Novel 1′,1′-chain substituted hexahydrocannabinols: 9β-hydroxy-3-(1-hexyl-cyclobut-1-yl)-hexahydrocannabinol (AM2389) a highly potent cannabinoid receptor 1 (CB1) agonist

Article abstract of DOI:10.1021/jm100641g

In pursuit of a more detailed understanding of the structural requirements for the key side chain cannabinoid pharmacophore, we have extended our SAR to cover a variety of conformationally modified side chains within the 9-keto and 9-hydroxyl tricyclic st

Full text of DOI:10.1021/jm100641g

6996 J. Med. Chem. 2010, 53, 6996–7010
DOI: 10.1021/jm100641g
Novel 10,10-Chain Substituted Hexahydrocannabinols: 9β-Hydroxy-3-(1-hexyl-cyclobut-1-yl)-
hexahydrocannabinol (AM2389) a Highly Potent Cannabinoid Receptor 1 (CB1) Agonist
Spyros P. Nikas,*,† Shakiru O. Alapafuja,† Ioannis Papanastasiou,† Carol A. Paronis,† Vidyanand G. Shukla,†
Demetris P. Papahatjis,‡ Anna L. Bowman,† Aneetha Halikhedkar,† Xiuwen Han,† and Alexandros Makriyannis*,†
†Center for Drug Discovery, Northeastern University, 116 Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115,
and ‡Institute of Organic and Pharmaceutical Chemistry, National Hellenic Research Foundation, 48 Vass. Constantinou, Athens 116-35, Greece
Received May 27, 2010
In pursuit of a more detailed understanding of the structural requirements for the key side chain
cannabinoid pharmacophore, we have extended our SAR to cover a variety of conformationally modified
side chains within the 9-keto and 9-hydroxyl tricyclic structures. Of the compounds described here, those
with a seven-atom long side chain substituted with a cyclopentyl ring at C10 position have very high
affinities for both CB1 and CB2 (0.97 nM<Ki <5.25 nM), with no preference for either of the two
receptors. However, presence of the smaller cyclobutyl group at the C10 position leads to an optimal
affinity and selectivity interaction with CB1. Thus, two of the C10-cyclobutyl analogues, namely,
(6aR,10aR)-3-(1-hexyl-cyclobut-1-yl)-6,6a,7,8,10,10a-hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo-
[b,d]pyran-9-one and (6aR,9R,10aR)-3-(1-hexyl-cyclobut-1-yl)-6a,7,8,9,10,10a-hexahydro-6,6-dimethyl-
6H-dibenzo[b,d]pyran-1,9 diol (7e-β, AM2389), exhibited remarkably high affinities (0.84 and 0.16 nM,
respectively) and significant selectivities (16- and 26-fold, respectively) for CB1. Compound 7e-β
was found to exhibit exceptionally high in vitro and in vivo potency with a relatively long duration of
action.
Introduction
9R-OH isomers. Interestingly, a study involving the axial (9R)
and the equatorial (9β) alcohols 1f and 1e, respectively, indicates
that only the 9β-hydroxyl isomer (1e) was an analgesic in mice.22
In earlier work, we have focused on novel (-)-Δ8-tetrahy-
drocannabinol analogues (1c) that bear cyclic moieties at the
C10-position of the side chain.23-28 This careful SAR led to
(-)-Δ8-THC analogues with high affinities for both CB1 and
CB2 cannabinoid receptors and provided a good starting
point for the development of more subtype selective second
generation ligands.
In the current study, we chose to investigate the effect of
modifying the C3 side chain in HHC’s with regard to affinity
and selectivity for the CB1 and CB2 cannabinoid receptors.
Toward this end, a number of novel side chain hexahydro-
cannabinol analogues represented by the general structure 1g
were synthesized. Our design retains the keto or hydroxyl
groups at C9 and replaces the 10,10-gem-dimethyl group with
the larger and sterically more confined cyclobutyl and cyclo-
pentyl groups as well as with the less hydrophobic dithiolane
five-membered ring. As with earlier work on the THC tem-
plate, the design of our HHC analogues has included a seven-
atom-long side chain and methyl-, bromo-, or cyano-substitu-
tion at the terminal carbon (analogues 6b, 6c, 6e, 15b, 16,
22, 7c-β, 7e-β, 23, and 24, Table 1). Additionally, we have
explored the pharmacophoric limits of side chain length
and the effects of conformational restriction at the C20-C30
bond by synthesizing the C10-cyclopentyl analogues with six-
and eight-atom-long side chains (compounds 15a and 15c,
Table 1), as well as those incorporating the respective C20-C30-
Z-heptenyl chains (compounds 6a and 6d, Table 1).
The recognition of two distinct Gi/o-protein-coupled cannabi-
noid receptors (CB1a and CB2)1-11 and the discovery of two
endogenous ligands, arachidonoylethanolamine (anandamide)12
and 2-arachidonoylglycerol,13,14 has led to efforts to define the
structural requirements for receptor specificity. A review of
structure-activity relationship (SAR) studies15-19 recognizes
two pharmacophores within the classical (-)-Δ8-tetrahydrocan-
nabinol ((-)-Δ8-THC, 1a, Figure 1) template: a phenolic hydro-
xyl (PH), and a lipophilic side chain (SC). Of these, the aliphatic
side chain was shown to play a pivotal role in determining
cannabinergic potency. Optimal activity is obtained with a seven
carbon length substituted with 10,10-dimethyl groups (1b) as was
first demonstrated by Adams.20 It has also been shown that in
hexahydrocannabinols (HHC, Figure 1) where the C-ring is fully
saturated, presence of a keto21 or a hydroxyl22 group at the C9
position (e.g., nabilone, 1d) can have significant effects on the
compound’s ability to interact with CB receptors.15-17 On the
basis of the relative configuration at the C9 position of the
9-hydroxyhexahydrocannabinols (1e, 1f), we can obtain 9β- or
*To whom correspondence should be addressed. For A.M.: phone,
þ1-617-373-4200; fax, þ1-617-373-7493; e-mail, a.makriyannis@neu.
edu. For S.P.N.: phone, þ1-617-373-3125; fax, þ1-617-373-7493;
e-mail, s.nikas@neu.edu.
a Abbreviations: CB1, cannabinoid receptor 1; CB2, cannabinoid
receptor 2; SAR, structure-activity relationship; (-)-Δ8-THC, (-)-
Δ8-tetrahydrocannabinol; PH, phenolic hydroxyl; SC, side chain;
HHC, hexahydrocannabinol; p-TSA, p-toluenesulfonic acid; K-selec-
tride, potassium tri-sec-butyl borohydride; TMSOTf, trimethylsilyl
triflate; DMSO, dimethylsulfoxide; HEK, human embryonic kidney;
NMR, nuclear magnetic resonance; DEPT, distortionless enhancement
by polarization transfer; COSY, correlation spectroscopy; HSQC,
heteronuclear single quantum correlation; HMBC, heteronuclear multi-
ple bond correlation; NOESY, nuclear Overhauser effect spectroscopy.
All synthesized analogues were tested for their respective
affinities for CB1 and CB2. Hexahydrocannabinols carrying
r
pubs.acs.org/jmc
Published on Web 09/09/2010
2010 American Chemical Society

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 6997
purification to give pure equatorial hydroxyl analogues 7c-β
and 7e-β in 85-95% yield. The stereochemistry of the hydro-
xyl groups of 7c-β/7c-r and 7e-β/7e-r isomeric pairs was
assigned on the basis of 1H NMR (500 MHz) spectral data.
Thus, incompounds7c-β and 7e-β, the peakhalf-width for the
C9protonswas foundtobe21-22 Hzwhile incompounds7c-
r and 7e-r was 10.5 Hz (see Experimental Section). This
correlates well with an axial C9 proton in the former two
compounds and an equatorial C9 proton in the latter two.
Synthesis of the C10-cyclopentyl analogues 15a-15c and 16
was accomplished by a reaction sequence shown in Scheme 2.
Commercially available phenoxyalkyl bromides 8a, 8b, and 8c
were reacted with triphenylphosphine in refluxing benzene32
to give the respective (phenoxyalkyl)triphenylphosphonium
bromides 9a, 9b, and 9c in very good yields (80-85%).
Treatment of 9a-9c with potassium bis(trimethylsilyl)amide
and coupling of the generated phosphoranes with 1-(3,5-
dimethoxyphenyl)cyclopentanecarboxaldehyde24,25,27,30 (10)
at 0 °C produced intermediate alkenes 11a-11c (91-95%),
bearing five, six, and seven carbon atom side chains, respec-
tively. On the basis of 1H NMR analysis, these Wittig
olefination reactions afforded exclusively the Z olefins with
0
0
J2 H-3 H = 11.3 Hz. Catalytic hydrogenationof11a-11cled to
the respective resorcinol dimethyl ethers 12a-12c in 94-96%
yields. Exposure of 12a-12c to boron tribromide in methy-
lene chloride cleaved all three ether groups and introduced the
C50, C60, and C70 bromo groups for 13a, 13b, and 13c,
respectively.32 Coupling with terpene acetates 3 in the pre-
sence of p-TSA (50-54% yield), and exposure of the resulting
norpinanones 14a-14c to trimethylsilyl triflate gave 9-keto-
hexahydrocannabinols 15a-15c (73-75% yield). Treatment
of bromide 15a with sodium cyanide in dimethyl sulfoxide
produced the respective side chain cyano-substituted analo-
gue 16 in 64% yield.
The C10-cyclobutyl analogues 22, 23, and 24 were synthe-
sized in a similar fashion from 1-(3,5-dimethoxyphe-
nyl)cyclobutanecarboxaldehyde (17, Scheme 3), which was
in turn obtained from commercially available 2 in five steps by
a methodology developed in our laboratories.24,25,27,30 Thus,
combination of 17 and the ylide derived from (4-phenoxybutyl)-
triphenylphosphonium bromide (9b) and potassium bis-
(trimethylsilyl)amide, resulted in the exclusive formation of
Figure 1
seven-atom-long side chains substituted with cyclobutyl and
cyclopentyl groups at the C10-position exhibited the highest
affinities for CB1 and CB2. More interestingly, within this
series the cyclobutylhexenyl (6d) and the cyclobutylhexyl (6e
and 7e-β) analogues (Table 1) were found to have remarkably
high affinities and significant selectivities (11- to 26-fold) for
CB1. The analogue with the highest CB1 binding affinity and
selectivity (7e-β, AM238929) was tested in rats for its ability to
induce hypothermia and analgesia. The compound was found
to exhibit exceptionally high in vivo potency with a relatively
long duration of action. In addition, functional characteri-
zation found 7e-β to be a potent CB1 agonist with an EC50=
1.5 ( 0.3 nM.
Chemistry
Resorcinols 4a-4e, (Scheme 1) bearing C10-cyclopentyl,
C10-dithiolanyl, and C10-cyclobutyl-ring substituents were
synthesized in four to eight steps from 3,5-dimethoxy-
benzaldehyde (2) by following our previously reported pro-
cedures.23-27,30 We have recently described the efficient synthe-
sis of the mixture of chiral terpene acetates 3, which was used
in the synthesis of (-)-Δ9-tetrahydrocannabinol and (-)-Δ9-
tetrahydrocannabivarin metabolites in their native 6aR,10aR
absolute configuration.31 This mixture served as the starting
point for the synthesis of the bicyclic intermediates 5a-5e.
Thus, coupling of resorcinol derivatives 4a-4e with 3 in the
presence of p-toluenesulfonic acid (p-TSA), under our opti-
mized reaction conditions,31 led to norpinanones 5a-5e
(24-58%). The structure of 5b was established using 1D
NMR spectra as well as 13C DEPT spectrum, COSY, HSQC,
HMBC, and NOESY correlations (available under Support-
ing Information). Dibenzo[b,d]pyran ring closure proceeded
smoothly with catalytic trimethylsilyl triflate31 to give ketones
6a-6e in 51-67% yield. Sodium borohydride reduction of
ketones 6c and 6e at -40 °C gave the corresponding equator-
ial hydroxyl compounds 7c-β and 7e-β along with traces
0
0
the Z isomer 18 in 91% yield (J2 H-3 H = 11.1 Hz). Catalytic
hydrogenation of 18 led to resorcinol dimethyl ether 19,
which was treated with boron tribromide to give the corre-
sponding resorcinol 20 in quantitative yield. Condensation
of 20 with terpene acetates 3 afforded norpinanone 21 (46%
yield) which upon treatment with catalytic trimethylsilyl
triflate gave the hexahydrocannabinol 22 in 70% isolated
yield. Sodium borohydride reduction of ketone 22 in metha-
nol (-40 °C) gave a mixture of isomeric alcohols 23 and 24 in
a 97:3 ratio, respectively (by 1H NMR). Pure equatorial
alcohol 23 was obtained by chromatographic purification in
85% yield. Reduction of 22 with potassium tri-sec-butyl
borohydride33 (K-selectride) at -78 °C was very selective
and gave the axial alcohol 24 exclusively (70% yield). The
n-pentyl-HHC 1h31 (Table 1), which carry the side chain of the
natural cannabinoid (-)-Δ9-THC, was synthesized similarly
by coupling commercially available olivetol with diacetates 3.
Results and Discussion
Receptor Binding Studies. The abilities of 1h, 6a-6e,
15a-15c, 16, 22, 7c-β, 7e-β, 23, and 24 to displace radiola-
beled CP-55,940 from purified rat forebrain synaptosomes
1
(3-4% by H NMR) of the respective axial isomers 7c-r
and 7e-r. This was followed by flash column chromatography

6998 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
Nikas et al.
Table 1. Affinities (Ki) of Hexahydrocannabinol Analogues for rCB1 and mCB2 Cannabinoid Receptors (95% Confidence Limits)
a Affinities for rCB1 and mCB2 were determined using rat brain (CB1) or mouse spleen (CB2) membranes and [3H]CP-55,940 as the radioligand
following previously described procedures.25,27,37 Data were analyzed using nonlinear regression analysis. Ki values were obtained from three
independent experiments run in duplicate and are expressed as the mean of the three values. b Reported previously.15
and mouse spleen synaptosomes were determined, as de-
scribed in the Experimental Section. Ki values calculated
from the respective displacement curves are listed in Table 1
and reflect the affinities of these hexahydrocannabinol ana-
logues for the rat CB1 (rCB1) and mouse CB2 (mCB2)
receptors.

