.3 mmol) in THF (370 mL) and water (100 mL) was
treated with N-bromosuccinimide (3.44 g, 19.3 mmol) in THF
(60 mL) and water (20 mL), while the temperature was kept
at 0 °C. After the reaction mixture was stirred for 1 h at 0
°C, THF was removed in vacuo. Standard workup followed
by column chromatography using ethyl acetate/hexanes (20/
1) as the eluant afforded the bromohydrin 8 (5.9 g, 76%, two
cycles) as a colorless oil. IR (neat): 3451 (b), 2956, 2856, 1471,
1373, 1254, 1134, 1090, 1035, 906, 835, 774 cm-1
.
1H NMR:
δ 5.20 (t, J ) 6 Hz, 1H), 3.96 (m, 1H), 3.75 (m, 1H), 1.90-2.35
(m, 8H), 1.59 (s, 3H), 1.55 (s, 6H), 1.33 (d, J ) 7 Hz, 3H), 0.89
(s, 9H), 0.05 (s, 6H). 13C NMR: δ 133.1, 126.1, 72.4, 70.7, 68.3,
39.7, 38.2, 32.2, 26.6, 25.9, 24.3, 23.7, 23.7, 18.1, 15.8, -4.4,
-4.7. CIMS: m/ z 409/407 (M+ + 1, 12/12), 391 (3), 327 (5),
277 (65), 276 (15), 275 (54), 274 (8), 259 (16), 257 (18), 195
(46), 177 (100). Anal. (C19H39BrO2Si) C,H.
1100, 970, 835 cm-1 1H NMR: δ 5.10 (m, 3H), 2.83 (t, J ) 8
.
Hz, 2H), 2.23 (m, 2H), 2.10-1.95 (m, 8H), 1.66 (s, 3H), 1.61
(s, 3H), 1.59 (s, 6H). 13C NMR: δ 137.5, 134.9, 131.0, 124.4,
123.9, 121.8, 39.7, 39.6, 31.9, 30.5, 29.4, 28.0, 26.7, 26.4, 25.6,
17.6, 16.1, 15.9. CIMS: m/ z 252 (M+, 15), 237 (20), 209 (70),
169 (55), 136 (74), 115 (37), 81 (90), 69 (100). HRMS Calcd
for C16H28Si: 252.1912. Found: 252.1867.
2-[(ter t-Bu tyld im eth ylsilyl)oxy]-6,10-d im eth yl-9,10-ep -
oxy-(5E)-u n d ecen e (9). To a solution of powdered K2CO3 (3.6
g, 26.0 mmol) in 50 mL of methanol was added the bromohy-
drin 8 (5.3 g, 13.0 mmol), and the reaction mixture was stirred
for 1 h at room temperature. Methanol was removed in vacuo;
the resulting slurry was diluted with water (50 mL) and
extracted with ether (3 × 50 mL). Standard workup and
chromatography using ethyl acetate/hexanes (1/5) as an eluant
afforded 9 (4.1 g, 96%) as an oil. IR (neat): 2958, 2856, 1461,
6,10-Dim eth yl-9,10-ep oxy-(5E)-u n d ecen yl 4′,8′,12′-Tr i-
m eth yl-(3E,7E),11-tr id eca tr ien yl Su lfid e (1). To a solution
of NaOH (5 g, 0.12 mol) in H2O (10 mL) and toluene (10 mL)
were added tetraoctylammonium bromide (0.05 g, 0.1 mmol),
thiol 14 (0.25 g, 1 mmol), and mesylate 11 (0.29 g, 1 mmol) at
room temperature. The mixture was then warmed to 40 °C
and stirred overnight. Standard workup followed by chroma-
tography using ethyl acetate/hexanes (1/20) as the eluant
yielded 1 (0.13 g, 29%). IR (neat): 2960, 2923, 2855, 1449,
1376, 1253, 1134, 1087, 1039, 835, 774 cm-1 1H NMR: δ 5.15
.
