Probing the Cannabinoid Receptor Subsite at C1′
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 15 3227
5.44 (br s, 1H, 8-H), 4.74 (s, 1H, OH), 3.26-3.20 (m, 1H, 10R-
H), 2.8-2.6 (m, 5H), 2.18 (m, 1H, 10a-H), 1.93-1.80 (m, 7H,
2′-CH2, 6a-H, 7-CH, 10â-H, SCH2CH2), 1.70 (s, 3H, 9-CH3),
1.40 (s, 3H, 6-CH3), 1.26-1.18 (br s, 8H,-CH2-), 1.19 (s, 3H,
6-CH3), 0.82 (t, 3H, J ) 8.5 Hz, 7′-CH3); 13C NMR (CDCl3) δ
155.2, 154.9, 142.1, 134.7, 119.3, 111.8, 111.1, 107.7, 76.8, 58.8,
55.5, 45.1, 44.8, 35.9, 31.7, 31.5, 29.3, 27.8, 27.6, 25.3, 23.8,
23.5, 22.5, 18.5, 14.0; Anal. (C26H38O2S2) C, H.
2-(3,5-Dim eth oxyp h en yl)-(1,3)-d ith iola n e (13). The syn-
thesis was carried out analogous to the preparation of 11 using
12 (1.0 g, 6.0 mmol), 1,2-ethanedithiol (0.755 mL, 9.0 mmol),
and boron trifluoride etherate (0.14 mL, 1.2 mmol), in anhy-
drous CH2Cl2 (24 mL); yield: 87% (1.27 g); light yellow oil. 1H
NMR (300 MHz, CDCl3) δ 6.70 (d, J ) 2.2 Hz, 2H), 6.36 (t, J
) 2.2 Hz, 1H), 5.58 (s, 1H, 1′-H), 3.80 (s, 6H, OCH3), 3.50-
3.30 (m, 4H, -S(CH2)2S-); Anal. (C11H14O2S2) C, H.
5-(1,3-Dith iola n -2-yl)r esor cin ol (4c). The synthesis was
carried out analogous to the preparation of 4a using 13 (0.64
g, 2.64 mmol) and boron tribromide (0.56 mL, 5.81 mmol) in
anhydrous CH2Cl2 (66 mL). The reaction was completed in 48
h at -78 °C to 0 °C; yield: 87% (0.49 g); yellow gum; (lit.28
gum, no data reported). 1H NMR (300 MHz, CDCl3-CD3-
COCD3) δ 6.81 (br s, 2H, OH) 6.53 (d, J ) 2.4 Hz, 2H), 6.25 (t,
142.2, 134.7, 119.3, 112.6, 110.5, 107.5, 104.8, 104.7, 76.8, 64.4,
44.8, 40.2, 35.8, 31.7, 29.4, 27.8, 27.5, 23.5, 22.6, 18.5, 14.0;
mass spectrum m/z (relative intensity) 400 (M+, 4), 352 (3),
315 (100), 77 (27). Exact mass calculated for
400.2614; found, 400.2618. Anal. (C25H36O4) C, H.
C25H36O4;
(6a R-tr a n s)-3-[2-Hexyl-4,5-d im et h yl-(1,3)-d it h iola n -2-
yl]-6a ,7,10,10a -tetr a h yd r o-6,6,9-tr im eth yl-6H-d iben zo[b-
,d ]p yr a n -1-ol (2e). To a solution of 14 (0.050 g, 0.14 mmol)
in 1,2-dimethyl-1,2-ethanedithiol (0.086 mL, 0.70 mmol) and
triethyl orthoformate (0.024 mL, 0.14 mmol) at 0 °C was added
p-toluenesulfonic acid (0.51 mg, 0.003 mmol). Following the
addition of the acid, the reaction mixture was stirred at room
temperature for 10 h. The workup was carried out analogous
to the preparation of 2d . Yield: 60% (38.7 mg); yellow gum.