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 6999
Scheme 1a
a Reagents and conditions: (a) 3, p-TSA, CHCl3, 0 °C to room temperature, 3 days, 24-58%; (b) TMSOTf, CH2Cl2/CH3NO2 (3:1), 0 °C to room
temperature, 3 h, 51-67%; (c) NaBH4, MeOH, -40 °C, 1.5 h, 85-95%.
Scheme 2a
a Reagents and conditions: (a) Ph3P, C6H6, reflux, 2 days, 80-85%; (b) (Me3Si)2N-Kþ, THF, 0 °C, 10 min, then 1-(3,5-dimethoxyphe-
nyl)cyclopentanecarboxaldehyde (10), 20 min, 91-95%; (c) H2, Pd/C, AcOEt, room temperature, overnight, 94-96%; (d) BBr3, CH2Cl2, -78 °C to
room temperature, 12 h, 89-93%; (e) 3, p-TSA, CHCl3, 0 °C to room temperature, 3 days, 50-54%; (f) TMSOTf, CH2Cl2/CH3NO2 (3:1), 0 °C to room
temperature, 3 h, 73-75%; (g) NaCN, DMSO, room temperature, 20 h, 64%.
The compounds included in this study are 9-keto- and
9-hydroxyl-HHC analogues in which the six- to eight-atom
long side chain pharmacophore incorporates cyclic substi-
tuents at the C10 position. As can be observed in Table 1, the
range of Ki values of the C10-ring substituted analogues,
included in this study, spans over 2 orders of magnitude. This
indicates that the size and the nature of the C10-ring sub-
stituent along with the length of the side chain can have a
profound effect on the affinities of HHC analogues for both
the CB1 and CB2 receptors.
A comparison of the binding data of n-pentyl HHC 1h and
its C10-dimethylheptyl analogue 1b suggests that presence of
the two C10-methyl groups enhances the ligand’s affinity for
both the CB1 and CB2 receptors. This interaction is opti-
mized when the geminal dimethyl substitution is modified
into a larger and sterically more confined five-membered
carbocyclic ring as seen in the cyclopentane analogue 6b.
However, the affinity is reduced when the C10-cyclopentyl
group in 6b is substituted with the bulkier dithiolane ring in
analogue 6c. This analogue now has a 4-fold lower affinity

7000 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
Nikas et al.
Scheme 3a
a Reagents and conditions: (a) PhO(CH2)4Pþ PPh3 Br-, (Me3Si)2N-Kþ, THF, 0 °C, 10 min, then addition of 17, 20 min, 91%; (b) H2, Pd/C, EtOH,
room temperature, 50 psi, 10 h, quantitative; (c) BBr3, CH2Cl2, -78 °C to room temperature, 12 h, quantitative; (d) 3, p-TSA, CHCl3, 0 °C to room
temperature, 3 days, 46%; (e) TMSOTf, CH2Cl2/CH3NO2 (3:1), 0 °C to room temperature, 3 h, 70%; (f) NaBH4, MeOH, -40 °C, 1.5 h, 85%;
(g) K-Selectride, THF, -78 °C, 2 h, 70%.
for CB1 and an even lower affinity (44-fold) for CB2.
Interestingly, this reduction in affinity is more accentuated
in CB2. Examination of the Ki values of the C10-cyclopentyl
analogues 6b and 6a indicates that while introduction of a
C20-C30 Z-double bond can be tolerated at the CB1 receptor,
it seems to somewhat reduce the side chain’s optimal inter-
action with CB2. Thus, analogue 6a has a 5-fold lower
affinity for CB2 when compared to 6b.
CB1 over CB2. Finally, a comparison of the equatorial and
the axial alcohols 23 and 24, respectively, shows that the
relative stereochemistry of the hydroxyl group at C9 does not
affect the ligand’s affinity and selectivity for CB1 and CB2.
This is an apparent incongruence in previously reported in
vivo data where the 9R-OH hexahydrocannabinol exhibitted
reduced potency compared to its 9β-OH isomer.22
In conclusion, 9-keto-hexahydrocannabinol analogues
bearing seven-atom long side chains substituted with a
cyclopentyl ring at C10 position have very high affinities
for both CB1 and CB2 (0.97 nM<Ki<5.25 nM), with no
preference for either of the two receptors. However, presence
of the smaller cyclobutyl group at C10 position of HHC’s
leads to an optimal affinity and selectivity interaction with
CB1. The above conclusion is strongly reinforced by our
results with the C10-cyclobutyl analogues 6e and 7e-β. These
compounds with Ki values of 0.84 and 0.16 nM for CB1,
respectively, are cannabinergic probes with one of the high-
est CB1 binding affinities reported to date. In addition,
compounds 6e and 7e-β shown a 16- and a 26-fold respec-
tively selectivity for CB1 over CB2.
As seen in analogue 16, replacement of the two terminal
carbon atoms of the heptyl side chain (6b) with a cyano group
is well tolerated in both the CB1 and CB2 receptors. Also,
substitution of the terminal side chain methyl group in 6b
with a bromine atom (analogue 15b) maintains affinity for
both receptors. For ω-bromo side chains (analogues 15a,
15b, 15c), extension of the seven-atom chain length to eight
(15c) retains practically all affinity for CB1 and CB2. How-
ever, the shorter, six-atom long side chain leads to an
analogue (15a) with a significant reduction in affinity for
both the CB1 and CB2 (13-fold and 5-fold, respectively).
In summary, within the 9-keto HHC’s the C10-cyclopentyl
substituted analogues appear to exhibit no significant pre-
ference for either of the two receptors. Conversely, reduction
of the size of the C10-ring substituent to a four-membered
cyclobutane ring is accompanied by a preference for CB1.
This is seen in analogue 22 in which the end carbon of the side
chain carries a bromine atom, and more so in 6d, where a C20-
C30 Z-double bond is added. Significantly, the 11-fold CB1
selectivity for the heptenyl side chain analogue 6d is further
enhanced in its heptyl counterpart 6e where the CB1 selec-
tivity is now 16-fold.
It is especially worthy of note that the side chain SAR
trends observed in this study parallel those of (-)-Δ8-THC
analogues,25,27 suggesting that THC’s and HHC’s share key
binding motifs and support the hypothesis for a subsite23-27
within CB1 and CB2 binding domain at the level of the
benzylic side chain carbon in the tetrahydrocannabinol and
hexahydrocannabinol series.
The rat,3 mouse,5,9 and human CB1 (hCB1) receptors4
have 97-99% sequence identity across species and are not
expected to exhibit variations in their Ki values. However,
mouse CB210,11 (mCB2) exhibits only 82% sequence identity
with the human clone2 (hCB2). This divergent nature of
mCB2 and hCB2 receptors could possibly result in species-
based differences in affinity.34,35 For this reason, represen-
tative HHC analogues were assayed using membranes from
HEK293 cells expressing hCB2, and the results are listed in
Table 2. We observe that the tested compounds exhibit
A comparison of the binding affinities of the C9 equatorial
hydroxyl analogues 7c-β, 7e-β, and 23 with their 9-keto
counterparts 6c, 6e, and 22, respectively, indicates that
conversion of the 9-keto group to 9β-hydroxyl group en-
hances the ligand’s affinity for both the CB1 and CB2
receptors. The most successful analogue from this modifica-
tion is the C10-cyclobutyl derivative 7e-β with a Ki of 0.16 nM
for CB1. Importantly, 7e-β exhibits a 26-fold selectivity for

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 7001
Table 2. Affinities (Ki) of Hexahydrocannabinol Analogues for hCB2
Cannabinoid Receptors (95% Confidence Limits)
compd
hCB2 (Ki, nM)a
6a
6b
7.02 ( 1.62
3.34 ( 1.31
32.6 ( 7.1
15.1 ( 4.3
11.9 ( 2.4
1.32 ( 0.27
3.02 ( 0.73
5.88 ( 1.73
5.13 ( 1.27
1.62 ( 0.45
1.63 ( 0.37
6c
6d
6e
15b
15c
22
7e-β
23
24
a Affinities for hCB2 were determined using membranes from
HEK293 cells expressing human CB2 and [3H]CP-55,940 as the radio-
ligand following previously described procedures.33 Data were analyzed
using nonlinear regression analysis. Ki values were obtained from three
independent experiments run in duplicate and are expressed as the mean
of the three values.
similar binding affinities for both the mouse and the human
CB2.
Molecular Modeling of 7e-β. A conformational search
of 7e-β in implicit water was carried out as described in the
Experimental section and found the global energy minimum
to be as shown in Figure 2. While the global minimum
conformer is not necessarily identical to that found in the
receptor binding site, it is likely that the hexyl moiety is
approximately perpendicular to the tricyclic ring system. In
this conformation the cyclobutane ring can engage in opti-
mal interactions at the putative receptor-binding subsite.
Functional Characterization of 7e-β. The functional po-
tency of 7e-β for the CB1 receptor was obtained by measur-
ing the decrease in foskolin-stimulated cAMP, as described
in the Experimental Section, and shown to be a full agonist
with EC50 = 1.5 ( 0.3 nM.
Figure 2. Accessible conformational space for the C10-cyclobutyl-
heptyl substituent of 7e-β using an energy window of 5 kcal mol-1
Heavy atoms are shown in line representation with the cyclobutane
ring highlighted in cyan. The minimum energy conformer of 7e-β is
shown in stick representation with the cyclobutylheptyl moiety
highlighted in yellow.
.
In Vivo Behavioral Characterization of 7e-β. We have
explored the in vivo potency of our more CB1 selective high
affinity analogue 7e-β in the hypothermia and analgesia
tests (detailed procedures are given under the Experimental
Section).
Body temperature was measured in isolated rats over a
6 h period following drug injection. 7e-β decreased core body
temperature in a dose-dependent manner, with a dose of
0.1 mg/kg reducing body temperature up to 4.2 ( 0.5 °C
from an average baseline of 38.48 ( 0.06 °C. At this dose, the
onset of drug effect occurred within 60-90 min after injec-
tion, although peak effects were not obtained until 300 min
after injection. Antinociception was measured using a tail-
flick procedure over a 6 h period following drug injection.
Prior to drug administration, the average baseline tail-flick
latency was 2.1 ( 0.1 s. Compound 7e-β increased tail-flick
latency over the same dose range as in the hypothermia
measurements and with a similar time course (Figure 3).
Doses of 0.01-0.3 mg/kg 7e-β had significant antinociceptive
effects, with a mean ((95%CL) ED50 value of 0.026 mg/kg
(0.020, 0.034). The onset of the antinociceptive effects oc-
curred between 60 and 120 min after injection and these effects
generally increased over the 6 h test period (Figure 4). In
comparison, the mean ((95%CL) ED50 value of morphine
was 2.8 mg/kg (2.0, 3.8) with peak effects occurring at 30-
120 min after injection and decreasing by 3 h after injection.
The antinociceptive effects of 7e-β were subsequently re-
determined in a different group of animals; in these animals
Figure 3. Effects of 7e-β (9) and morphine (O) on antinociception
(top graph) and effects of 7e-β on body temperature (bottom graph).
Symbols represent the group mean ( sem (n = 5-6 rats). Abscissa,
dose in mg/kg; top ordinate, percentage of the maximum possible
antinociceptive effect; bottom ordinate, change in body tempera-
ture. Asterisks indicate effects that are significantly different from
vehicle, **p < 0.01, *** p < 0.001.
0.1 mg/kg 7e-β alone produced 100% of the maximum
possible effect, and this was reduced to 85.4 ( 5.8% or
48.0 ( 10.9% by a 30 min pretreatment with 1.0 or 3.0 mg/kg
rimonabant (SR141716A), respectively.
Our in vivo experiments show that 7e-β has a slow onset
and long duration of action and has potent activity in assays
of hypothermia and antinociception. This compound pro-
duced full antinociceptive responses in a tail-flick assay.
These effects were suppressed by the CB1-selective antago-
nist rimonabant, thus supporting a CB1-based mechanism