(t, J ) 6 Hz, 1H), 3.76 (m, 1H), 2.70 (t, J ) 6 Hz, 1H), 1.90-
2.21 (m, 8H), 1.57 (s, 3H), 1.29 (s, 3H), 1.22 (3H), 1.12 (d, J )
7 Hz, 3H), 0.88 (s, 9H), 0.05 (s, 6H). 13C NMR: δ 134.1, 125.0,
68.3, 58.2, 39.8, 36.3, 27.5, 25.9, 25.7, 24.8, 24.2, 23.7, 18.7,
18.1, 15.9, -4.3, -4.6. CIMS: m/ z 327 (M+ + 1, 26), 309 (16),
269 (8), 196 (13), 195 (100), 178 (11), 177 (79), 153 (8). Anal.
(C13H38O2Si) C,H.
1376, 1248, 1121, 835 cm-1
.
1H NMR: δ 5.12 (m, 4H), 2.75
(m, 1H), 2.69 (t, J ) 6.5 Hz, 1H), 2.50 (t, J ) 8 Hz, 2H), 2.25
(m, 2H), 2.18-1.94 (m, 20H), 1.77 (s, 3H), 1.65 (s, 3H), 1.62
(s, 3H), 1.59 (s, 6H), 1.57 (s, 3H), 1.29 (s, 3H), 1.27 (d, J ) 8.5
Hz, 3H), 1.25 (s, 3H). 13C NMR: δ 136.6, 135.0, 134.7, 131.2,
124.5, 124.1, 123.5, 122.7, 64.1, 58.2, 39.9, 39.7, 37.1, 36.4, 33.9,
32.0, 30.6, 28.7, 27.5, 26.6, 25.6, 25.5, 24.9, 23.4, 22.6, 18.7,
17.7, 16.7, 16.2. CIMS: m/ z 447 (M+ + 1, 55), 269 (23), 253
(100), 227 (71), 211 (46), 195 (38), 177 (31), 137 (35). HRMS
Calcd for C29H50OS: 446.3582. Found: 446.3588.
6,10-Dim eth yl-9,10-ep oxy-(5E)-u n d ecen -2-ol (10). Silyl
ether 9 (4.1 g, 12.5 mmol) was dissolved in 30 mL of a 1.0 M
solution of tetrabutylammonium fluoride in THF, and the
solution was stirred for 4 h at room temperature. The solution
was diluted with water (100 mL) and extracted with ether (4
× 40 mL). Standard workup followed by chromatography
using ethyl acetate/hexanes (1/1) as the eluant yielded 10 (2.6
g, 98%) as a colorless oil. IR (neat): 3427 (b), 2963, 2925, 1741,
1-[(t er t -B u t y ld im e t h y ls ily l)o x y ]-5,9,13-t r im e t h y l-
(4E,8E),12-tetr a d eca tr ien e (16). To a solution of alcohol 15
(4.0 g, 16.0 mmol) in 50 mL of CH2Cl2 was added Et3N (2.5 g,
24.7 mmol), tert-butyldimethylsilyl chloride (3.0 g, 20.0 mmol),
and 4-(dimethylamino)pyridine (0.1 g, 0.8 mmol). The mixture
was stirred overnight at room temperature. Standard workup
1451, 1378, 1248, 1124, 953, 868 cm-1 1H NMR: δ 5.18 (t, J
.
) 6 Hz, 1H), 3.80 (m, 1H), 2.69 (t, J ) 6 Hz, 1H), 2.02 -2.20
(m, 8H), 1.62 (s, 3H), 1.30 (s, 3H), 1.25 (s, 3H), 1.19 (d, J ) 7

Sulfur-Containing Inhibitors of Lanosterol Synthase
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2 207
followed by chromatography using ethyl acetate/hexanes (1/
15) as eluant afforded the protected alcohol 16 (5.06 g, 87%)
as an oil. IR (neat): 2928, 2851, 1444, 1383, 1255, 1099, 836,
overnight at room temperature. Standard workup with SiO2
chromatography using ethyl acetate/hexanes (1/20) as eluant
afforded 22 (0.54 g, 80%). IR (neat): 3350, 2910, 1690, 1435,
775 cm-1
.