1H NMR (300 MHz, CDCl3) δ 6.72 (d, J ) 1.9 Hz, 1H, ArH,
2e2), 6.65 (d, J ) 1.9 Hz, 1H, ArH, 2e1), 6.63 (d, J ) 1.9 Hz,
1H, ArH, 2e2), 6.57 (d, J ) 1.9 Hz, 1H, ArH, 2e1), 5.43 (br s,
2H, 8-H, 2e1, 2e2), 4.75 (br s, 2H, OH, 2e1, 2e2), 3.86-3.84
(m, 2H, -SCHCHS-, 2e1), 3.55-3.45 (m, 1H, -SCHS-, 2e2),
3.35-3.30 (m, 1H, -SCHS-, 2e2), 3.29-3.16 (m, 2H, 10R-H, 2e1,
2e2), 2.78-2.67 (m, 2H, 10a-H, 2e1, 2e2), 2.31-2.10 (m, 6H,
7-CH, 2′-CH2-, 2e1, 2e2), 1.92-1.75 (m, 6H, 6a-H, 7-CH, 10â-
H, 2e1, 2e2), 1.70 (s, 6H, 9-CH3, 2e1, 2e2), 1.40 (s, 6H, 6-CH3,
2e1, 2e2), 1.38-1.25 (m, 12H, -SC(CH3)-, 2e1, 2e2), 1.21 (br s,
16H,-CH2-, 2e1, 2e2), 1.10 (s, 6H, 6-CH3, 2e1, 2e2), 0.83 (t, 6H,
J ) 6.9 Hz, 7′-CH3, 2e1, 2e2); 13C NMR (CDCl3) δ 157.7, 154.3,
144.3, 134.7, 119.3, 112.3, 108.8, 106.2, 76.6, 72.8, 56.7, 55.7,
53.7, 48.8, 47.5, 44.7, 35.8, 31.6, 29.7, 27.8, 27.5, 27.2, 26.8,
23.5, 22.6, 18.5, 14.1; mass spectrum m/z (relative intensity)
460 (M+, 5), 446 (10), 404 (6), 375 (100). Exact mass calculated
for C27H40O2S2; 460.2470; found, 460.2464. Anal. (C27H40O2S2)
C, H.
J
) 2.4 Hz, 1H), 5.45 (s, 1H, 1′-H), 3.43-3.21 (m, 4H,
-S(CH2)2S-); 13C NMR (CDCl3-CD3COCD3) δ 157.5, 142.8,
106.8, 102.5, 55.9, 93.8, 10.0; Anal. (C9H10O2S2) C, H.
(-)-2-[3-3,4-tr a n s-p -Men th a d ien -(1,8)-yl]-5-(1,3-d ith i-
ola n -2-yl)r esor cin ol (3c). The synthesis was carried out
analogous to the preparation of 3a using 4c (0.440 g, 2.52
mmol), (+)-cis/ trans-p-mentha-2,8-dien-1-ol (0.390 g, 2.56
mmol), and p-toluenesulfonic acid (0.073 g, 0.38 mmol) in
anhydrous benzene (19 mL); yield: 30% (0.21 g); yellow viscous
oil. 1H NMR (300 MHz, CDCl3) δ 6.55 (br s, 2H), 5.53 (br s,
1H, 2-H), 5.48 (s, 1H, 1′-H), 4.64 (s, 1H, >CdCH2), 4.54 (s,
1H, >CdCH2), 3.85 (m, 1H, 3-H), 3.50-3.27 (m, 4H, -S(CH2)2S-
), 2.4 (m, 1H), 2.30-2.11 (m, 2H), 1.8 (br s, 5H), 1.65 (s, 3H,
10-CH3); Anal. (C19H24O2S2) C, H.
(6a R-tr a n s)-3-(1,3-Dith iola n -2-yl)-6a ,7,10,10a -tetr a h y-
d r o-6,6,9-tr im eth yl-6H-d iben zo[b,d ]p yr a n -1-ol (2c). The
synthesis was carried out analogous to the preparation of 2a
using 3c (0.20 g, 0.574 mmol) and boron trifluoride etherate
(0.26 mL, 2.05 mmol) in anhydrous CH2Cl2 (16.4 mL); yield:
50% (0.10 g); yellow solid. mp 56-59 °C (lit.28 no data
reported); 1H NMR (300 MHz, CDCl3) δ 6.59 (s, 1H, ArH), 6.46
(s, 1H, ArH), 5.47 (s, 1H, 8-H), 5.41 (s, 1H, 1′-H), 4.96 (br s,
1H, OH), 3.46-3.28 (m, 4H, -S(CH2)2S-), 3.25-3.13 (m, 1H,
10R-H), 2.72-2.60 (m, 1H, 10a-H), 2.14-1.72 (m, 4H, 6R-H,
7-CH2-, 10â-H), 1.70 (s, 3H, CH3) 1.35 (s, 3H, CH3), 1.07 (s,
3H, CH3); 13C NMR (CDCl3) δ 155.1, 154.9, 140.1, 134.7, 119.3,
113.1, 110.0, 106.5, 76.6, 55.7, 44.8, 40.1, 35.8, 31.7, 30.0, 27.8,
27.5, 23.5, 18.5; mass spectrum m/z (relative intensity) 348
(M+, 100), 333 (10), 305 (24), 289 (60), 265 (76), 105 (29). Exact
mass calculated for C19H24O2S2; 348.1218; found, 348.1221.