7002 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
Nikas et al.
University of Illinois at Urbana;Champaign. Mass spectral
data are reported in the form of m/z (intensity relative to
base = 100). Elemental analyses were obtained in Baron Consult-
ing Co, Milford, CT, and were within (0.4% of the theoretical
values (see Supporting Information). Purities of the tested com-
pounds were determined by elemental analysis and were >95%.
(4R)-4-{4-[1-(1,2-cis-Hexen-1-yl)-cyclopentyl]-2,6-dihydroxy-
phenyl}-6,6-dimethyl-2-norpinanone (5a). To a degassed solu-
tion of 4a27 (1.25 g, 4.81 mmol) and diacetates 331 (2.14 g, ca.
75% pure by 1H NMR, 8.99 mmol) in CHCl3 (48 mL) at 0 °C,
under an argon atmosphere, was added p-toluenesulfonic acid
monohydrate (1.28 g, 6.73 mmol). The mixture was warmed to
room temperature and stirred for 3 days to ensure complete
formation of the product. The reaction mixture was diluted with
diethyl ether and washed sequentially with water, saturated
aqueous NaHCO3, and brine. The organic phase was dried over
MgSO4, and the solvent removed under reduced pressure. The
residue was chromatographed on silica gel (43% diethyl ether in
hexane), and fractions containing almost pure product (TLC)
were combined and evaporated. Further purification by recrys-
tallization from CHCl3 and hexane gave 5a as a white crystalline
solid (1.01 g, 53% yield); mp 171-173 °C. 1H NMR (500 MHz,
CDCl3) δ 6.31 (s, 2H, ArH), 5.63 (dt, J = 11.3 Hz, J = 1.5 Hz,
1H, 20-H), 5.27 (dt, J = 11.3 Hz, J = 7.5 Hz, 1H, 30-H), 4.92 (br
s, 2H, OH), 3.94 (t, J = 8.2 Hz, 1H, 4-H), 3.49 (dd, J = 18.8 Hz,
J = 7.8 Hz, 1H, 3R-H), 2.60 (dd, J = 18.9 Hz, J = 8.7 Hz, 1H,
3β-H), 2.58 (t, J = 5.1 Hz, 1H, 1-H), 2.49 (m, 1H, 7R-H), 2.46 (d,
J = 10.5 Hz, 1H, 7β-H), 2.28 (t, J = 5.2 Hz, 1H, 5-H), 1.95-1.85
(m, 4H of the cyclopentane ring), 1.76-1.65 (m, 6H, 4H of the
cyclopentane ring, 40-H), 1.36 (s, 3H, 6-Me), 1.11-1.07 (m, 4H,
50-H, 60-H), 0.99 (s, 3H, 6-Me), 0.75 (t, J = 6.7 Hz, 3H, 70-H).
13C NMR (CDCl3) δ 216.0 (C-2), 153.5 (ArC-2, ArC-6), 148.1
(ArC-4), 137.2 (>CdC<), 131.0 (>CdC<), 112.3 (ArC-1),
106.4 (ArC-3, ArC-5), 56.8, 50.5, 45.8, 41.1, 39.7, 36.8, 30.3,
28.4, 27.2, 25.1, 23.3, 22.5, 21.2, 21.0, 12.8; mass spectrum m/z
(relative intensity) 396 (Mþ, 73), 381 (10), 379 (14), 353 (29), 313
(100), 273 (21), 229 (20), 203 (27), 175 (24), 109 (16), 83 (34).
Exact mass calculated for C26H36O3, 396.2664; found, 396.2667.
Anal. (C26H36O3) C, H.
Figure 4. Effects of 7e-β at different times after injection on anti-
nociception (top graph) and body temperature (bottom graph).
Abscissa, time (in minutes) after injection; top ordinate, percentage
of the maximum possible antinociceptive effect; bottom ordinate,
change in body temperature. Asterisks indicate effects that are sig-
nificantly different from vehicle, *p < 0.05, **p < 0.01, *** p< 0.001.
for the analgesic action of 7e-β. Although similar antinoci-
ceptive effects were obtained with morphine, these were
approximately 100-fold lower than 7e-β. Furthermore, the
antinociceptive effects of 7e-β were longer lasting than were
effective doses of morphine. The hypothermic effects of 7e-β
were also profound, and peak hypothermic and antinocicep-
tive effects of 7e-β occurred over the same range of doses and
over similar time courses. However, small yet significant
antinociceptive effects of 7e-β occurred at low doses that did
not significantly lower body temperature.
(4R)-4-[4-(1-Hexyl-cyclopentyl)-2,6-dihydroxy-phenyl]-6,6-
dimethyl-2-norpinanone (5b). The synthesis was carried out as
described for 5a starting from 4b25 (1.9 g, 7.25 mmol), diacetates
331 (4.31 g, ca. 75% pure by 1H NMR, 13.57 mmol), and
p-toluenesulfonic acid monohydrate (1.93 g, 10.15 mmol) in
CHCl3 (73 mL) and gave 1.68 g (58% yield) of 5b as a white
crystalline solid; mp 187-188 °C (from CHCl3-hexane). IR
(neat) 3330, 3089, 2958, 2924, 2873, 1676 (s, >CdO), 1616,
Experimental Section
1583, 1417, 1372, 1343, 1262, 1189, 1051, 1019, 971, 841 cm-1
.
Chemistry. All reagents and solvents were purchased from
Aldrich Chemical Co., unless otherwise specified, and used
without further purification. All anhydrous reactions were
performed under a static argon or nitrogen atmosphere in
flame-dried glassware using scrupulously dry solvents. Flash
column chromatography employed silica gel 60 (230-400
mesh). All compounds were demonstrated to be homogeneous
by analytical TLC on precoated silica gel TLC plates (Merck,
60 F245 on glass, layer thickness 250 μm), and chromatograms
were visualized by phosphomolybdic acid staining. Melting
points were determined on a micromelting point apparatus and
are uncorrected. IR spectra were recorded on a Perkin-Elmer
Spectrum One FT-IR spectrometer. NMR spectra were recorded
in CDCl3, unless otherwise stated, on a Varian Mercury-300 (1H
at 300 MHz, 13C at 75 MHz) or on a Bruker Ultra Shield 400 WB
plus (1H at 400 MHz, 13C at 100 MHz) or on a Bruker DMX-500
(1H at 500 MHz, 13C at 125MHz) oron a Bruker UltraShield 700
WB plus (1H at 700 MHz, 13C at 175 MHz) spectrometers,
and chemical shifts are reported in units of δ relative to internal
TMS. Multiplicities are indicated as br (broadened), s (singlet),
d (doublet), t (triplet), q (quartet), m (multiplet), and coupling
constants (J) are reported in hertz (Hz). Low and high-resolution
mass spectra were performed in School of Chemical Sciences,
1H NMR (700 MHz, CDCl3) δ 6.22 (s, 2H, ArH), 4.97 (br s, 2H,
OH), 3.94 (t, J = 8.1 Hz, 1H, 4-H), 3.50 (dd, J = 18.8 Hz, J =
7.8 Hz, 1H, 3R-H), 2.62 (dd, J = 18.8 Hz, J = 8.6 Hz, 1H, 3β-
H), 2.59 (t, J = 5.0 Hz, 1H, 1-H), 2.51 (m, 1H, 7R-H), 2.47 (d,
J = 10.6 Hz, 1H, 7β-H), 2.31 (t, J = 5.3 Hz, 1H, 5-H), 1.84-1.75
(m, 2H of the cyclopentane ring), 1.73-1.57 (m, 6H of the
cyclopentane ring), 1.50-1.46 (m, 2H, 20-H), 1.36 (s, 3H, 6-Me),
1.26-1.11 (m, 6H, 40-H, 50-H, 60-H), 1.02-0.95 (m, 5H, 30-H,
6-Me, especially 0.99, s, 3H, 6-Me), 0.83 (t, J = 6.9 Hz, 3H, 70-
H). 13C NMR (CDCl3) δ 217.22 (C-2), 154.55 (ArC-2, ArC-6),
149.22 (ArC-4), 113.39 (ArC-1), 107.60 (ArC-3, ArC-5), 57.96
(C-1), 50.56 (C-10), 46.80 (C-5), 42.19 (C-6), 41.83 (C-20), 37.97
(C-3), 37.58 (C-80, C-110), 31.82 (C-50), 30.00 (C-40), 29.52 (C-4),
26.20 (6-CH3), 25.23 (C-30), 24.47 (C-7), 23.32 (C-90, C-100),
22.72 (C-60), 22.18 (6-CH3), 14.09 (C-70). Mass spectrum m/z
(relative intensity) 398 (Mþ, 33), 383 (7), 381 (8), 355 (13), 315
(43), 275 (17), 203 (19), 149 (28), 111 (38), 83 (66), 57 (100). Exact
mass calculated for C26H38O3, 398.2821; found, 398.2822. Anal.
(C26H38O3) C, H.
(4R)-4-[4-(2-Hexyl-1,3-dithiolan-2-yl)-2,6-dihydroxy-phenyl]-
6,6-dimethyl-2-norpinanone (5c). The synthesis was carried out
as described for 5a starting from 4c23 (879 mg, 2.95 mmol),

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 7003
1
diacetates 331 (1.54 g, ca. 80% pure by H NMR, 5.16 mmol),
and p-toluenesulfonic acid monohydrate (785 mg, 4.13 mmol) in
CHCl3 (30 mL) and gave 451 mg (35% yield) of 5c as a white
solid; mp 160-161 °C (from CHCl3-hexane). IR (neat) 3329,
2926, 2856, 1683 (s, >CdO), 1616, 1585, 1417, 1371, 1303, 1266,
1336, 1258, 1203, 1183, 1135, 1093, 1041, 966, 835 cm-1. 1H NMR
(500 MHz, CDCl3) δ 6.42 (d, J = 1.5 Hz, 1H, Ar-H), 6.31 (d, J =
1.5 Hz, 1H, Ar-H), 5.95 (br s, 1H, OH), 5.63 (d, J = 11.2 Hz, 1H,
20-H), 5.25 (dt, J = 11.2 Hz, J = 7.5Hz, 1H, 30-H), 3.97 (ddd, J =
15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H, 10eq-H), 2.87 (m as td, J =
12.0 Hz, J = 3.4 Hz, 1H, 10a-H), 2.63-2.59 (m, 1H, 8eq-H),
2.48-2.40 (m, 1H, 8ax-H), 2.18-2.12 (m, 2H, 10ax-H, 7eq-H),
1.99-1.92 (m, 3H, cyclopentane ring, 6a-H), 1.91-1.83 (m, 2H,
cyclopentane ring), 1.77-1.65 (m, 6H, 40-H, cyclopentane ring),
1.57-1.45 (m, 4H, 7ax-H, 6-Me, especially 1.47, s, 6-Me), 1.12-
1.04 (m, 7H, 50-H, 60-H, 6-Me, especially 1.11, s, 6-Me), 0.73 (t,
J = 6.8 Hz, 3H, 70-H). Mass spectrum m/z (relative intensity) 396
(Mþ, 39), 381 (3), 379 (4), 353 (16), 339 (13), 313 (44), 302 (22),
220 (16), 205 (56), 83 (100). Exact mass calculated for C26H36O3,
396.2664; found, 396.2669. Anal. (C26H36O3) C, H.
(6aR,10aR)-3-(1-Hexyl-cyclopent-1-yl)-6,6a,7,8,10,10a-hexa-
hydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one (6b).
To a stirred solution of 5b (550 mg, 1.38 mmol) in anhydrous
CH2Cl2/CH3NO2 (3:1 mixture, 28 mL) at 0 °C under an argon
atmosphere was added trimethylsilyl trifluoromethanesulfonate
(1.4 mL, 0.3 M solution in CH3NO2, 0.42 mmol). Stirring was
continued for 3 h while the temperature was allowed to rise to
25 °C. The reaction was quenched with saturated aqueous
NaHCO3/brine (1:1), and diethyl ether was added. The organic
phase was separated, the aqueous phase was extracted with
diethyl ether, and the combined organic phase was washed with
brine and dried over MgSO4. Solvent evaporation and purifica-
tion by flash column chromatography on silica gel (47% diethyl
ether-hexane) afforded 359 mg (65% yield) of the title com-
pound 6b as white foam. IR (neat) 3292 (br, OH), 2953, 2927,
2870, 1695 (s, >CdO), 1620, 1574, 1414, 1344, 1259, 1202, 1184,
1137, 1093, 1038, 838 cm-1. 1H NMR (500 MHz, CDCl3) δ 6.33
(d, J = 1.5 Hz, 1H, ArH), 6.19 (d, J = 1.5 Hz, 1H, ArH), 5.50 (br
s, 1H, OH), 3.93 (ddd, J = 15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H,
10eq-H), 2.88 (m as td, J = 12.0 Hz, J = 3.5 Hz, 1H, 10a-H),
2.62-2.58 (m, 1H, 8eq-H), 2.48-2.41 (m, 1H, 8ax-H), 2.19-
2.13 (m, 2H, 10ax-H, 7eq-H), 1.97 (m as td, J = 12.1 Hz, J = 2.7
Hz, 1H, 6a-H), 1.84-1.79 (m, 2H, cyclopentane ring), 1.74-
1.45 (m, 12H, cyclopentane ring, 7ax-H, 20-H, 6-Me, especially
1.47, s, 6-Me), 1.22-1.10 (m, 9H, 40-H, 50-H, 60-H, 6-Me,
especially 1.13, s, 6-Me), 1.01-0.91 (m, 2H, 30-H), 0.82 (t, J =
6.8 Hz, 3H, 70-H). Mass spectrum m/z (relative intensity) 398
(Mþ, 57), 383 (4), 381 (3), 356 (8), 314 (100), 302 (22), 220 (5), 204
(22), 83 (39). Exact mass calculated for C26H38O3, 398.2821;
found, 398.2822. Anal. (C26H38O3) C, H.
(6aR,10aR)-3-(2-Hexyl-1,3-dithiolan-2-yl)-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(6c). The synthesis was carried out analogous to the preparation
of 6b using 5c (180 mg, 0.41 mmol) and trimethylsilyl trifluor-
omethanesulfonate (0.4 mL, 0.3 M solution in CH3NO2, 0.12
mmol) in anhydrous CH2Cl2/CH3NO2 (3:1 mixture, 8.2 mL);
yield 67% (121 mg); white foam. IR (neat) 3252 (br, OH), 2925,
2854, 1693 (s, >CdO), 1616, 1574, 1411, 1332, 1259, 1203, 1182,
1136, 1093, 1044, 968 cm-1. 1H NMR (500 MHz, CDCl3) δ 6.76
(d, J = 1.8 Hz, 1H, ArH), 6.64 (d, J = 1.8 Hz, 1H, ArH), 5.85 (br
s, 1H, OH), 3.94 (m as d, J = 14.6 Hz, 1H, 10eq-H), 3.36-3.30 (m,
2H, -S(CH2)2S-), 3.28-3.21 (m, 2H, -S(CH2)2S-), 2.87 (m as
td, J = 11.9 Hz, J = 3.3 Hz, 1H, 10a-H), 2.63-2.59 (m, 1H, 8eq-
H), 2.48-2.40 (m, 1H, 8ax-H), 2.27 (m, 2H, 20-H), 2.18-2.14 (m,
2H, 10ax-H, 7eq-H), 1.96 (m as td, J = 11.7 Hz, J = 2.0 Hz, 1H,
6a-H), 1.56-1.45 (m, 4H, 7ax-H, 6-Me, especially 1.48, s, 6-Me),
1.26-1.19 (m, 8H, 30-H, 40-H, 50-H, 60-H), 1.12 (s, 3H, 6-Me), 0.84
(t, J = 7.0 Hz, 3H, 70-H). Mass spectrum m/z (relative intensity)
434 (Mþ, 6), 398 (2), 349 (43), 264 (20), 222 (29), 194 (13), 152
(100), 137 (67), 83 (8). Exact mass calculated for C24H34O3S2,
434.1949; found, 434.1949. Anal. (C24H34O3S2) C, H.
1207, 1051, 1022, 919, 843, 793 cm-1 1H NMR (500 MHz,
.
CDCl3) δ 6.68 (s, 2H, ArH), 5.02 (br s, 2H, OH), 3.95 (t, J = 8.2
Hz, 1H, 4-H), 3.44 (dd, J = 19.5 Hz, J = 7.8 Hz, 1H, 3R-H),
3.37-3.30 (m, 2H, -S(CH2)2S-), 3.25-3.18 (m, 2H, -S-
(CH2)2S-), 2.60 (dd, J = 19.5 Hz, J = 8.5 Hz, 1H, 3β-H),
2.58 (t, J = 4.7 Hz, 1H, 1-H), 2.53-2.49 (m, 1H, 7R-H), 2.44 (d,
J = 10.8 Hz, 1H, 7β-H), 2.30 (t, J = 5.2 Hz, 1H, 5-H), 2.26-2.22
(m, 2H, 20-H), 1.36 (s, 3H, 6-Me), 1.27-1.19 (m, 8H, 30-H, 40-H,
50-H, 60-H), 0.99 (s, 3H, 6-Me), 0.85 (t, J = 6.5 Hz, 3H, 70-H).
Mass spectrum m/z (relative intensity) 434 (Mþ, 18), 391 (2), 349
(100), 239 (9). Exact mass calculated for C24H34O3S2, 434.1949;
found, 434.1948. Anal. (C24H34O3S2) C, H.
(4R)-4-{4-[1-(1,2-cis-Hexen-1-yl)cyclobutyl]-2,6-dihydroxy-
phenyl}-6,6-dimethyl-2-norpinanone (5d). The synthesis was
carried out as described for 5a starting from 4d27 (710 mg,
2.89 mmol), diacetates 331 (1.5 g, ca. 80% pure by 1H NMR, 5.06
mmol), and p-toluenesulfonic acid monohydrate (770 mg, 4.05
mmol) in CHCl3 (29 mL) and gave 264 mg (24% yield) of 5d as a
white crystalline solid; mp 174-175 °C (from CHCl3-hexane).
IR (neat) 3280, 2955, 2926, 2870, 1674 (s, >CdO), 1615, 1581,
1417, 1374, 1348, 1301, 1263, 1192, 1053, 1016, 969, 920, 834,
754, 704 cm-1. 1H NMR (500 MHz, CDCl3) δ 6.31 (s, 2H, ArH),
5.73 (d, J = 11.0 Hz, 1H, 20-H), 5.30 (dt, J = 11.0 Hz, J = 7.5 Hz,
1H, 30-H), 4.85 (br s, 2H, OH), 3.95 (t, J = 8.1 Hz, 1H, 4-H), 3.49
(dd, J = 18.7 Hz, J = 7.8 Hz, 1H, 3R-H), 2.60 (dd, J = 18.7 Hz,
J = 8.5 Hz, 1H, 3β-H), 2.58 (t, J = 5.1 Hz, 1H, 1-H), 2.50 (m, 1H,
7R-H), 2.46 (d, J = 10.6 Hz, 1H, 7β-H), 2.43-2.38 (m, 2H of the
cyclobutane ring), 2.35-2.30 (m, 2H of the cyclobutane ring), 2.29
(t, J = 5.3 Hz, 1H, 5-H), 1.99-1.92 (m, 1H of the cyclobutane
ring), 1.90-1.85 (m, 1H of the cyclobutane ring), 1.84-1.78 (m,
2H, 40-H), 1.36 (s, 3H, 6-Me), 1.22-1.16 (m, 4H, 50-H, 60-H), 1.00
(s, 3H, 6-Me), 0.81 (t, J = 6.7 Hz, 3H, 70-H). Mass spectrum m/z
(relative intensity) 382 (Mþ, 100), 367 (16), 354 (18), 339 (29), 299
(27), 271 (43), 188 (41), 83 (44). Exact mass calculated for
C25H34O3, 382.2508; found, 382.2507. Anal. (C25H34O3) C, H.
(4R)-4-[4-(1-Hexyl-cyclobutyl)-2,6-dihydroxy-phenyl]-6,6-di-
methyl-2-norpinanone (5e). The synthesis was carried out as
with 5a by using 4e27 (514 mg, 2.07 mmol), diacetates 331 (1.077
g, ca. 80% pure by 1H NMR, 3.62 mmol), and p-toluenesulfonic
acid monohydrate (551 mg, 2.9 mmol) in CHCl3 (21 mL). Yield
49% (390 mg); white crystalline solid; mp 194-196 °C (from
CHCl3-hexane). IR (neat) 3315, 3080, 2944, 2930, 2855, 1675
(s, >CdO), 1615, 1582, 1417, 1373, 1345, 1262, 1190, 1053,
1039, 1018, 968, 837, 761 cm-1. 1H NMR (500 MHz, CDCl3) δ
6.06 (s, 2H, ArH), 4.85 (br s, 2H, OH), 3.95 (t, J = 8.1 Hz, 1H,
4-H), 3.49 (dd, J = 18.7 Hz, J = 7.8 Hz, 1H, 3R-H), 2.61 (dd,
J = 18.7 Hz, J = 8.6 Hz, 1H, 3β-H), 2.58 (t, J = 5.0 Hz, 1H,
1-H), 2.51 (m, 1H, 7R-H), 2.47 (d, J = 10.6 Hz, 1H, 7β-H), 2.30
(t, J = 5.4 Hz, 1H, 5-H), 2.26-2.20 (m, 2H of the cyclobutane
ring), 2.04-1.92 (m, 3H of the cyclobutane ring), 1.81-1.75 (m,
1H of the cyclobutane ring), 1.69-1.66 (m, 2H, 20-H), 1.36 (s,
3H, 6-Me), 1.27-1.16 (m, 6H, 40-H, 50-H, 60-H), 1.03-0.96 (m,
5H, 30-H, 6-Me, especially 0.99, s, 3H, 6-Me), 0.85 (t, J = 6þ.9
Hz, 3H, 70-H). Mass spectrum m/z (relative intensity) 384 (M ,
100), 367 (9), 341 (31), 313 (48), 301 (27), 273 (47), 176 (39), 83
(46). Exact mass calculated for C25H36O3, 384.2664; found,
384.2662. Anal. (C25H36O3) C, H.
(6aR,10aR)-3-[1-(1,2-cis-Hexen-1-yl)-cyclopent-1-yl]-6,6a,7,8,
10,10a-hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-
9-one (6a). The synthesis was carried out analogous to the
preparation of 6b (see text below) using 5a (467 mg, 1.18 mmol)
and trimethylsilyl trifluoromethanesulfonate (1.2 mL, 0.3 M
solution in CH3NO2, 0.36 mmol) in anhydrous CH2Cl2/CH3NO2
(3:1 mixture, 24 mL); yield 61% (284 mg); white foam. IR (neat)
3266 (br, OH), 2953, 2871, 1694 (s, >CdO), 1619, 1574, 1415,
(6aR,10aR)-3-[1-(1,2-cis-Hexen-1-yl)-cyclobut-1-yl]-6,6a,7,8,
10,10a-hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-
9-one (6d). The synthesis was carried out analogous to the prep-
aration of 6b using 5d (140 mg, 0.37 mmol) and trimethylsilyl