1H NMR: δ 5.12 (m, 3H), 3.60 (t, J ) 6.0 Hz, 2H),
1350, 1130, 1100, 950, 830, 735 cm-1 1H NMR: δ 5.10 (m,
.
2.10-1.95 (m, 10H), 1.68 (s, 3H), 1.60 (s, 9H), 1.55 (m, 2H),
0.90 (s, 9H), 0.05 (s, 6H). 13C NMR: δ 135.3, 134.9, 124.5,
124.3, 124.1, 62.7, 39.7, 33.1, 26.8, 26.7, 26.0, 24.6, 24.2, 18.3,
17.6, 16.0, -5.3. CIMS: m/ z 365 (M+ + 1), 307 (6), 234 (18),
233 (100), 231 (24). Anal. (C23H44OSi) C,H.
2H), 2.85 (t, J ) 7 Hz, 2H), 2.31 (s, 3H), 2.25 (m, 2H), 2.06-
1.95 (m, 4H), 1.67 (s, 3H), 1.60 (s, 3H), 1.59 (s, 3H). The 1H
NMR spectrum was in agreement with that reported in ref
28.
4,8-Dim eth yl-(3E),7-n on a d ien eth iol (23). To a stirred
solution of 2.5% KOH in methanol (10 mL) was added thiol
22 (0.5 g, 1.9 mmol) at room temperature. The mixture was
stirred for 4 h, after which time most of the methanol was
removed in vacuo. The resulting slurry was diluted with water
(20 mL) and extracted with Et2O (3 × 20 mL). Standard
workup and chromatography using hexanes as the eluant
afforded 23 (0.31 g, 88%) as a yellow liquid. 1H NMR: δ 5.10
(m, 2H), 2.51 (dt, J ) 7.0, 7.5 Hz, 2H), 2.30 (m, 2H), 2.05 (m,
2H), 2.00 (m, 2H), 1.67 (s, 3H), 1.61 (s, 3H), 1.59 (s, 3H), 1.41
3-Br om o-2,6,10-tr im eth yl-14-[(ter t-bu tyld im eth ylsilyl)-
oxy]-(6E,10E)-tetr a d eca d ien -2-ol (17). A solution of the
protected alcohol 16 (5.0 g, 13.7 mmol) in THF (370 mL) and
water (100 mL) was treated with N-bromosuccinimide (2.55
g, 14.4 mmol) in THF (60 mL) and water (20 mL), while the
temperature was kept at 0 °C. The reaction mixture was
stirred for 1 h at 0 °C, THF was removed in vacuo, and
standard workup followed by filtration over SiO2 using ethyl
acetate/hexanes (20/1) as an eluant afforded the bromohydrin
17 (3.1 g, 48%) as an oil. IR (neat): 3429, 2930, 2856, 1741,
1
(t, J ) 7.5 Hz, 1H). The H NMR spectrum was in agreement
1726, 1426, 1375, 1253, 1101, 1047, 836, 775 cm-1
.
1H NMR:
with that reported in ref 28.
δ 5.14 (m, 2H), 3.98 (m, 1H), 3.59 (t, J ) 6 Hz, 2H), 2.18-1.95
(m, 12H), 1.61 (s, 6H), 1.37 (s, 3H), 1.34 (s, 3H), 0.89 (s, 9H),
0.05 (s, 6H). The product was used without further purifica-
tion in the next reaction.