Anal. (C19H24O2S2) C, H.
(6a R-tr a n s)-3-[2-Hexylben zo(1,3)d ith iol-2-yl]-6a ,7,10,-
10a -tetr a h yd r o-6,6,9-tr im eth yl-6H-d iben zo[b,d ]p yr a n -1-
ol (2f). The title compound was prepared from 14 (0.10 g, 0.28
mmol), in anhydrous CH2Cl2 (1.12 mL), 1,2-benzenedithiol
(0.06 mL, 0.5 mmol) and boron trifluoride etherate (0.01 mL,
0.084 mmol), following the procedure described for compound
11. Purification by flash column chromatography (20% diethyl
ether-petroleum ether as eluent) gave 47.2 mg (35%) of 2f as
1
white foam. mp 57-60 °C dec; H NMR (300 MHz, CDCl3) δ
7.18-7.14 (m, 2H), 7.00-6.97 (m, 2H), 6.66 (d, J ) 1.9 Hz,
1H, 4-H), 6.60 (d, J ) 1.9 Hz, 1H, 2-H), 5.43 (d, J ) 3.7 Hz,
1H, 8-H), 4.90 (s, 1H, OH), 3.20-3.14 (dd, J ) 20 Hz, J ) 4
Hz, 1H, 10R-H), 2.70 (m, 1H, 10a-H), 2.41-2.39 (m, 2H, 2′-
CH2-), 2.36-2.12 (m, 1H, 7-H), 1.92-1.77 (m, 3H), 1.69 (s, 3H,
9-CH3), 1.40 (s, 3H, 6-CH3), 1.30-1.10 (m, 8H, -CH2-), 1.09 (s,
3H, 6-CH3), 0.80 (t, J ) 6.5 Hz, 3H, 7′-CH3); 13C NMR (CDCl3)
δ 154.9, 154.6, 141.6, 138.1, 134.6, 125.4, 122.3, 119.3, 112.7,
108.7, 106.5, 76.6, 74.8 (1′-C), 44.7, 44.5, 35.7, 31.6, 29.1, 27.8,
27.5, 26.2, 23.4, 22.5, 18.5, 14.0; mass spectrum m/z (relative
intensity) 480 (M+, 4), 446 (8), 395 (100). Exact mass calculated
for C29H36O2S2; 480.2157; found, 480.2154. Anal. (C29H36O2S2)
C, H.
(6a R-tr a n s)-3-[2-Hexyl-(1,3)-d ioxola n -2-yl]-6a ,7,10,10a -
tetr ah ydr o-6,6,9-tr im eth yl-6H-diben zo[b,d]pyr an -1-ol (2d).
To a solution of 14 (0.031 g, 0.087 mmol) in ethylene glycol
(0.051 mL, 0.932 mmol) and triethyl orthoformate (0.014 mL,
0.087 mmol) at 0 °C was added p-toluenesulfonic acid (0.31
mg, 0.002 mmol). The reaction mixture was stirred at that
temperature for 24 h, and at completion a saturated solution
of NaHCO3 was added. The mixture was extracted with diethyl
ether and the organic layer washed with water and brine and
dried over Na2SO4. Solvent evaporation and purification by
flash column chromatography on silica gel (30% diethyl ether-
petroleum ether) afforded 31.4 mg (90% yield) of the title
Ra d ioliga n d Bin d in g Assa y. Forebrain synaptosomal
membranes were prepared from frozen rat brains by the
method of Dodd et. Al.42 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 proce-
dure.35 The displacement of specifically tritiated CP-55,940
from these membranes was used to determine 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. Radio-
activity 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-
1
compound 2d as a yellow gum. H NMR (300 MHz, CDCl3) δ
6.50 (d, J ) 1.2 Hz, 1H, 4-H), 6.42 (d, J ) 1.2 Hz, 1H, 2-H),
5.49 (br s, 1H, OH), 5.41 (br s, 1H, 8-H), 3.97 (m, 2H, -O(CH2)-
), 3.80 (m, 2H, -O(CH2)-), 3.29-3.18 (m, 1H, 10R-H), 2.75-
2.65 (m, 1H, 10a-H), 2.15-2.10 (m, 1H, 7R-H), 1.91-1.80 (m,
5H, 6R-H, 7â-H, 10â-H, 2′-CH2-), 1.70 (s, 3H, 9-CH3), 1.40 (s,
3H, 6-CH3), 1.20 (br s, 8H,-CH2-), 1.10 (s, 3H, 6-CH3), 0.82 (t,
3H, J ) 6.1 Hz, 7′-CH3); 13C NMR (CDCl3) δ 155.0, 154.8,