7004 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
trifluoromethanesulfonate (0.37 mL, 0.3 solution in
Nikas et al.
M
50-H, 60-H, 7ax-H, 10ax-H), 1.06 (s, 3H, 6-Me), 0.84 (t, J = 6þ.8
Hz, 3H, 70-H). Mass spectrum m/z (relative intensity) 436 (M ,
17), 351 (100), 205 (5). Exact mass calculated for C24H36O3S2,
436.2106; found, 436.2107. Anal. (C24H36O3S2) C, H. Compound
7c-r: 4.32 (m, 1H, 9eq-H, peak half-width = 10.5 Hz).
CH3NO2, 0.11 mmol) in anhydrous CH2Cl2/CH3NO2 (3:1
mixture, 7.5 mL); yield 51% (72 mg); white foam. IR (neat)
3254 (br, OH), 2954, 2931, 2870, 1694 (s, >CdO), 1617, 1574,
1414, 1337, 1259, 1202, 1183, 1135, 1093, 1039, 962, 835 cm-1
.
1H NMR (500 MHz, CDCl3) δ 6.45 (d, J = 1.5 Hz, 1H, ArH),
6.23 (d, J = 1.5 Hz, 1H, ArH), 5.74 (d, J = 11.1 Hz, 1H, 20-H),
5.34 (br s, 1H, OH), 5.27 (dt, J = 11.1 Hz, J = 7.5 Hz, 1H, 30-H),
3.90 (ddd, J = 15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H, 10eq-H),
2.87 (m as td, J = 12.5 Hz, J = 3.6 Hz, 1H, 10a-H), 2.62-2.56
(m, 1H, 8eq-H), 2.48-2.38 (m, 3H, 8ax-H, cyclobutane ring),
2.34-2.28 (m, 2H, cyclobutane ring), 2.18-2.12 (m, 2H, 10ax-
H, 7eq-H), 1.98-1.90 (m, 2H, 6a-H, cyclobutane ring), 1.89-
1.80 (m, 3H, 40-H, cyclobutane ring), 1.54-1.49 (m, 1H, 7ax-H),
1.47 (s, 3H, 6-Me), 1.20-1.15 (m, 4H, 50-H, 60-H), 1.11 (s, 3H,
6-Me), 0.79 (t, J = 6.7 Hz, 3H, 70-H). Mass spectrum m/z
(relative intensity) 382 (Mþ, 100), 354 (31), 339 (14), 311 (17),
272 (26), 201 (19). Exact mass calculated for C25H34O3,
382.2508; found, 382.2511. Anal. (C25H34O3) C, H.
(6aR,10aR)-3-(1-Hexyl-cyclobut-1-yl)-6,6a,7,8,10,10a-hexa-
hydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one (6e).
The synthesis was carried out analogous to the preparation of 6b
using 5e (218 mg, 0.57 mmol) and trimethylsilyl trifluorometha-
nesulfonate (0.57 mL, 0.3 M solution in CH3NO2, 0.17 mmol)
in anhydrous CH2Cl2/CH3NO2 (3:1 mixture, 12 mL); yield
64% (140 mg); white foam. IR (neat) 3247 (br, OH), 2925,
2856, 1694 (s, >CdO), 1619, 1575, 1415, 1358, 1259, 1203, 1183,
1138, 1093, 1053, 970, 839 cm-1. 1H NMR (500 MHz, CDCl3) δ
6.19 (d, J = 1.4 Hz, 1H, ArH), 6.02 (d, J = 1.4 Hz, 1H, ArH),
5.34 (br s, 1H, OH), 3.90 (ddd, J = 15.0 Hz, J = 3.5 Hz, J = 2.0
Hz, 1H, 10eq-H), 2.87 (m as td, J = 12.4 Hz, J = 3.4 Hz, 1H,
10a-H), 2.62-2.57 (m, 1H, 8eq-H), 2.48-2.40 (m, 1H, 8ax-H),
2.29-2.21 (m, 2H, cyclobutane ring), 2.19-2.13 (m, 2H, 10ax-
H, 7eq-H), 2.10-1.97 (m, 4H, 6a-H, cyclobutane ring),
1.82-1.73 (m, 1H, cyclobutane ring), 1.69-1.64 (m, 2H, 20-
H), 1.57-1.46 (m, 4H, 7ax-H, 6-Me, especially 1.47, s, 6-Me),
1.27-1.15 (m, 6H, 40-H, 50-H, 60-H), 1.13, s, 6-Me), 1.05-0.96
(m, 2H, 30-H), 0.84 (t, J = 6.8 Hz, 3H, 70-H). Mass spectrum m/z
(relative intensity) 384 (Mþ, 100), 356 (38), 341 (9), 313 (27), 274
(30), 203 (18). Exact mass calculated for C25H36O3, 384.2664;
found, 384.2655. Anal. (C25H36O3) C, H.
(6aR,9R,10aR)-3-(2-Hexyl-1,3-dithiolan-2-yl)-6a,7,8,9,10,10a-
hexahydro-6,6-dimethyl-6H-dibenzo[b,d]pyran-1,9 diol (7c-β). To
a solution of 6c (26 mg, 0.06 mmol) in anhydrous methanol
(1.2 mL) at -40 °C under an argon atmosphere was added
NaBH4 (8 mg, 0.21 mmol). The reaction mixture was stirred for
1.5 h at -40 °C and then quenched by the addition of saturated
NaCl solution. The mixture was warmed to room temperature,
diluted with H2O, and extracted with ethyl acetate. The organic
layer was washed with brine, dried (MgSO4) and evaporated to
a semisolid material 7c. On the basis of 1H NMR analysis, 7c is
a mixture of two isomeric alcohols 7c-r (Rf = 0.27, 45% AcOEt
in hexane) and 7c-β (Rf = 0.25, 45% AcOEt in hexane) in a ratio
4:96, respectively. Purification of this material by flash column
chromatography on silica gel (50% AcOEt in hexane) gave, in
order of elution, 3 mg of a mixture of 7c-r and 7c-β (1:2 ratio by
1H NMR) and 20 mg of pure 7c-β as a glassy substance (mp =
91-93 °C). Overall yield for 7c-β: 85% (22 mg). Compound 7c-β:
IR (neat) 3246 (br, OH), 2927, 2857, 1615, 1573, 1411, 1364, 1332,
1274, 1140, 1044, 820 cm-1. 1H NMR (500 MHz, CDCl3) δ 6.70
(d, J = 1.5 Hz, 1H, ArH), 6.59 (d, J = 1.5 Hz, 1H, ArH), 5.98 (br
s, 1H, OH), 3.87 (dddd, J = 15.5 Hz, J = 15.0 Hz, J = 4.5 Hz,
J = 4.5 Hz, 1H, 9ax-H, peak half-width =21Hz), 3.50 (m as brd,
J = 11.0 Hz, 1H, 10eq-H), 3.37-3.29 (m, 2H, -S(CH2)2S-),
3.27-3.18 (m, 2H, -S(CH2)2S-), 2.47 (ddd, J = 12.0 Hz, J =
11.5 Hz, J = 2.5 Hz, 1H, 10a-H), 2.27-2.23 (m, 2H, 20-H), 2.17
(m as br d, J = 10.6 Hz, 1H, 8eq-H), 1.91-1.85 (m as br d, J =
14.0Hz, 1H, 7eq-H), 1.49 (ddd, J = 12.0 Hz, J = 11.5 Hz, J = 2.5
Hz, 1H, 6a-H), 1.45-1.37 (m and s overlapping, 4H, 8ax-H,
6-Me, especially 1.38, s, 6β-Me), 1.30-1.09 (m, 10H, 30-H, 40-H,
(6aR,9R,10aR)-3-(1-Hexyl-cyclobut-1-yl)-6a,7,8,9,10,10a-
hexahydro-6,6-dimethyl-6H-dibenzo[b,d]pyran-1,9 Diol (7e-β).
The synthesis was carried out analogous to the preparation of
7c-β using 6e (300 mg, 0.78 mmol) and NaBH4 (104 mg, 2.74
1
mmol) in anhydrous methanol (15.6 mL). On the basis of H
NMR analysis, the crude material (7e) obtained after workup,
is a mixture of two isomeric alcohols 7e-r (Rf = 0.28, 40%
AcOEt in hexane) and 7e-β (Rf = 0.25, 40% AcOEt in hexane)
in a ratio 3:97, respectively. Purification by flash column
chromatography on silica gel (45% AcOEt in hexane) gave,
in order of elution, 36 mg of a mixture of 7e-r and 7e-β
1
(1:3 ratio by H NMR) and 260 mg of pure 7e-β as a glassy
substance (mp = 79-81 °C). Overall yield for 7e-β: 95% (287
mg). Compound 7e-β: IR (neat) 3277 (br, OH), 2924, 2855,
1620, 1572, 1454, 1414, 1360, 1271, 1185, 1140, 1052, 972, 836
cm-1. 1H NMR (500 MHz, CDCl3) δ 6.15 (d, J = 1.5 Hz, 1H,
ArH), 5.97 (d, J = 1.5 Hz, 1H, ArH), 5.24 (br s, 1H, OH), 3.86
(dddd, J = 15.5 Hz, J = 15.0 Hz, J = 4.5 Hz, J = 4.5 Hz, 1H,
9ax-H, peak half-width = 22 Hz), 3.48 (m as br d, J = 7.0 Hz,
1H, 10eq-H), 2.48 (ddd, J = 12.0 Hz, J = 11.5 Hz, J = 2.5 Hz,
1H, 10a-H), 2.30-2.21 (m, 2H, cyclobutane ring), 2.17 (m as br
d, J = 10.5 Hz, 1H, 8eq-H), 2.03-1.93 (m, 3H, cyclobutane
ring), 1.92-1.86 (m as br d, J = 14.0 Hz, 1H, 7eq-H), 1.82-
1.72 (m, 1H, cyclobutane ring), 1.70-1.64 (m, 2H, 20-H), 1.51
(ddd, J = 12.0 Hz, J = 11.5 Hz, J = 2.0 Hz, 1H, 6a-H), 1.46-
1.36 (m and s overlapping, 4H, 8ax-H, 6-Me, especially 1.39, s,
6-Me), 1.29-1.09 (m, 8H, 40-H, 50-H, 60-H, 7ax-H, 10ax-H),
1.08 (s, 3H, 6-Me), 1.04-0.96 (m, 2H, 30-H), 0.84 (t, J = 7.0 Hþz,
3H, 70-H). Mass spectrum m/z (relative intensity) 386 (M ,
100), 358 (42), 315 (22), 297 (19), 274 (15), 203 (11), 83
(16). Exact mass calculated for C25H38O3, 386.2821; found,
386.2823. Anal. (C25H38O3) C, H. Compound 7e-r: 4.25 (m,
1H, 9eq-H, peak half-width = 10.5 Hz).
(3-Phenoxypropyl)triphenylphosphonium Bromide (9a). A mix-
ture of 3-phenoxypropyl bromide (8a) (12 g, 55.8 mmol) and
triphenylphosphine (15.35 g, 58.6 mmol) in anhydrous benzene
(100 mL) was refluxed with vigorous stirring for two days under
argon. The reaction mixture was cooled to room temperature,
and the precipitating product (9a) was isolated by filtration under
reduced pressure as a white microcrystalline solid (mp 154-
1
156 °C) in 80% yield (21.3 g). H NMR (500 MHz, CDCl3) δ
7.87 (dd, J = 12.1 Hz, J = 8.0 Hz, 6H, -PPh3), 7.79 (td, J = 8.0
Hz, J = 1.4 Hz, 3H, -PPh3), 7.69 (td, J = 8.0 Hz, J = 3.5 Hz,
6H, -PPh3), 7.24 (t, J = 8.1 Hz, 2H, 3-H, 5-H, -OPh), 6.92 (t,
J = 8.1 Hz, 1H, 4-H, -OPh), 6.85 (d, J = 8.1 Hz, 2H, 2-H, 6-H,
-OPh), 4.33 (t, J = 5.4 Hz, 2H, -CH2OPh), 4.10 (dt, J = 12.4
Hz, J = 8.0 Hz, 2H, -CH2PPh3), 2.27-2.19 (m, 2H).
(4-Phenoxybutyl)triphenylphosphonium Bromide (9b). The syn-
thesis was carried out analogous to the preparation of 9a using
4-phenoxybutyl bromide (8b) (22.0 g, 96 mmol) and triphenyl-
phosphine (26.2 g, 100 mmol) in anhydrous benzene (100 mL);
yield 85% (40.0 g); white solid, m p 185-186 °C. 1H NMR (500
MHz, CDCl3) δ 7.96 (dd, J = 12.0 Hz, J = 8.0 Hz, 6H, -PPh3),
7.88 (td, J = 8.0 Hz, J = 1.5 Hz, 3H, -PPh3), 7.80 (td, J = 8.0
Hz, J = 3.5 Hz, 6H, -PPh3), 7.25 (t, J = 7.9 Hz, 2H, 3-H, 5-H,
-OPh), 6.92 (t, J = 7.9 Hz, 1H, 4-H, -OPh), 6.82 (d, J = 7.9 Hz,
2H, 2-H, 6-H, -OPh), 4.09 (t, J = 5.5 Hz, 2H, -CH2OPh), 4.01
(dt, J = 12.6 Hz, J = 8.1 Hz, 2H, -CH2PPh3), 2.25 (qt, J = 6.4
Hz, 2H), 1.93-1.85 (m, 2H).
(5-Phenoxypentyl)triphenylphosphonium Bromide (9c). The
synthesis was carried out analogous to the preparation of 9a
using 5-phenoxypentyl bromide (8c) (6.96 g, 28.63 mmol) and
triphenylphosphine (8.25 g, 31.5 mmol) in anhydrous benzene
1
(70 mL); yield 83% (12 g); white solid, mp 174-176 °C. H
NMR (500 MHz, CDCl3) δ 7.86 (dd, J = 12.1 Hz, J = 8.0 Hz,