12,13-E p oxy-5,9,13-t r im e t h yl-(4E ,8E )-t e t r a d e ca d ie -
n yl 4′,8′-Dim et h yl-(3′E),7′-n on a d ien yl Su lfid e (2). To a
solution of NaOH (5.0 g, 0.12 mol) in H2O (10 mL) and toluene
(10 mL) were added tetraoctylammonium bromide (0.05 g, 0.1
mmol), thiol 23 (0.24 g, 1.3 mmol), and mesylate 20 (0.30 g,
0.87 mmol) at room temperature. The mixture was then
warmed to 40 °C and stirred overnight. Standard workup
followed by chromatography using ethyl acetate/hexanes (1/
20) as the eluant yielded 2 (0.24 g, 64%). IR (neat): 2926,
1-[(ter t-Bu tyld im eth ylsilyl)oxy]-12,13-ep oxy-5,9,13-tr i-
m eth yl-(4E,8E),12-tetr a d eca tr ien e (18). The bromohydrin
17 (3.0 g, 6.5 mmol) was added to K2CO3 (1.8 g, 13.0 mmol),
dissolved in methanol (40 mL), and stirred for 1 h. Next, most
of the methanol was removed in vacuo, and the resulting slurry
was diluted with water (20 mL). After extraction with Et2O
(4 × 30 mL), standard workup followed by chromatography
using ethyl acetate/hexanes (1/10) as the eluant yielded the
epoxide 18 (2.3 g, 90%) as a colorless oil. IR (neat): 2928, 2856,
2856, 1666, 1448, 1377, 1250, 1105, 910, 836, 776, 733 cm-1
.
1H NMR: δ 5.13 (m, 4H), 2.70 (t, J ) 6 Hz, 1H), 2.50 (m, 4H),
2.25 (m, 2H), 2.19-1.96 (m, 16H), 1.66 (s, 3H), 1.61 (sb, 9H),
1.59 (s, 3H), 1.31 (s, 3H), 1.24 (s, 3H). 13C NMR: δ 136.5,
135.7, 135.1, 134.1, 124.8, 124.2, 123.6, 122.6, 39.6, 36.3, 33.0,
32.2, 31.2, 29.8, 28.5, 27.5, 27.1, 26.6, 25.9, 24.8, 18.7, 15.9.
CIMS: m/ z 433 (M+ + 1, 20), 381 (50), 363 (24), 249 (63), 231
(100). HRMS Calcd for C28H48OS: 432.3425. Found: 432.3434.
3,8,12,16-Tetr a m eth yl-(3E,7E,11E),15-h ep ta d eca tetr a e-
n yl ter t-Bu tyld im eth ylsilyl Eth er (24). This was prepared
by the method of Dodd and Oehlschlager.8a
1462, 1378, 1253, 1100, 1006, 836, 775 cm-1 1H NMR: δ 5.15
.
(2H), 3.58 (t, J ) 6.5 Hz, 2H), 2.70 (t, J ) 6.0 Hz, 1H), 2.15-
1.96 (m, 10H), 1.59 (s, 3H), 1.54 (s, 3H), 1.29 (s, 3H), 1.25 (s,
3H), 0.95 (s, 9H), 0.05 (s, 6H). 13C NMR: δ 135.2, 134.0, 124.9,
124.2, 64.1, 62.7, 58.2, 39.6, 36.3, 33.0, 27.5, 26.7, 25.9, 24.9,
24.2, 18.7, 18.3, 16.0, 15.9, -5.4. CIMS: m/ z 382/281 (M+
+
1, 12/41), 363 (15), 250 (10), 249 (53), 232 (17), 231 (100). Anal.
(C23H44O2Si) C,H.
