Probes for narcotic receptor mediated phenomena 49. N-substituted rac-cis-4a-arylalkyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c[pyridin-6-ols

Article abstract of DOI:10.1016/j.ejmech.2015.01.025

Racemic N-substituted-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ols containing cis-4a-aralkyl groups were explored as probes for opioid receptors. Specifically cis-4a-phenylpropyl,-phenylbutyl, and-phenylpentyl groups coupled with widely varied substituents on the nitrogen atom were synthesized and their pharmacological profiles at opioid receptors examined. The study yielded compounds with good affinity and moderate to potent antagonist activity at the μ and δ-opioid receptors, and agonist activity at the k °-opioid receptor. An N-allyl substituent in the C4a phenylpropyl series induced 6-fold higher affinity at δ-than μ-receptors, while an N-CPM substituent in the C4a (CH₂)₃Ph series led to a compound with high δ-affinity and potent δ-antagonist activity.

Full text of DOI:10.1016/j.ejmech.2015.01.025

European Journal of Medicinal Chemistry 92 (2015) 531e539
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Probes for narcotic receptor mediated phenomena 49. N-substituted
rac-cis-4a-arylalkyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-
6-ols
,
, b
Malliga R. Iyer a b, Richard B. Rothman c, Christina M. Dersch c, Arthur E. Jacobson a
,
Kenner C. Rice a
, b, *
a Drug Design and Synthesis Section, Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse,
National Institutes of Health, Department of Health and Human Services, 9800 Medical Center Drive, Bethesda, MD 20892-3373, USA
b Intramural Research Program, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Department of Health and Human
Services, 9800 Medical Center Drive, Bethesda, MD 20892-3373, USA
c Medicinal Chemistry Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and
Human Services, Baltimore, MD 21224, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Racemic N-substituted -1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ols containing cis-4a-aralkyl
groups were explored as probes for opioid receptors. Specifically cis-4a-phenylpropyl, -phenylbutyl, and-
phenylpentyl groups coupled with widely varied substituents on the nitrogen atom were synthesized
and their pharmacological profiles at opioid receptors examined. The study yielded compounds with
Received 22 October 2014
Received in revised form
24 December 2014
Accepted 12 January 2015
Available online 13 January 2015
good affinity and moderate to potent antagonist activity at the
activity at the -opioid receptor. An N-allyl substituent in the C4a phenylpropyl series induced 6-fold
higher affinity at -than -receptors, while an N-CPM substituent in the C4a (CH2)3Ph series led to a
compound with high -affinity and potent -antagonist activity.
m- and d-opioid receptors, and agonist
k
d
m
Keywords:
Synthesis
d
d
Published by Elsevier Masson SAS.
cis-4a-arylalkyl-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ols
Opioid receptors
[
m
35S]GTP-
-and
g
-S efficacy assays
d-receptor antagonists
1. Introduction
that are frequently observed with the use of opioid analgesics
[5e7]. It has also been noted that a -agonist can counteract the
respiratory depression induced by -agonists without interfering
with antinociceptive activity [8]. We have prepared derivatives of
the cis-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ols to see
d
From our work [1e3] and that of Hutchison et al. [4] it has been
shown that cis-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-
ols (1, Fig. 1), when suitably substituted on the tertiary nitrogen
m
and the C4a-position, have high or moderate affinity for either
m
-,
d
-
if we could find new, interesting
interact with both receptors.
d-ligands, or compounds that
and -opioid receptors, and sometimes at a combination of these
k
m & d
receptors [4]. In principle, then, substituent modifications at these
positions could lead to compounds that interact with a desirable
Benzofuro[2,3-c]pyridinols can be viewed as truncated para-
d oxide-bridged phenylmorphans (2, Fig. 1, rac-(3R,6aS,11aR)-2-
methyl-1,3,4,5,6,11a-hexahydro-2H-3,6a-methanobenzofuro[2,3-c]
azocin-8-ol). In the para-d series, neither the N-methyl nor the N-
phenethyl-substituted isomer appreciably interacted with opioid
receptors [9e11]. The C4a group in its abridged form, however, gives
the benzofuropyridinols a partial flexibility, hopefully enabling the
interaction of these C4a-arylalkyl substituted benzofuro[2,3-c]pyr-
idinols with suitable amino acids in the opioid receptors that could
not be reached with the inflexible, rigid, para-d oxide-bridged
phenylmorphans. In other hexahydrobenzofuro[2,3-c]pyridin-6-
ols this flexibility was shown to allow a conformational overlap
combination of
m- and
d-opioid receptor affinity. It has been found
that compounds that combine both
m
-agonist and -antagonist
d
behavior can minimize at least some of the undesired side-effects
Abbreviations: CPM, cyclopropylmethyl; Ph, phenyl; BSA, bovine serum albu-
min; DTT, dithiothreitol; EDTA, ethylenediaminetetraacetic acid.
* Corresponding author. Drug Design and Synthesis Section, Molecular Targets
and Medications Discovery Branch, Intramural Research Program, National Institute
on Drug Abuse, National Institutes of Health, Department of Health and Human
Services, 9800 Medical Center Drive, Bethesda, MD 20892-3373, USA.
E-mail address: kennerr@mail.nih.gov (K.C. Rice).
http://dx.doi.org/10.1016/j.ejmech.2015.01.025
0223-5234/Published by Elsevier Masson SAS.