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 7005
6H, -PPh3), 7.78 (td, J = 8.0 Hz, J = 1.5 Hz, 3H, -PPh3), 7.68
(td, J = 8.0 Hz, J = 3.5 Hz, 6H, -PPh3), 7.24 (t, J = 7.9 Hz, 2H,
3-H, 5-H, -OPh), 6.91 (t, J = 7.9 Hz, 1H, 4-H, -OPh), 6.78 (d,
J = 7.9 Hz, 2H, 2-H, 6-H, -OPh), 3.92 (t, J = 5.6 Hz, 2H,
-CH2OPh), 3.85 (dt, J = 12.5 Hz, J = 8.0 Hz, 2H, -CH2PPh3),
1.90-1.79 (m, 4H), 1.77-1.69 (m, 2H).
380 (Mþ, 29), 287 (14), 262 (7), 246 (24), 231 (26), 205 (100), 191
(22), 177 (15), 152 (27), 77 (34). Exact mass calculated for
C25H32O3, 380.2351; found, 380.2353.
3,5-Dimethoxy-1-[1-(4-phenoxybutyl)cyclopentyl]benzene (12a).
To a solution of 11a (704 mg, 2 mmol) in EtOAc (20 mL) was
added 10% Pd/C (106 mg), and the suspension stirred vigor-
ously under hydrogen atmosphere overnight at room tempera-
ture. The catalyst was removed by filtration through Celite, and
the filtrate was evaporated under reduced pressure to give the
product 12a as a colorless liquid, in 96% yield (680 mg), which
was used in the next step without further purification. 1H NMR
(300 MHz, CDCl3) δ 7.25 (t, J = 8.1 Hz, 2H, 3-H, 5-H, OPh),
6.91 (t, J = 8.1 Hz, 1H, 4-H, OPh), 6.83 (d, J = 8.1 Hz, 2H, 2-H,
6-H, OPh), 6.43 (d, J = 3.0 Hz, 2H, 2-H, 6-H, ArH) 6.29 (t, J =
3.0 Hz, 1H, 4-H, ArH), 3.83 (t, J = 7.2 Hz, 2H, 50-H), 3.78 (s,
6H, OMe), 1.95-1.51 (m, 12H, 8H of the cyclopentane ring and
4H of the 4-phenoxybutyl group), 1.21-1.11 (m, 2H of the
4-phenoxybutyl group). Mass spectrum m/z (relative intensity)
354 (Mþ, 32), 270 (13), 261 (22), 206 (100), 177 (9), 165 (20), 151
(30), 107 (16), 77 (20). Exact mass calculated for C23H30O3,
354.2195; found, 354.2198.
3,5-Dimethoxy-1-[1-(5-phenoxypentyl)cyclopentyl]benzene (12b).
The synthesis was carried out as described for 12a using 11b
(2.35 g, 6.42 mmol) and 10% Pd/C (360 mg) in EtOAc (60 mL)
to give the product 12b as a colorless liquid in 94% yield (2.22 g),
which was used in the next step without further purification. 1H
NMR (500 MHz, CDCl3) δ 7.26 (t, J = 7.9 Hz, 2H, 3-H, 5-H,
OPh), 6.91 (t, J = 7.9 Hz, 1H, 4-H, OPh), 6.84 (d, J = 7.9 Hz,
2H, 2-H, 6-H, OPh), 6.43 (d, J = 2.2 Hz, 2H, 2-H, 6-H, ArH)
6.29 (t, J = 2.2 Hz, 1H, 4-H, ArH), 3.85 (t, J = 6.5 Hz, 2H, 60-
H), 3.79 (s, 6H, OMe), 1.92-1.85 (m, 2H of the cyclopentane
ring), 1.80-1.74 (m, 2H of the cyclopentane ring), 1.73-1.61 (m,
6H, 4H of the cyclopentane ring and 2H of the 5-phenoxypentyl
group, overlapping), 1.60-1.54 (m, 2H, 20-H), 1.31 (qt, J = 7.7
Hz, 2H of the 5-phenoxypentyl group), 1.10-1.02 (m, 2H of the
5-phenoxypentyl group). Mass spectrum m/z (relative intensity)
368 (Mþ, 21), 275 (7), 248 (15), 206 (100), 165 (17), 151 (24), 77
(13). Exact mass calculated for C24H32O3, 368.2351; found,
368.2350.
3,5-Dimethoxy-1-[1-(6-phenoxyhexyl)cyclopentyl]benzene (12c).
The synthesis was carried out as described for 12a using 11c
(1.08 g, 2.84 mmol) and 10% Pd/C (162 mg) in EtOAc (25 mL)
to give the product 12c as a colorless liquid in 95% yield (1.03 g),
which was used in the next step without further purification. 1H
NMR (500 MHz, CDCl3) δ 7.26 (t, J = 7.8 Hz, 2H, 3-H, 5-H,
OPh), 6.90 (t, J = 7.8 Hz, 1H, 4-H, OPh), 6.83 (d, J = 7.8 Hz,
2H, 2-H, 6-H, OPh), 6.43 (d, J = 1.9 Hz, 2H, 2-H, 6-H, ArH)
6.29 (t, J = 1.9 Hz, 1H, 4-H, ArH), 3.88 (t, J = 6.4 Hz, 2H,
70-H), 3.78 (s, 6H, OMe), 1.93-1.87 (m, 2H of the cyclopentane
ring), 1.80-1.73 (m, 2H of the cyclopentane ring), 1.72-1.60 (m,
6H, 4H of the cyclopentane ring and 2H of the 6-phenoxyhexyl
group, overlapping), 1.59-1.53 (m, 2H, 20-H), 1.39-1.20 (m,
4H of the 6-phenoxyhexyl group), 1.09-1.01 (m, 2H of the
6-phenoxyhexyl group). Mass spectrum m/z (relative intensity)
382 (Mþ, 23), 306 (4), 289 (12), 262 (17), 220 (100), 179 (27), 165
(30), 77 (15). Exact mass calculated for C25H34O3, 382.2508;
found, 382.2505.
5-[1-(4-Bromobutyl)cyclopentyl]resorcinol (13a). To a stirred
solution of 12a (650 mg, 1.84 mmol) in dry CH2Cl2 (20 mL), at
-78 °C, under an argon atmosphere, was added boron tribro-
mide (6 mL, 1 M solution in CH2Cl2). Following the addition,
the reaction mixture was gradually warmed to room tempera-
ture and the stirring was continued at that temperature until
completion of the reaction (12 h). Unreacted boron tribromide
was destroyed by the addition of methanol and ice at 0 °C.
The mixturewas warmedtoroomtemperature, andvolatileswere
removed in vacuo. The residue was diluted with ethyl acetate
and washed with saturated NaHCO3 solution, water, and brine.
The organic layer was dried over MgSO4, filtered, and concen-
trated under reduced pressure. Purification by flash column
3,5-Dimethoxy-1-[1-(1,2-cis-4-phenoxybuten-1-yl)cyclopentyl]-
benzene (11a). To a stirred suspension of (3-phenoxypropyl)tri-
phenylphosphonium bromide (9a) (17.2 g, 36 mmol) in dry THF
(180 mL) at 0 °C, under an argon atmosphere, was added
potassium bis(trimethylsilyl)amide (7.16 g, 36 mmol). The mix-
ture was stirred for 10 min, and a solution of aldehyde 1025,27
(1.68 g, 7.2 mmol) in anhydrous THF (10 mL) was added
dropwise. The reaction was stirred for an additional 20 min
and upon completion (TLC) was quenched by the addition of
saturated aqueous NH4Cl (40 mL). The reaction mixture was
warmed to room temperature, the organic layer was separated,
and the aqueous phase was extracted with diethyl ether. The
combined organic layer was washed with brine and dried over
MgSO4, and the solvent evaporated under reduced pressure.
The residue was chromatographed through a short column of
silica gel (10% diethyl ether in hexane) to give compound 11a as
1
a colorless liquid in 91% yield (2.3 g). H NMR (300 MHz,
CDCl3) δ 7.24 (t, J = 7.9 Hz, 2H, OPh), 6.91 (t, J = 7.9 Hz, 1H,
OPh), 6.77 (d, J = 7.9 Hz, 2H, OPh), 6.54 (d, J = 2.4 Hz, 2H,
ArH), 6.28 (t, J = 2.4 Hz, 1H, ArH), 5.86 (d, J = 11.3 Hz, 1H,
20-H), 5.45 (dt, J = 11.3 Hz, J = 7.3 Hz, 1H, 30-H), 3.76 (s, 6H,
OMe), 3.70 (t, J = 6.8 Hz, 2H, 50-H), 2.23 (q, J = 6.8, 2H, 40-H),
2.10-1.89 (m, 4H of the cyclopentane ring), 1.79-1.65 (m, 4H
of the cyclopentane ring). Mass spectrum m/z (relative intensity)
352 (Mþ, 35), 258 (15), 231 (29), 205 (100), 152 (29), 77 (31).
Exact mass calculated for C23H28O3, 352.2038; found, 352.2038.
3,5-Dimethoxy-1-[1-(1,2-cis-5-phenoxypenten-1-yl)cyclopentyl]-
benzene (11b). The synthesis was carried out as described for 11a
using (4-phenoxybutyl)triphenylphosphonium bromide (9b)
(21 g, 42.8 mmol) in anhydrous THF (100 mL), potassium
bis(trimethylsilyl)amide (8.52 g, 42.8 mmol), and a solution of
1025,27 (2 g, 8.7 mmol) in anhydrous THF (10 mL). The crude
product obtained after work up was purified by flash column
chromatography on silica gel (10% diethyl ether in hexane)
to give compound 11b as a colorless liquid in 94% yield (2.99 g).
1H NMR (500 MHz, CDCl3) δ 7.25 (t, J = 8.2 Hz, 2H, OPh),
6.90 (t, J = 8.2 Hz, 1H, OPh), 6.80 (d, J = 8.2 Hz, 2H, OPh),
6.53 (d, J = 2.2 Hz, 2H, ArH) 6.27 (t, J = 2.2 Hz, 1H, ArH), 5.77
(d, J = 11.3 Hz, 1H, 20-H), 5.31 (dt, J = 11.3 Hz, J = 7.5 Hz,
1H, 30-H), 3.76 (s, 6H, OMe), 3.65 (t, J = 6.8 Hz, 2H, 60-H),
2.03-1.97 (m, 2H of the cyclopentane ring), 1.96-1.89 (m, 4H,
40-H and cyclopentane ring, overlapping), 1.76-1.65 (m, 4H of
the cyclopentane ring), 1.64-1.55 (m, 2H). Mass spectrum m/z
(relative intensity) 366 (Mþ, 57), 272 (23), 246 (36), 231 (67), 205
(100), 189 (17), 177 (23), 151 (43), 77 (33). Exact mass calculated
for C24H30O3, 366.2195; found, 366.2193.
3,5-Dimethoxy-1-[1-(1,2-cis-6-phenoxyhexen-1-yl)cyclopentyl]-
benzene (11c). The synthesis was carried out as described for 11a
using (5-phenoxypentyl)triphenylphosphonium bromide (9c)
(11.60 g, 22.95 mmol) in anhydrous THF (50 mL), potassium
bis(trimethylsilyl) amide (4.56 g, 22.95 mmol), and a solution of
1025,27 (1.07 g, 4.59 mmol) in anhydrous THF (10 mL). The
crude product obtained after work up was purified by flash
column chromatography on silica gel (10% diethyl ether in
hexane) to give compound 11c as a colorless liquid in 95% yield
(1.66 g). 1H NMR (500 MHz, CDCl3) δ 7.26 (t, J = 8.0 Hz, 2H,
OPh), 6.91 (t, J = 8.0 Hz, 1H, OPh), 6.83 (d, J = 8.0 Hz, 2H,
OPh), 6.52 (d, J = 2.1 Hz, 2H, ArH), 6.26 (t, J = 2.1 Hz, 1H,
ArH), 5.74 (d, J = 11.3 Hz, 1H, 20-H), 5.29 (dt, J = 11.3 Hz, J =
7.5 Hz, 1H, 30-H), 3.77-3.73 (t and s overlapping, 8H, OMe and
70-H), 2.04-1.97 (m, 2H of the cyclopentane ring), 1.94-1.88
(m, 2H of the cyclopentane ring), 1.80 (q, J = 7.0 Hz, 2H, 40-H),
1.75-1.65 (m, 4H of the cyclopentane ring), 1.58-1.52, (m, 2H),
1.29 (qt, J = 7.5 Hz, 2H). Mass spectrum m/z (relative intensity)