3-Br om o-17-[(ter t-b u t yld im et h ylsilyl)oxy]-2,6,10,16-
tetr a m eth yl-(6E,10E,14E)-h ep ta d eca tr ien -2-ol (25). This
was prepared in 39% yield from 24 by the same procedure
described for 8. IR (neat): 3454, 1666, 1462, 1383, 1255, and
1098 cm-1. CIMS: m/ z 517/515 (M+ + 1, 9.7/10.2), 385 (33.5),
383 (37.4), 367 (38.4), 365 (40.4), 303 (47.2), 285 (100), 231
(14.3), 229 (11), 205 (11.9), 203 (16.6), 191 (13.4), 189 (8.1),
135 (30.2), 133 (42.4). 1H NMR: δ 5.22-5.10 (m, 3H), 3.98
(dd, J ) 11.3, 1.6 Hz, 1H), 3.65 (t, J ) 7.2 Hz, 2H), 2.36-2.28
(m, 1H), 2.19 (t, J ) 7.2 Hz, 2H), 2.16-1.90 (m, 10H), 1.84-
1.73 (m, 1H), 1.68 (m, 1H), 1.61 (s, 3H), 1.59 (s, 6H), 1.34 (s,
3H), 1.32 (s, 3H), 0.88 (s, 9H), 0.041 (s, 6H). 13C NMR: δ 135.0,
133.1, 132.273, 126.2, 126.0, 124.5, 72.4, 70.8, 62.6, 43.1, 39.7,
38.2, 32.3, 28.3, 28.2, 26.7, 26.0, 25.9, 18.3, 16.4, 16.0, 15.9,
-5.2. Anal. (C27H51BrO2Si) C,H.
1-[(ter t-Bu tyld im eth ylsilyl)oxy]-15,16-ep oxy-3,8,12,16-
tetr a m eth yl-(3E,7E,11E)-h ep ta d eca tr ien e (26). This was
prepared in 96% yield by the same procedure as described for
9. IR (neat): 2957, 2928, 2856, 1666, 1462, 1378, 1252, 1096,
836 cm-1. CIMS: m/ z 435 (M+ + 1, 6.3), 418 (6.3), 303 (62.9),
285 (100), 259 (12.6), 191 (28.0), 163 (37.2), 155 (22.7), 149
(30.5), 135 (38.2), 123 (16.3). 1H NMR: δ 5.20-5.10 (m, 3H),
3.65 (t, J ) 7.2 Hz, 2H), 2.70 (t, J ) 6.3 Hz, 1H), 2.19 (t, J )
7.2 Hz, 2H), 2.16-1.95 (m, 12H), 1.61 (s, 6H), 1.59 (s, 3H),
1.30 (s, 3H), 1.26 (s, 3H), 0.88 (s, 9H), 0.04 (s, 6H). 13C NMR:
δ 135.3, 134.3, 132.5, 126.5, 125.2, 124.6, 64.4, 62.8, 58.4, 43.4,
39.9, 36.6, 28.6, 28.4, 27.8, 27.0, 26.2, 25.1, 19.0, 18.6, 16.7,
16.2, -5.0. Anal. (C27H50O2Si) C,H.
12,13-E p oxy-5,9,13-t r im et h yl-(4E,8E)-t et r a d eca t r ien -
1-ol (19). Silyl ether 18 (2.28 g, 6.0 mmol) was dissolved in
20 mL of a 1.0 M solution of tetrabutylammonium fluoride in
THF, and the solution was stirred for 4 h at room temperature.
The solution was diluted with water (30 mL) and extracted
with ether (4 × 20 mL). Standard workup followed by
chromatography using ethyl acetate/hexanes (1/1) as the
eluant yielded 19 (1.5 g, 94%) as a colorless oil. IR (neat):
3386, 2929, 1461, 1379, 1250, 1122, 1059, 873, 773 cm-1 1H
.
NMR: δ 5.13 (m, 2H), 3.63 (t, J ) 6.5 Hz, 2H), 2.70 (t, J ) 6.5
Hz, 1H), 2.18-1.98 (m, 10H), 1.60 (m, 8H), 1.29 (s, 3H), 1.25
(s, 3H). 13C NMR: δ 135.6, 134.1, 124.8, 123.9, 64.2, 62.7, 58.3,
39.6, 36.3, 32.8, 27.5, 26.5, 24.8, 24.2, 18.7, 16.0, 15.9. CIMS:
m/ z 268/267 (M+ + 1, 19/100), 250 (17), 249 (95), 153 (30),
137 (11), 135 (27), 127 (16), 123 (15), 111 (16), 109 (27). Anal.