532
M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
ol (10d) was the most selective ligand for the -receptor among
all of the new compounds. It was found to be a -antagonist in the
functional [35S]GTP-
-S assay and had no - or k-agonist activity,
d
d
g
m
but was not very efficacious (Ke ¼ 103 nM).
Five of the compounds synthesized with a C4a-phenylbutyl
substituent (Table 1, 11ae11i), those combined with a phenethyl
(11a),
fluromethyphenethyl (11e), and cyclopropylmethyl (11f) substitu-
ent on nitrogen were found to have good affinity for the -receptor,
with Ki's ranging between 4 and 14 nM. Four of those compounds
were found to interact well with the -receptor, with Ki's between 7
and 21 nM (11a, 11b, 11e and 11f), and one had high affinity and
moderate selectivity for the
-receptor (11f, Ki ¼ 1.6 nM). Most
notably, 2-phenethyl-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-ol (11a) showed good and equal af-
finity for both - and
-receptors (Ki ¼ 7 nM), coupled with only a
little affinity (Ki > 100 nM) for the -receptor ( or > 15).
Compounds in the C4a-phenylpentyl series (Table 1, 12ae12f)
were found to have the highest affinity for the -receptor. Five of
a
p- or o-fluorophenethyl (11b, 11c), the p-tri-
m
d
Fig. 1. General structure of benzofuro[2,3-c]pyridinols and para-d oxide bridged
phenylmorphans.
k
that resembles morphine more than the oxide-bridged phenyl-
morphans [2]. For these reasons we concentrated on the synthesis
and pharmacological evaluation of the C4a-phenylpropyl, -phenyl-
butyl and -phenylpentyl substituents combined with a variety of N-
substituents. These compounds were obtained using our previous
discovery of a simpler route for the synthesis of C4a-substituted
hexahydrobenzofuro[2,3-c]pyridin-6-ols that has enabled us to
study compounds with a variety of substituents in the C4a-position
as well as on the piperidine nitrogen atom [1,3,12].
m
d
k
m
d/k
m
the 6 compounds, all but 12f, had single-digit Ki's, between 3 and
6 nM (compounds with an N-phenethyl (12a), a p- or o-fluo-
rophenethyl (12b, 12c), the p-trifluromethyphenethyl (12d), and
cyclopropylmethyl (12e). These were the same N-substituents
found to have good affinity in the C4a-phenylbutyl series e but in
2. Results and discussion
the C4a-phenylpentyl series they had even higher affinity for the
receptor. However, none of the C4a-phenylpentyl compounds had
appreciable -receptor affinity, all Ki's were found to be >20 nM.
m-
2.1. Chemistry
d
The N-cyclopropylmethyl (12e) compound also had high
affinity (Ki ¼ 3.7 nM).
k-receptor
We synthesized compounds 7ae7c with a C4a-phenylpropyl,
phenylbutyl and phenylpentyl group as the arylalkyl groups from
2.3. Efficacy of selected compounds ([35S]GTP-
g-S assay)
4-(2,5-dimethoxyphenyl)-1-methyl-1,2,3,6-tetrahydropyridine
3
(Scheme 1), using established procedures [12]. The N-position was
subjected to different variations in these compounds. Further
modification was achieved first by initial acetate protection of the
N-methyl phenolic compounds 7ae7c to give 8ae8c [12].
Sequential treatment of 8ae8c with Troc-Cl, deprotection of the
acetate, and Zn-dust mediated removal of the Troc group gave the
N-nor compounds 9ae9c. Compounds 9ae9c was N-alkylated to
give compounds 10e12 (Scheme 1) that included the N-cyclo-
Among the C4a-phenylpropyl compounds, only two showed
moderate to good efficacy as - and -receptor antagonists
(Table 2), the N-allyl compound, 10f, and the N-cyclopropylmethyl
compound 10g. The N-allyl substituted compound 10f was more
m
d
efficacious at the
respectively), and had perhaps 3-fold
had a small amount of undesired agonist activity at the
(Table 2). -Receptor agonist activity has been known to induce
dysphoric effects in humans [13]. The N-cyclopropylmethyl com-
pound 10g had considerably greater activity as - and -receptor
antagonists than 10f (Ke at - and
¼ 9 and 4 nM, respectively).
Although the selectivity was similar to that in 10f, it showed an
ED50 ¼ 32 nM (Emax ¼ 91) as a -agonist.
Of those examined in the C4a-phenylbutyl series only the N-
cyclopropylmethyl compound 11f had moderate efficacy as a
antagonist (Ke 23 nM), less efficacy as -antagonist
, but as a
d-than the
m
-receptor (Ke ¼ 14 and 47 nM,
selectivity. The compound
-receptor
m/k
k
propylmethyl,
N-allyl,
N-phenalkyl,
and
fluoro-
and
k
trifluoromethyl-substituted N-phenethyl substituents.
m
d
2.2. Opioid receptor affinity
m
d
m/k
Among the compounds with the shortest aralkyl chain at C4a, in
the C4a-phenylpropyl series (Table 1, 10ae10i), three compounds
with the least bulky moieties on nitrogen had the highest affinity
k
m-
for the
m
-receptor, the phenethyl (10a), o-flurophenylethyl (10c)
¼
a d
and cyclopropylmethyl (10g) (Ki ¼ 14, 17 and 13 nM, respectively).
(Ke ¼ 64 nM), and was about equally efficacious at
k
k-
Remarkably, seven of the 9 compounds in this C4a-substituted
agonist (ED50 ¼ 35 nM (Emax ¼ 83%). The N-cyclopropyl compound
series had good to excellent affinity for the d-receptor. All except
12e had similar activity to 11f. It's efficacy was moderate (Ke ¼ 21
10h and 10i were found to have Ki < 20 nM, and four of them had
single-digit nanomolar affinity (10a, 10d, 10f, and 10g, Ki ¼ 6.9, 7.1,
9.1, and 5.5 nM, respectively). Several 4a-substituted 1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ols have been found that
and 35 nM) as an antagonist at m- and d, and showed the highest
activity at
the substituent at C4a, the N-cyclopropylmethyl compounds were
all -agonists, no -antagonist was found.
k
as an agonist (ED50 ¼ 13 nM (Emax ¼ 70%). Regardless of
k
k
interact with d-receptors (Table 1). The combination of the mod-
erate bulk at C4a combined with N-aralkyl (10a and 10d), N-p- and
o-fluorophenethyl-substituted (10b, 10c and 10e (the p-tri-
fluromethyphenethyl compound)), or N-allyl (10f) moieties, and,
especially, with N-cyclopropylmethyl-substitution, appeared to
have enabled at least some interaction with suitable amino acids in
2.4. Conclusion
We evaluated the effect of different C4a substituents and varied
the substituent at the N-position of the benzofuropyridin-6-ol se-
ries of compounds. We obtained
d
-antagonists with high or mod-
the
moiety, at both C4a and on the nitrogen atom (10d), the
tivity was greatest 10, 12). Thus, 2,4a-bis(3-
phenylpropyl)-1,2,3,4,4a, 9a-hexahydrobenzofuro[2,3-c]pyridin-6-
d
-receptor. With the moderately bulky group, the phenylpropyl
erate efficacy (10f, 10g, and 12e), and these also had m
activity. Efforts are underway to further modify the promising
compounds through optical resolution of these racemic com-
-antagonist
d-selec-
(m/
d
>
m/k >
pounds, attempting to remove k-agonist activity that exists in the