7006 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
Nikas et al.
chromatography on silica gel (50% diethyl ether in hexane)
afforded 535 mg (93% yield) of 13a as a slightly brown viscous
oil. H NMR (500 MHz, CDCl3) δ 6.32 (d, J = 2.3 Hz, 2H,
(4R)-4-{4-[1-(5-Bromopentyl)cyclopentyl]-2,6-dihydroxy-phenyl}-
6,6-dimethyl-2-norpinanone (14b). The synthesis was carried out as
described for 5a using 13b (1 g, 3.06 mmol), diacetates 331 (1.55
g, ca. 75% pure by 1H NMR, 4.90 mmol), and p-toluenesulfonic
acid monohydrate (930 mg, 4.9 mmol) in CHCl3 (30 mL); yield
53% (750 mg); white solid, mp 152-154 °C (from CHCl3-
hexane). IR (neat) 3307, 2926, 2866, 1673 (s, >CdO), 1618,
1582, 1417, 1373, 1301, 1264, 1206, 1052, 1020, 922, 836, 728
cm-1.; 1H NMR (400 MHz, CDCl3) δ 6.21 (s, 2H, ArH), 5.03 (br
s, 2H, OH), 3.95 (t, J = 8.2 Hz, 1H, 4-H), 3.48 (dd, J = 18.8 Hz,
J = 7.8 Hz, 1H, 3R-H), 3.32 (t, J = 7.2 Hz, 2H, 60-H), 2.61 (dd,
J = 18.8 Hz, J = 8.7 Hz, 1H, 3β-H), 2.58 (t, J = 5.1 Hz, 1H,
1-H), 2.52 (m, 1H, 7R-H), 2.47 (d, J = 10.6 Hz, 1H, 7β-H), 2.31,
(t, J = 5.2 Hz, 1H, 5-H), 1.88-1.60 (m, 10H, 8H of the
cyclopentane ring and 2H of the 5-bromopentyl group, over-
lapping), 1.53-1.47 (m, 2H, 20-H), 1.36 (s, 3H, 6-Me), 1.29 (qt,
J = 9.3 Hz, 2H, 5-bromopentyl group), 1.09-0.98 (m and s
overlapping, 5H, especially 1.00, s, 3H, 6-Me). Mass spectrum
m/z (relative intensity) 464 (Mþ þ 2, 16), 462 (Mþ, 17), 447 (15),
421 (14), 419 (13), 393 (12), 381 (55), 379 (57), 341 (23), 339 (24),
314 (100), 299 (12), 271 (13), 243 (32), 203 (67), 189 (24), 149 (34),
83 (74). Exact mass calculated for C25H35BrO3, 462.1770;
found, 462.1760. Anal. (C25H35BrO3) C, H.
1
ArH), 6.17 (t, J = 2.3 Hz, 1H, ArH), 4.72 (br s, 2H, OH), 3.30 (t,
J = 6.6 Hz, 2H, 50-H), 1.91-1.85 (m, 2H of the cyclopentane
ring), 1.78-1.59 (m, 8H, 6H of the cyclopentane ring and 2H
of the 4-bromobutyl group, overlapping), 1.57-1.51 (m, 2H,
20-H), 1.17-1.09 (m, 2H, 4-bromobutyl group). Mass spectrum
m/z (relative intensity) 314 (Mþ þ 2, 5), 312 (Mþ, 5), 271 (3), 233
(27), 191 (7), 177 (100), 161 (8), 149 (16), 137 (39), 123 (62), 67
(39). Exact mass calculated for C15H21BrO2, 312.0725; found,
312.0734.
5-[1-(5-Bromopentyl)cyclopentyl]resorcinol (13b). The synth-
esis was carried out as described for 13a using 12b (2.0 g, 5.43
mmol) and boron tribromide (18 mL, 1 M solution in CH2Cl2) in
anhydrous CH2Cl2 (50 mL). The crude product obtained after
work up was purified by flash column chromatography on silica
gel (50% diethyl ether in hexane) to give pure 13b as a slightly
1
brown viscous oil in 89% yield (1.58 g). H NMR (500 MHz,
CDCl3) δ 6.32 (d, J = 2.1 Hz, 2H, ArH), 6.16 (t, J = 2.1 Hz, 1H,
ArH), 4.66 (br s, 2H, OH), 3.32 (t, J = 6.8 Hz, 2H, 60-H),
1.90-1.79 (m, 2H of the cyclopentane ring), 1.78-1.59 (m, 8H,
6H of the cyclopentane ring and 2H of the 5-bromopentyl
group, overlapping), 1.54-1.49 (m, 2H, 20-H), 1.29 (qt, J =
7.5 Hz, 2H, 5-bromopentyl group), 1.05-0.96 (m, 2H, 5-bro-
mopentyl group). Mass spectrum m/z (relative intensity) 328
(Mþ þ 2, 8), 326 (Mþ, 7), 247 (13), 232 (6), 230 (6), 217 (7), 191
(4), 177 (100), 161 (7), 149 (14), 137 (16), 123 (43), 67 (24). Exact
mass calculated for C16H23BrO2, 326.0881; found, 326.0875.
5-[1-(6-Bromohexyl)cyclopentyl]resorcinol (13c). The synth-
esis was carried out as described for 13a using 12c (1.0 g, 2.62
mmol) and boron tribromide (9 mL, 1 M solution in CH2Cl2) in
anhydrous CH2Cl2 (20 mL). The crude product obtained after
work up was purified by flash column chromatography on silica
gel (50% diethyl ether in hexane) to give 13c as a slightly brown
viscous oil in 93% yield (830 mg). 1H NMR (500 MHz, CDCl3) δ
6.32 (d, J = 1.9 Hz, 2H, ArH), 6.17 (t, J = 1.9 Hz, 1H, ArH),
4.91 (br s, 2H, OH), 3.35 (t, J = 6.8 Hz, 2H, 70-H), 1.89-1.80 (m,
2H of the cyclopentane ring), 1.79-1.59 (m, 8H, 6H of the cyclo-
pentane ring and 2H of the 6-bromohexyl group, overlapping),
1.54-1.48 (m, 2H, 20-H), 1.32 (qt, J = 7.8 Hz, 2H, 6-bromohexyl
group), 1.17 (qt, J = 7.7 Hz, 2H, 6-bromohexyl group), 1.04-
0.95 (m, 2H, 6-bromohexyl group). Mass spectrum m/z (relative
intensity) 342 (Mþ þ 2, 6), 340 (Mþ, 6), 261 (12), 246 (6), 244 (6),
219 (4), 191 (4), 177 (100), 161 (5), 149 (11), 137 (17), 123 (46), 67
(29). Exact mass calculated for C17H25BrO2, 340.1038; found,
340.1031.
(4R)-4-{4-[1-(6-Bromohexyl)cyclopentyl]-2,6-dihydroxy-phenyl}-
6,6-dimethyl-2-norpinanone (14c). The synthesis was carried out as
described for 5a using 13c (800 mg, 2.35 mmol), diacetates 331
1
(1.2 g, ca. 75% pure by H NMR, 3.76 mmol), and p-toluene-
sulfonic acid monohydrate (887 mg, 3.76 mmol) in CHCl3
(25 mL); yield 50% (560 mg); white solid, mp 156-158 °C
(from CHCl3-hexane). IR (neat) 3308, 3109, 2939, 2865, 1674 (s,
>CdO), 1618, 1583, 1462, 1418, 1373, 1347, 1301, 1262, 1206,
1189, 1052, 1019, 921, 841, 725 cm-1 1H NMR (500 MHz,
.
CDCl3) δ 6.22 (s, 2H, ArH), 5.01 (br s, 2H, OH), 3.95 (t,
J = 8.2 Hz, 1H, 4-H), 3.49 (dd, J = 18.7 Hz, J = 7.5 Hz, 1H,
3R-H), 3.36 (t, J = 6.8 Hz, 2H, 70-H), 2.61 (dd, J = 18.7 Hz, J =
8.6 Hz, 1H, 3β-H), 2.59 (t, J = 5.1 Hz, 1H, 1-H), 2.52 (m, 1H,
7R-H), 2.46 (d, J = 10.6 Hz, 1H, 7β-H), 2.31, (t, J = 5.3 Hz, 1H,
5-H), 1.85-1.74 (m, 4H, 2H of the cyclopentane ring and 2H of
the 6-bromohexyl group, overlapping), 1.72-1.60 (m, 6H of the
cyclopentane ring), 1.52-1.46 (m, 2H, 20-H), 1.38-1.30 (s and m
overlapping, 5H, especially 1.36, s, 3H, 6-Me), 1.17 (qt, J = 7.8
Hz, 2H, 6-bromohexyl group), 1.04-0.96 (s and m overlapping,
5H, especially 1.00, s, 3H, 6-Me). Mass spectrum m/z (relative
intensity) 478 (Mþ þ 2, 17), 476 (Mþ, 17), 461 (18), 435 (16),
433 (16), 407 (16), 395 (67), 393 (69), 355 (24), 353 (25), 314 (91),
271 (16), 243 (35), 203 (84), 189 (32), 149 (34), 123 (23), 83 (100).
Exact mass calculated for C26H37BrO3, 476.1926; found,
476.1931. Anal. (C26H37BrO3) C, H.
(6aR,10aR)-3-[1-(4-Bromobutyl)cyclopentyl]-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(15a). The synthesis was carried out analogous to the prepara-
tion of 6b using 14a (100 mg, 0.23 mmol) and trimethylsilyl tri-
fluoromethanesulfonate (0.23 mL, 0.3 M solution in CH3NO2,
0.07 mmol) in anhydrous CH2Cl2/CH3NO2 (3:1 mixture, 5 mL);
yield 75% (75 mg); white foam. IR (neat) 3279 (br, OH), 2952,
2869, 1694 (s, >CdO), 1620, 1576, 1414, 1346, 1257, 1184, 1093,
1037, 838. 1H NMR (500 MHz, CDCl3) δ 6.33 (d, J = 1.0 Hz,
1H, ArH), 6.21 (d, J = 1.1 Hz, 1H, ArH), 5.76 (br s, 1H, OH),
3.96 (m as br d, J = 15.1 Hz, 1H, 10eq-H), 3.29 (t, J = 6.7 Hz,
2H, 50-H), 2.88 (m as td, J = 12.5 Hz, J = 3.6 Hz, 1H, 10a-H),
2.66-2.57 (m, 1H, 8eq-H), 2.50-2.42 (m, 1H, 8ax-H),
2.20-2.13 (m, 2H, 10ax-H, 7eq-H), 1.97 (m as td, J = 12.0
Hz, J = 1.7 Hz, 1H, 6a-H), 1.91-1.83 (m, 2H of the cyclopen-
tane ring), 1.78-1.43 (m, 14H, 6H of the cyclopentane ring, 20-
H, 40-H, 7ax-H, 6-Me, overlapping, especially 1.48, s, 6-Me),
1.19-1.02 (m and s overlapping, 5H, 30-H, 6-Me, especially 1.13,
s, 6-Me). Mass spectrum m/z (relative intensity) 450 (Mþ þ 2,
16), 448 (Mþ, 16), 435 (4), 433 (5), 407 (5), 369 (93), 314 (100),
286 (17), 273 (20), 259 (17), 245 (19), 229 (8), 204 (52), 189 (17),
163 (14), 149 (18), 123 (22), 83 (23), 69 (47). Exact mass
(4R)-4-{4-[1-(4-Bromobutyl)cyclopentyl]-2,6-dihydroxy-phenyl}-
6,6-dimethyl-2-norpinanone (14a). The synthesis was carried out
as described for 5a using 13a (450 mg, 1.44 mmol), diacetates 331
(730 mg, ca. 75% pure by 1H NMR, 2.3 mmol), and p-toluene-
sulfonic acid monohydrate (548 mg, 2.3 mmol) in CHCl3 (15
mL); yield 54% (350 mg); white solid, mp 180-182 °C (from
CHCl3-hexane). IR (neat) 3348, 2938, 2869, 1676 (s, >CdO),
1618, 1582, 1417, 1372, 1265, 1188, 1051, 1016, 920, 845 cm-1
.
1H NMR (500 MHz, CDCl3) δ 6.22 (s, 2H, ArH), 4.95 (br s, 2H,
OH), 3.94 (t, J = 8.2 Hz, 1H, 4-H), 3.48 (dd, J = 18.9 Hz, J =
7.6 Hz, 1H, 3R-H), 3.31 (t, J = 7.0 Hz, 2H, 50-H), 2.61 (dd, J =
18.9 Hz, J = 8.7 Hz, 1H, 3β-H), 2.59 (t, J = 5.0 Hz, 1H, 1-H),
2.52 (m, 1H, 7R-H), 2.46 (d, J = 10.6 Hz, 1H, 7β-H), 2.31, (t,
J = 5.3 Hz, 1H, 5-H), 1.87-1.79 (m, 2H of the cyclopentane
ring), 1.76-1.57 (m, 8H, 6H of the cyclopentane ring and 2H of
the 4-bromobutyl group, overlapping), 1.54-1.48 (m, 2H, 20-
H), 1.36 (s, 3H, 6-Me), 1.17-1.10 (m, 2H, 4-bromobutyl group),
1.00 (s, 3H, 6-Me). mass spectrum m/z (relative intensity)
450 (Mþ þ 2, 15), 448 (Mþ, 14), 433 (17), 407 (15), 405
(15), 379 (16), 365 (77), 314 (43), 285 (27), 259 (24), 243 (33),
203 (81), 189 (29), 149 (34), 123 (56), 83 (100). Exact mass
calculated for C24H33BrO3, 448.1613; found, 448.1604. Anal.
(C24H33BrO3) C, H.