(C17H30O2) C,H.
12,13-E p oxy-5,9,13-t r im e t h yl-(4E ,8E )-t e t r a d e ca d ie -
n yl Meth a n esu lfon a te (20). To a solution of epoxy alcohol
19 (0.20 g, 0.75 mmol) in CH2Cl2 (30 mL) at -50 °C were added
triethylamine (0.15 g, 1.48 mmol) and methanesulfonyl chlo-
ride (0.14 g, 1.2 mmol). The mixture was stirred at -50 °C
for 5 min and then warmed to 0 °C. The reaction mixture was
poured into water, the organic layers were separated, and the
aqueous layer was extracted with ether (3 × 30 mL). After
the combined extracts were dried over MgSO4, the solvent was
removed in vacuo and the crude mesylate 20 was used for the
next reaction without further purification.
4,8-Dim eth yl-(3E),7-n on a d ien yl Th ioa ceta te (22). To
a stirred solution of triphenylphosphine (1.56 g, 6.0 mmol) in
THF (15 mL) was added diisopropyl azodicarboxylate (1.2 g,
6.0 mmol) at 0 °C. The mixture was stirred for 0.5 h, after
which time a mixture of thioacetic acid (0.46 g, 6.0 mmol) and
homogeraniol (21)21 (0.5 g, 3.0 mmol) in THF (30 mL) was
added, while the temperature was maintained below 0 °C. The
reaction mixture was stirred for 1.5 h at 0 °C and then
15,16-Ep oxy-3,8,12,16-tetr a m eth yl-(3E,7E,11E)-h ep ta -
d eca tr ien -1-ol (27). This was prepared in 92% yield by the
procedure described for 10. IR (neat): 3418, 2955, 2927, 2852,
1667, 1448, 1379, 1250, 1049, 875 cm-1. CIMS: m/ z 321 (M+
+ 1, 61.1), 303 (100), 285 (15.6), 221 (11.7), 217 (10.6), 207
(12.6), 191 (37.1), 163 (27.5), 153 (50.3), 149 (30.4). 1H NMR:
δ 5.24 (dt, J ) 1.2, 6.3 Hz, 1H), 5.18-5.08 (m, 2H), 3.64 (dt, J
) 5.9, 6.0 Hz, 2H), 2.70 (t, J ) 6.3 Hz, 1H), 2.24 (t, J ) 6.0

208 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 2
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Hz, 2H), 2.20-1.95 (m, 12H), 1.63 (d, J ) 1.2 Hz, 3H), 1.61 (s,
3H), 1.59 (s, 3H), 1.30 (s, 3H), 1.25 (s, 3H). 13C NMR: δ 135.4,
134.1, 131.4, 127.8, 124.9, 122.5, 64.2, 60.2, 58.2, 42.8, 39.6,
36.3, 28.3, 28.1, 27.5, 26.6, 24.9, 21.0, 18.7, 16.0, 16.0, 15.8.
Anal. (C21H36O2) C,H.
15,16-Ep oxy-3,8,12,16-tetr a m eth yl-(3E,7E,11E)-h ep ta -
d eca tr ien yl Meth a n esu lfon a te (28). This was prepared in
97% yield by the procedure described for 11. Compound 28
was used in the next reaction without further purification. 1H
NMR: δ 5.30-5.00 (m, 3H), 4.27 (t, J ) 6.8 Hz, 2H), 3.00 (s,
3H), 2.70 (t, J ) 6.3 Hz, 1H), 2.42 (t, J ) 6.8 Hz, 2H), 2.25-
1.86 (m, 12H), 1.66 (s, 3H), 1.58 (s, 6H), 1.30 (s, 3H), 1.26 (s,
3H).
6-Meth yl-5-h ep ten yl-2-th ioa ceta te (30). This was pre-
pared in 84% yield by the procedure described for 13. IR
(neat): 2965, 2924, 2856, 1692, 1450, 1378, 1353, 1115, 952
cm-1. CIMS: m/ z 187 (M+ + 1, 13.4), 186 (M+, 2.3), 146 (10.3),
145 (100), 101 (3.9). 1H NMR: δ 5.07 (tq, J ) 7.2, 1.3 Hz,
1H), 3.54 (sextet, J ) 6.9 Hz, 1H), 2.30 (s, 3H), 2.04 (dt, J )
7.4, 7.4 Hz, 2H), 1.68 (s, 3H), 1.59 (s, 3H), 1.61-1.50 (m, 2H),
1.29 (d, J ) 6.9 Hz, 3H). 13C NMR: δ 195.6, 132.1, 123.4, 39.3,
36.4, 30.6, 25.6, 23.9, 21.4, 17.6. Anal. (C10H18OS) C,H.
6-Meth yl-5-h ep ten e-2-th iol (31). This was prepared in
91% yield by the procedure described for 14. IR (neat): 2966,
2921, 2850, 1667, 1449, 1376, 1115, 826 cm-1
. CIMS: m/ z
147/145 (M+ + 1, 5.6/100), 111 (12.2), 109 (1.4), 103 (4.5), 101
(19.8). 1H NMR: δ 5.07 (tq, J ) 7.2, 1.3 Hz, 1H), 2.92 (septet,
J ) 6.7 Hz, 1H), 2.09 (dt, J ) 7.2, 7.2 Hz, 2H), 1.68 (s, 3H),
1.62 (s, 3H), 1.59-1.49 (m, 2H), 1.47 (d, J ) 6.3 Hz, 1H), 1.33
(d, J ) 6.7 Hz, 3H). 13C NMR: δ 131.9, 123.4, 40.9, 35.0, 25.8,
25.5, 22.0, 17.57. Anal. (C8H16S) C,H.
15,16-Ep oxy-3,8,12,16-tetr a m eth yl-(3E,7E,11E)-h ep ta -
d eca tr ien yl 1′,5′-Dim eth yl-4′-h exen yl Su lfid e (3). This
was prepared in 74% yield by coupling of 28 and 31 according
to the procedure described for 1. IR (neat): 2960, 2922, 2855,
1667, 1449, 1376, 1248, 1119, 826 cm-1. CIMS: m/ z 447 (M+
+ 1, 100), 429 (48.8), 335 (11.4), 293 (26.8), 285 (14.6), 145
(9.2). 1H NMR: δ 5.22-5.05 (m, 4H), 2.75 (sextet, J ) 6.7
Hz, 1H), 2.70 (t, J ) 6.3 Hz, 1H), 2.57 (t, J ) 7.3 Hz, 2H), 2.23
(t, J ) 7.3 Hz, 2H), 2.20-1.95 (m, 12H), 1.68 (s, 3H), 1.65-
1.58 (m, 2H), 1.61 (s, 9H), 1.59 (s, 3H), 1.51-1.44 (m, 2H), 1.29
(s, 3H), 1.27 (d, J ) 6.8 Hz, 3H), 1.25 (s, 3H). 13C NMR: δ
135.1, 134.1, 133.8, 131.9, 125.7, 125.0, 124.3, 124.0, 64.2, 58.2,
40.2, 39.7, 39.6, 37.2, 36.4, 29.1, 28.3, 28.1, 27.6, 26.7, 25.6,
24.9, 21.4, 18.7, 17.7, 16.0, 15.9, 15.8. Anal. (C29H50OS) C,H.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada for sup-
port of this work through a research grant to A.C.O.,
the NIH Grant GM 44836 to G.D.P., and the Deutshe
Forschungsgemeinschaft (DFG) for a postdoctoral fel-
lowship to D.S.
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