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 7007
calculated for C24H33BrO3, 448.1613; found, 448.1607. Anal.
(C24H33BrO3) C, H.
2.65-2.57 (m, 1H, 8eq-H), 2.50-2.41 (m, 1H, 8ax-H), 2.23 (t,
J = 7.2 Hz, 2H, 50-H), 2.21-2.12 (m, 2H, 10ax-H, 7eq-H), 1.98
(m as td, J = 12.2 Hz, J = 1.6 Hz, 1H, 6a-H), 1.91-1.82 (m, 2H
of the cyclopentane ring), 1.75-1.61 (m, 6H of the cyclopentane
ring), 1.56-1.46 (m, 8H, 20-H, 40-H, 7ax-H, 6-Me, overlapping,
especially 1.48, s, 6-Me), 1.21-1.11 (m and s overlapping, 5H,
30-H, 6R-Me, especially 1.13, s, 6-Me). Mass spectrum m/z
(relative intensity) 395 (Mþ, 59), 380 (13), 368 (29), 353 (6),
327 (7), 314 (100), 285 (13), 272 (8), 245 (47), 227 (6), 215 (9), 203
(37), 177 (12), 149 (16), 115 (11), 91 (17), 69 (53). Exact mass
calculated for C25H33NO3, 395.2460; found, 395.2456. Anal.
(C25H33NO3) C, H, N.
3,5-Dimethoxy-1-[1-(1,2-cis-5-phenoxypenten-1-yl)cyclobutyl]-
benzene (18). The synthesis was carried our as described for 11a
using (4-phenoxybutyl)triphenylphosphonium bromide (9b)
(33.13 g, 67.42 mmol) in anhydrous THF (375 mL), potassium
bis(trimethylsilylamide) (13.40 g, 67.19 mmol), and a solution of
aldehyde 1727 (4.95 g, 22.47 mmol) in anhydrous THF (75 mL).
The crude product obtained after work up was purified by flash
column chromatography on silica gel (4% diethyl ether in
hexanes) to give compound 18 as a colorless liquid in 91% yield
(7.2 g). 1H NMR (500 MHz, CDCl3) δ 7.25 (t, J = 8.2 Hz, 2H,
3-H, 5-H, OPh), 6.91 (t, J = 8.2 Hz, 1H, 4-H, OPh), 6.80 (d, J =
8.2 Hz, 2H, 2-H, 6-H, OPh), 6.50 (d, J = 2.2 Hz, 2H, 2-H, 6-H,
ArH) 6.28 (t, J = 2.2 Hz, 1H, 4-H, ArH), 5.88 (d, J = 11.1 Hz,
1H, 20-H), 5.31 (dt, J = 11.1 Hz, J = 7.5 Hz, 1H, 30-H), 3.77 (s,
6H, OMe), 3.74 (t, J = 6.8 Hz, 2H, 60-H), 2.52-2.46 (m, 2H of
the cyclobutane ring), 2.39-2.33 (m, 2H of the cyclobutane
ring), 2.05-2.00 (tdd, J = 7.5 Hz, J = 7.5 Hz, J = 1.5 Hz, 2H,
40-H), 1.99-1.83 (m, 2H of the cyclobutane ring), 1.72-1.66
(quintet, J = 7.0 Hz, 2H, 50-H). Mass spectrum m/z (relative
intensity) 352 (Mþ, 71), 324 (9), 259 (19), 231 (58), 217 (45), 203
(70), 189 (100), 177 (14), 151 (32), 77 (23). Exact mass calculated
for C23H28O3, 352.2038; found, 352.2031.
(6aR,10aR)-3-[1-(5-Bromopentyl)cyclopentyl]-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(15b). The synthesis was carried out analogous to the prepara-
tion of 6b using 14b (200 mg, 0.43 mmol) and trimethylsilyl
trifluoromethanesulfonate (0.43 mL, 0.3 M solution in CH3-
NO2, 0.13 mmol) in anhydrous CH2Cl2/CH3NO2 (3:1 mixture,
10 mL); yield 73% (146 mg), white foam. IR (neat) 3282 (br,
OH), 2933, 2869, 1695 (s, >CdO), 1620, 1575, 1414, 1345, 1257,
1184, 1093, 1037, 837. 1H NMR (500 MHz, CDCl3) δ 6.32 (d,
J = 1.1 Hz, 1H, ArH), 6.21 (d, J = 1.1 Hz, 1H, ArH), 5.80 (br s,
1H, OH), 3.96 (ddd, J = 15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H,
10eq-H), 3.29 (t, J = 6.8 Hz, 2H, 60-H), 2.88 (m as td, J = 12.6
Hz, J = 3.6 Hz, 1H, 10a-H), 2.65-2.57 (m, 1H, 8eq-H), 2.49-
2.40 (m, 1H, 8ax-H), 2.19-2.12 (m, 2H, 10ax-H, 7eq-H), 1.97
(m as td, J = 12.0 Hz, J = 1.8 Hz, 1H, 6a-H), 1.87-1.79 (m, 2H
of the cyclopentane ring), 1.77-1.58 (m, 8H, 6H of the cyclo-
pentane ring and 2H of the 5-bromopentyl group, overlapping),
1.57-1.45 (m and s overlapping, 6H, 7ax-H, 20-H, 6-Me,
especially 1.47, s, 6-Me), 1.28 (qt, J = 7.5 Hz, 2H, 5-bromo-
pentyl group), 1.12 (s, 3H, 6-Me), 1.07-0.98 (m, 2H, 5-bromo-
pentyl group). Mass spectrum m/z (relative intensity) 464 (Mþ þ
2, 10), 462 (Mþ, 10), 449 (3), 447 (3), 383 (14) 353 (10), 314 (100),
299 (7), 273 (4), 245 (8), 204 (27), 189 (8), 175 (5), 149 (13), 83
(11), 69 (37). Exact mass calculated for C25H35BrO3, 462.1770;
found, 462.1767. Anal. (C25H35BrO3) C, H.
(6aR,10aR)-3-[1-(6-Bromohexyl)cyclopentyl]-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(15c). The synthesis was carried out analogous to the prepara-
tion of 6b using 14c (150 mg, 0.31 mmol) and trimethylsilyl tri-
fluoromethanesulfonate (0.30 mL, 0.3 M solution in CH3NO2,
0.09 mmol) in anhydrous CH2Cl2/CH3NO2 (3:1 mixture, 7 mL);
yield 74% (111 mg), white foam. IR (neat) 3292 (br, OH), 2932,
2869, 1695 (s, >CdO), 1620, 1574, 1414, 1345, 1264, 1184, 1092,
1037, 838. 1H NMR (500 MHz, CDCl3) δ 6.32 (d, J = 1.4 Hz,
1H, ArH), 6.23 (d, J = 1.4 Hz, 1H, ArH), 5.99 (br s, 1H, OH),
3.99 (m as br d, J = 15.1 Hz, 1H, 10eq-H), 3.33 (t, J = 6.9 Hz,
2H, 70-H), 2.89 (m as td, J = 12.6 Hz, J = 3.5 Hz, 1H, 10a-H),
2.65-2.57 (m, 1H, 8eq-H), 2.49-2.41 (m, 1H, 8ax-H), 2.19-
2.13 (m, 2H, 10ax-H, 7eq-H), 1.97 (m as td, J = 12.0 Hz, J = 1.6
Hz, 1H, 6a-H), 1.87-1.80 (m, 2H of the cyclopentane ring),
1.79-1.60 (m, 8H, 6H of the cyclopentane ring and 2H of the
6-bromohexyl group, overlapping), 1.59-1.45 (m and s over-
lapping, 6H, 7ax-H, 20-H, 6-Me, especially 1.47, s, 6-Me), 1.32
(qt, J = 7.5 Hz, 2H, 6-bromohexyl group), 1.16 (qt, J = 7.6 Hz,
2H, 6-bromohexyl group), 1.12 (s, 3H, 6-Me), 1.08-0.99 (m,
2H, 6-bromohexyl group). Mass spectrum m/z (relative in-
tensity) 478 (Mþ þ 2, 5), 476 (Mþ, 5), 465 (3), 463 (3), 447 (4),
397 (10), 381 (14), 379 (15), 341 (6), 339 (7), 314 (100), 299 (4),
220 (7), 205 (42), 189 (15), 149 (18), 83 (28), 69 (43). Exact mass
calculated for C26H37BrO3, 476.1926; found, 476.1918. Anal.
(C26H37BrO3) C, H.
3,5-Dimethoxy-1-[1-(5-phenoxypentyl)cyclobutyl]benzene (19).
To a solution of alkene 18 (7.9 g, 22.41 mmol) in absolute EtOH
(80 mL) was added Pd (10% on activated carbon, 1.4 g), and the
resulting suspension was hydrogenated under pressure (50 psi)
at room temperature for 10 h. The catalyst was removed by
filtration through Celite, and the filtrate was evaporated under
vacuum to give 7.88 g (quantitative yield) of liquid alkane 19,
which was used in the next step without further purification. 1H
NMR (500 MHz, CDCl3) δ 7.24 (t, J = 7.5 Hz, 2H, 3-H, 5-H,
OPh), 6.90 (t, J = 7.5 Hz, 1H, 4-H, OPh), 6.84 (d, J = 7.5 Hz,
2H, 2-H, 6-H, OPh), 6.27-6.25 (m, 3H, 2-H, 4-H, 6-H, ArH),
3.86 (t, J = 7 Hz, 2H, 60-H), 3.76 (s, 6H, OMe), 2.34-2.28 (m,
2H of the cyclobutane ring), 2.09-1.98 (m, 3H of the cyclobu-
tane ring), 1.83-1.74 (m, 3H, 1H of the cyclobutane ring and
20-H), 1.69 (quintet, J = 7.5 Hz, 2H, 50-H), 1.35 (quintet, J = 7.5
Hz, 2H, 40-H), 1.12-1.06 (m, 2H, 30-H). Mass spectrum m/z
(relative intensity) 354 (Mþ, 82), 326 (14), 277 (10), 261 (12), 233
(45), 205 (100), 192 (42), 178 (53), 165 (29), 151 (39), 77 (12).
Exact mass calculated for C23H30O3, 354.2195; found, 354.2190.
5-[1-(5-Bromopentyl)cyclobutyl]resorcinol (20). The synthesis
was carried our as described for 13a using 19 (7.59 g, 21.41
mmol) and boron tribromide (94 mL, 1 M solution in CH2Cl2) in
anhydrous CH2Cl2 (350 mL). The crude product obtained after
work up was purified by flash column chromatography on silica
gel (25% ethyl acetate in hexane) to give 20 as a slightly brown
(6aR,10aR)-3-[1-(4-Cyanobutyl)cyclopentyl]-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(16). To a stirred solution of 15a (50 mg, 0.11 mmol) in DMSO
(2 mL), at room temperature, under an argon atmosphere, was
added NaCN (27 mg, 0.55 mmol). After stirring at the same
temperature for 20 h, the reaction mixture was cooled to 0 °C
and diluted with water. The mixture was extracted with diethyl
ether and the organic layer was washed with brine, dried over
MgSO4, and the solvent was removed in vacuo. The residue was
purified by flash column chromatography on silica gel (70%
EtOAc in hexane) to give 16 as a white foam in 64% yield (28
mg). IR (neat) 3376, 2946, 2869, 2243 (w, CN), 1695 (s, >CdO),
1621, 1575, 1509, 1453, 1385, 1355, 1258, 1184, 1136, 1093,
1037, 948, 839. 1H NMR (500 MHz, CDCl3) δ 6.32 (d, J = 1.5
Hz, 1H, ArH), 6.22 (d, J = 1.5 Hz, 1H, ArH), 5.99 (br s, 1H,
OH), 3.97 (ddd, J = 15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H, 10eq-
H), 2.88 (m as td, J = 12.7 Hz, J = 3.5 Hz, 1H, 10a-H),
1
viscous oil in quantitative yield (6.7 g). H NMR (500 MHz,
CDCl3) δ 6.15 (s, 3H, ArH), 4.70 (br s, 2H, OH), 3.33 (t, J = 6.5
Hz, 2H, 60-H), 2.30-2.24 (m, 2H of the cyclobutane ring), 2.06-
2.00 (m, 3H of the cyclobutane ring), 1.84-1.76 (m, 3H, 2H of
5-bromopentyl group and 1H of cyclobutane ring), 1.75-1.71
(m, 2H, 20-H), 1.33 (quintet, J = 7.0 Hz, 2H, 5-bromopentyl
group), 1.06-0.99 (m, 2H, 5-bromopentyl group). Exact mass
calculated for C15H21BrO2, 312.0725; found, 312.0731.
(4R)-4-{4-[1-(5-Bromopentyl)cyclobutyl]-2,6-dihydroxy-phenyl}-
6,6-dimethyl-2-norpinanone (21). The synthesis was carried out as
described for 5a using 20 (5.8 g, 18.5 mmol), diacetates 331 (6.86 g,

7008 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19
Nikas et al.
ca. 90% pure by 1H NMR, 28.8 mmol), and p-toluenesulfonic
acid monohydrate (4.93 g, 25.9 mmol) in CHCl3 (370 mL);
yield 46% (3.8 g), white solid, mp 164-165 °C (dec) (from
CHCl3-hexane). IR (neat) 3368 (OH), 2936 (CH aromatic),
1684 (>CdO), 1620, 1585 cm-1. 1H NMR (500 MHz, CDCl3)
δ 6.06 (s, 2H, 3-H, 5-H, ArH), 5.04 (br s, 2H, OH), 3.95 (t,
J = 8.1 Hz, 1H, 4-H), 3.49 (dd, J = 18.7 Hz, J = 7.8 Hz, 1H,
3R-H), 3.35 (t, J = 6.5 Hz, 2H, 60-H), 2.61 (dd, J = 18.7 Hz, J =
8.6 Hz, 1H, 3β-H), 2.59 (t, J = 5.0 Hz, 1H, 1-H), 2.52 (m, 1H,
7R-H), 2.47 (d, J = 10.6 Hz, 1H, 7β-H), 2.31 (t, J = 5.4 Hz, 1H,
5-H), 2.28-2.20 (m, 2H of the cyclobutane ring), 2.06-1.95 (m,
3H of the cyclobutane ring), 1.84-1.74 (m, 3H, 50-H, cyclobu-
tane ring), 1.72-1.67 (m, 2H, 20-H), 1.37 (s, 3H, 6-Me), 1.34
(quintet, J = 8.0 Hz, 2H, 40-H), 1.08-1.01 (m, 2H, 30-H), 1.00
(s, 3H, 6-Me). 13C NMR (175 MHz, CDCl3) δ 217.75 (>CdO),
154.95 (ArC-2, ArC-6), 150.44 (ArC-4), 113.49 (ArC-1), 106.49
(ArC-3, ArC-5), 58.11 (C-1), 46.95 (C-5), 46.17 (C-10), 42.38 (C-
6 or C-20), 42.34 (C-20 or C-6), 38.09 (C-3), 34.22 (C-60), 32.93
(cyclobutane ring or C-50), 32.85 (cyclobutane ring or C-50),
32.81 (cyclobutane ring or C-50), 29.67 (C-4), 28.76 (C-40),
26.35 (6-Me), 24.62 (C-7), 24.04 (C-30), 22.34 (6-Me), 15.95
(cyclobutane ring). Mass spectrum m/z (relative intensity) 450
(Mþ þ 2, 55), 448 (Mþ, 55), 69 (100). Exact mass calculated for
C24H33BrO3, 448.1613; found, 448.1621.
5.09 (br s, 1H, ArOH), 3.86 (dddd, J = 15.5 Hz, J = 15.0 Hz,
J = 4.5 Hz, J = 4.5 Hz, 1H, 9ax-H, peak half-width =22 Hz),
3.47 (dddd, J = 12.0 Hz, J = 4.5 Hz, J = 2.5 Hz, J = 2.0 Hz,
1H, 10eq-H), 3.35 (t, J = 7.0 Hz, 2H, 60-H), 2.48 (ddd, J = 12.0
Hz, J = 11.5 Hz, J = 2.5 Hz, 1H, 10a-H), 2.32-2.23 (m, 2H,
cyclobutane ring), 2.17 (m as br d, J = 9.0 Hz, 1H, 8eq-H),
2.04-1.93 (m, 3H, cyclobutane ring), 1.90 (dddd, J = 13.5 Hz,
J = 3.5 Hz, J = 2.5 Hz, J = 2.0 Hz, 1H, 7eq-H), 1.82-1.74 (m
and quintet overlapping, 3H, 50-H, cyclobutane ring, especially
1.78, quintet, J = 7.0 Hz, 50-H), 1.69 (m, 2H, 20-H), 1.51 (ddd,
J = 12.0 Hz, J = 11.5 Hz, J = 2.5 Hz, 1H, 6a-H), 1.42 (dddd,
J = 15.5 Hz, J = 15.0 Hz, J = 13.0 Hz, J = 3.5 Hz, 1H, 8ax-H),
1.39 (s, 3H, 6-Me), 1.32 (quintet, J = 8.0 Hz, 2H, 40-H), 1.16
(dddd, J = 13.5 Hz, J = 13.0 Hz, J = 12.0 Hz, J = 3.5 Hz, 1H,
7ax-H), 1.12 (ddd, J = 15.5 Hz, J = 12.0 Hz, J = 12.0 Hz, 1H,
10ax-H), 1.08 (s, 3H, 6-Me), 1.07-1.00 (m, 2H, 30-H). 13C NMR
(100 MHz, CDCl3) δ 154.92 (ArC), 154.43 (ArC), 150.86 (ArC),
109.52 (ArC), 108.05 (C-2 or C-4), 106.84 (C-4 or C-2), 71.43 (C-
9), 48.47 (C-6a), 46.22 (C-6), 41.72 (C-20), 38.61 (C-10), 35.98 (C-
8), 34.26 (C-60), 34.21 (C-10), 33.41 (C-10a), 33.02 (C-50), 32.65
(cyclobutane ring), 29.32 (C-40), 27.73 (6-Me), 26.22 (C-7), 24.03
(C-30), 19.23 (6-Me), 15.92 (cyclobutane ring). Mass spectrum
m/z (relative intensity) 452 (Mþ þ 2, 45), 450 (Mþ, 45), 422 (23),
406 (119), 315 (57), 189 (38), 62 (100). Exact mass calculated for
C24H35BrO3, 450.1770; found, 450.1775. Anal. (C24H35BrO3) C, H.
(6aR,9S,10aR)-3-[1-(5-Bromopentyl)cyclobutyl]-6a,7,8,9,10,
10a-hexahydro-6,6-dimethyl-6H-dibenzo[b,d]pyran-1,9 diol (24).
To a stirred solution of ketone 22 (703 mg, 1.56 mmol) in
anhydrous THF (80 mL) was added K-Selectride (4.69 mL,
1 M solution in THF), under an argon atmosphere, at -78 °C.
Stirring was continued at that temperature for 2 h, and then the
reaction was quenched by the addition of brine. The organic
phase was separated, and the pH of the aqueous phase was
adjusted to 4-5 using a 5% solution of hydrochloric acid. The
aqueous phase was extracted with EtOAc, and the combined
organic layer was washed with brine, dried over MgSO4, and
evaporated to give an oily residue, which was further purified by
Biotage column chromatography (30% ethyl acetate in hexanes)
to afford 490 mg (70% yield) of 24 as a white solid; mp 41-
(6aR,10aR)-3-[1-(5-Bromopentyl)cyclobutyl]-6,6a,7,8,10,10a-
hexahydro-1-hydroxy-6,6-dimethyl-9H-dibenzo[b,d]pyran-9-one
(22). The synthesis was carried out analogous to the preparation
of 6b using 21 (2.0 g, 4.45 mmol) and trimethylsilyl trifluoro-
methanesulfonate (4.45 mL, 0.3 M solution in CH3NO2, 1.34
mmol) in anhydrous CH2Cl2/CH3NO2 (3:1 mixture, 90 mL);
yield 70% (1.4 g), white foam, mp 69-70 °C. IR (neat) 3292
(OH), 2932 (CH aromatic), 1693(>CdO), 1619, 1575 cm-1
.
1H NMR (500 MHz, CDCl3) δ 6.17 (d, J = 1.5 Hz, 1H, ArH),
6.03 (d, J = 1.5 Hz, 1H, ArH), 5.69 (br s, 1H, OH), 3.95 (ddd,
J = 15.0 Hz, J = 3.5 Hz, J = 2.0 Hz, 1H, 10eq-H), 3.33 (t, J =
7.0 Hz, 2H, 60-H), 2.88 (ddd, J = 14.0 Hz, J = 13.5 Hz, J = 3.5
Hz, 1H, 10a-H), 2.65-2.58 (m, 1H, 8eq-H), 2.45 (ddd, J = 15.5
Hz, J = 13.5 Hz, J = 7.5 Hz, 1H, 8ax-H), 2.32-2.23 (m, 2H,
cyclobutane ring), 2.21-2.13 (m, 2H, 10ax-H, 7eq-H),
2.22-1.92 (m, 4H, 6a-H, cyclobutane ring), 1.82-1.74 (m, 3H,
50-H, cyclobutane ring), 1.73-1.68 (m, 2H, 20-H), 1.52 (dddd,
J = 15.0 Hz, J = 13.5 Hz, J = 13.0 Hz, J = 5.0 Hz, 1H, 7ax-H),
1.48 (s, 3H, 6-Me), 1.32 (quintet, J = 7.5 Hz, 2H, 40-H), 1.13 (s,
3H, 6-Me), 1.08-1.00 (m, 2H, 30-H). 13C NMR (100 MHz,
CDCl3) δ 214.93 (>CdO), 155.43 (ArC), 154.53 (ArC), 151.43
(ArC), 107.96 (ArC), 107.20 (ArC-2 or ArC-4), 105.57 (ArC-4 or
ArC-2), 47.76 (C-6a), 46.54 (C-10), 45.35 (C-10), 42.48 (C-20),
41.18 (C-8), 35.16 (C-10a), 34.38 (C-60), 33.12 (cyclobutane ring
or C-50), 33.07 (cyclobutane ring or C-50), 32.96 (cyclobutane
ring or C-50), 28.95 (C-40), 28.21 (6-CH3), 27.25 (C-7), 24.14
(C-30), 19.23 (6-CH3), 16.12 (cyclobutane ring). Mass spectrum
m/z (relative intensity) 450 (Mþ þ 2, 77), 448 (Mþ, 77), 422 (33),
420 (33), 369 (82), 313 (78), 203 (55), 69 (100). Exact mass
calculated for C24H33BrO3, 448.1613; found, 448.1606. Anal.
(C24H33BrO3) C, H.
43 °C. IR(neat) 3337 (OH), 2930 (CH aromatic), 1620, 1568 cm-1
.
1H NMR (500 MHz, CDCl3) δ 7.14 (br s, 1H, ArOH), 6.14 (d,
J = 1.5 Hz, 1H, ArH), 6.10 (d, J = 1.5 Hz, 1H, ArH), 4.30 (m as
br s, 1H, 9eq-H, peak half-width =10.5 Hz), 3.33 (t, J = 7.0 Hz,
2H, 60-H), 3.25 (ddd, J = 14.5 Hz, J = 3.0 Hz, J = 2.5 Hz, 1H,
10eq-H), 2.95 (ddd, J = 12.0 Hz, J = 11.0 Hz, J = 2.5 Hz, 1H,
10a-H), 2.30-2.21 (m, 2H, cyclobutane ring), 2.02-1.92 (m, 4H,
8eq-H, cyclobutane ring), 1.82-1.72 (m, 3H, 50-H, cyclobutane
ring), 1.71-1.60 (m, 4H, 20-H, 8ax-H, 7-H), 1.57-1.49 (m, 2H, 6a-
H, 7-H), 1.42-1.26 (m, s and quintet overlapping, 6H, 6-Me, 40-H,
10ax-H, especially 1.37, s, 6-Me and 1.30, quintet, J = 7.5 Hz, 40-
H), 1.08-0.98 (m and s overlapping, 5H, 6-Me, 30-H, especially
1.04, s, 6-Me). 13C NMR (175 MHz, CDCl3) δ 154.80 (ArC),
154.39 (ArC), 150.46 (ArC), 109.46 (ArC), 107.85 (C-2 or C-4),
105.96 (C-4 or C-2), 67.33 (C-9), 49.46 (C-6a), 46.29 (C-6), 42.34
(C-20), 36.48 (C-10), 34.23 (C-60), 33.47 (C-8), 32.93 (C-50, C-10),
32.68 (cyclobutane ring), 29.00 (C-10a), 28.78 (C-40), 27.69 (6-
Me), 23.95 (C-30), 22.84 (C-7), 19.12 (6-Me), 15.93 (cyclobutane
ring). Mass spectrum m/z (relative intensity) 452 (Mþ þ 2, 53), 450
(Mþ, 53), 422 (18), 406 (15), 389 (12), 371 (54), 315 (42), 189 (31),
149 (40), 62 (100). Exact mass calculated for C24H35BrO3,
450.1770; found, 450.1770. Anal. (C24H35BrO3) C, H.
Radioligand Binding Assays. Forebrain synaptosomal mem-
branes were prepared from frozen rat brains by the method
described by Dodd et al.36 and were used to assess the affinities
of the novel analogues for the CB1 binding sites, while affinities
for the CB2 sites were measured using a membrane preparation
from frozen mouse spleen using a similar procedure.37 Mem-
brane preparations from HEK293 cells expressing human CB2
(hCB2) receptor were used to assess the affinities of representa-
tive analogues for hCB2.33 The displacement of specifically
(6aR,9R,10aR)-3-[1-(5-Bromopentyl)cyclobutyl]-6a,7,8,9,10,
10a-hexahydro-6,6-dimethyl-6H-dibenzo[b,d]pyran-1,9 diol (23).
The synthesis was carried out analogous to the preparation of
7c-β using 22 (200 mg, 0.445 mmol) and NaBH4 (59 mg, 1.56
mmol) in anhydrous methanol (10 mL). On the basis of 1H
NMR analysis, the crude material obtained after the workup is a
mixture of two isomeric alcohols 24 (Rf = 0.30, 40% AcOEt in
hexane) and 23 (Rf = 0.27, 40% AcOEt in hexane) in a ratio
3:97, respectively. Purification by flash column chromatogra-
phy on silica gel (45% AcOEt in hexane) gave, in order of
elution, 24 mg of a mixture of 24 and 23 (1:3 ratio by 1H NMR)
and 153 mg of pure 23 as a glassy substance (mp = 59-60 °C).
Overall yield for 23: 85% (171 mg). IR (neat) 3328 (OH), 2932
(CH aromatic), 1622, 1574 cm-1. 1H NMR (500 MHz, CDCl3) δ
6.15 (d, J = 2.0 Hz, 1H, ArH), 5.97 (d, J = 2.0 Hz, 1H, ArH),

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 19 7009
tritiated CP-55,940 from these membranes was used to deter-
mine the IC50 values for the test compounds. The assay was
conducted in a 96-well microfilter plate. The samples were
filtered using a Packard Filtermate harvester and Whatman
GF/B Unifilter-96 plates, and 0.5% BSA was incorporated into
the wash buffer. Radioactivity was detected using MicroScint 20
scintillation cocktail added to the dried filter plates and was
counted using a Packard Instruments Top Count. Data were
collected from three independent experiments between 100%
and 0% specific binding for [3H]CP-55,940, determined using
0 and 100 nM CP-55,940. The normalized data from three
independent experiments were combined and analyzed using a
four-parameter logistic equation to yield IC50 values that were
converted to Ki values using the assumptions of Cheng and
Prussoff.38
latency of 6.0 s was imposed to avoid damage to the tail. Two
baseline tail-flick latencies were obtained in each rat at 10 min
intervals, and drugs were injected immediately after the second
baseline was recorded. Tail-flick responses were recorded at
30, 60, 120, 180, and 360 min after injection.
Drugs. Compound 7e-β was initially dissolved in a solution
of 20% ethanol, 20% alkamuls, and 60% saline, and was further
diluted with saline. Morphine sulfate was dissolved in saline.
Injections were administered sc in a volume of 1.0 mL/kg, and
drug doses are expressed as the weight of the free base.
Data Analysis. For each rat, the two baseline values recorded
prior to drug injection were averaged to obtain a single baseline
value. Temperatures recorded after drug injection were ex-
pressed as a change from baseline, calculated for each animal
by subtracting the baseline temperature from the temperatures
recorded postinjection. Tail-flick responses are expressed as a
percentage of the maximum possible effect (%MPE) calculated
according to the equation: 100 ꢀ (test latency-baseline latency)/
(6-baseline latency), where 6 represents the cutoff latency. Dose-
effect functions were constructed using the maximum effect
recorded in each rat at a given dose of drug. Group means and
SEM were calculated and time-effect functions were analyzed
using two-way repeated measures ANOVA procedures followed
by Bonferroni’s posthoc test; dose-effect functions were ana-
lyzed using one-way repeated measures ANOVA procedures
followed by Dunnett’s multiple comparison t test; p was set at
<0.05, and statistical analyses were performed using GraphPad
Prism 5.03 (GraphPad Software, San Diego, CA).
Molecular Modeling. Compound 7e-β underwent torsional
sampling using the MCMM (Monte Carlo multiple minimum)
protocol39,40 in MacroModel.41The search was conducted using
the OPLS_2005 force field42 in a GB/SA water model43 with a
constant dielectric of 1.0 and an extended cutoff. An energy
window of 21.0 kJ mol-1 (5 kcal mol-1) was employed, and
redundant conformers were eliminated using a rmsd cutoff of
˚
0.5 A for all atoms.
cAMP Assay. HEK293 cells stably expressing rCB1 receptor
were used for the studies. The cAMP assay was carried out using
PerkinElmer’s Lance ultra cAMP kit following the protocol of
the manufacturer. Briefly, the assay was carried out in a 384-well
plate using 1000 cells/well. The cells were harvested with none-
nzymatic cell dissociation reagent Versene, and they were
washed once with HBSS and resuspended in the stimulation
buffer. The various concentrations of 7e-β (5 μL) in forskolin
(2 μM final concentration) containing stimulation buffer were
added to the plate followed by the cell suspension (5 μL). The
cells were stimulated for 30 min at room temperature. Then Eu-
cAMP tracer working solution (5 μL) and Ulight-anti-cAMP
working solution (5 μL) were added to the plate and incubated
at room temperature for 60 min. The plate was read on a
PerkinElmer Envision instrument. The EC50 was determined
by nonlinear regression analysis using GraphPad Prism soft-
ware (GraphPad Software, Inc., San Diego, CA).
Methods for In Vivo Behavioral Characterization of 7e-β. Sub-
jects. Female Sprague-Dawley rats (n = 5-6/group), weighing
between 200 and 350 g (Charles River, Wilmington MA), were
used. Rats were tested repeatedly with at least three days inter-
vening between drug sessions. Experiments occurred at roughly
the same time (10:00 a.m.-5:00 pm) during the light portion of
the daily light/dark cycle. Outside of experimental sessions, rats
were group housed (2/cage) in a climate controlled vivarium, and
they had unrestricted access to food and water except during the
6 h test sessions.
Procedure. Temperature was recorded using a thermistor
probe (model 401, Measurement Specialties, Inc., Dayton,
OH) inserted to a depth of 7.5 cm and secured to the tail with
micropore tape. Rats were minimally restrained and isolated in
38 cm ꢀ 50 cm ꢀ 10 cm plastic stalls. Temperature was read to
the nearest 0.01 °C using a thermometer (model 4000A, Mea-
surement Specialties, Inc.). Two baseline temperature measures
were recorded at 15 min intervals, and drugs were injected
immediately after the second baseline was recorded. After
injection, temperature was recorded every 30 min for 3 h and
every hour thereafter for a total of 6 h. The change in tempera-
ture was determined for each rat by subtracting temperature
readings from the average of the two baseline measures.
Antinociception was measured using modified version of the
tail-flick procedure of D’Amour and Smith.44 Radiant heat
from a halogen lamp was focused on the tail using a commercial
tail-flick apparatus (model LE7106, Harvard Apparatus, Hol-
liston, MA); movement of the tail activated a photocell, turning
off the lamp and a reaction timer. The lamp intensity was
adjusted to yield baseline values of 2-3 s, and a maximum
Acknowledgment. We are grateful to Pusheng Fan for the
radioligand binding assays. This work was supported by grants
from the National Institute on Drug Abuse, DA009158,
DA003801, and DA007215.
Supporting Information Available: Elemental analysis results
for compounds 5a-5e, 6a-6e, 14a-14c, 15a-15c, 16, 22, 7c-β,
1
7e-β, 23, and 24 as well as H NMR, 13C NMR, 13C DEPT,
COSY, HSQC, HMBC, and NOESY spectra of compound 5b in
CDCl3 solutions. This material is available free of charge via the
Internet at http://pubs.acs.org.
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