M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
533
R1 = (CH2)3Ph
R1 = (CH2)4Ph
R1 = (CH2)5Ph
10a: R2 = (CH2)2Ph
10b: R2 = p-F(CH2)2Ph
11a: R2 = (CH2)2Ph
11b: R2 = p-F(CH2)2Ph
12a: R2 = (CH2)2Ph
12b: R2 = p-F(CH2)2Ph
10c: R2 = o-F(CH2)2Ph
10d: R2 = (CH2)3Ph
11c: R2 = o-F(CH2)2Ph
11d: R2= (CH2)3Ph
12c: R2 = o-F(CH2)2Ph
12d: R2 = p-CF3(CH2)2Ph
10e: R2 = p-CF3(CH2)2Ph
10f: R2 = CH2CH=CH2
10g: R2 = CPM
11e: R2 = p-CF3(CH2)2Ph
11f: R2 = CPM
12e: R2 = CPM
12f: R2 = o-CF3(CH2)2Ph
11g: R2 = o-CF3(CH2)2Ph
11h: R2 = (CH2)4Ph
10h: R2 = o-CF3(CH2)2Ph
10i: R2 = m-CF3(CH2)2Ph
11i: R2 = m-CF3(CH2)2Ph
Scheme 1. Reagents and conditions [12]: (a) n-BuLi, Br(CH2)n-Ph (where n ¼ 3, 4, or 5), ꢀ78 ꢁC to rt; (b) (i) NBS, ꢀ78 ꢁC to rt, (ii) NaBH3CN, 0 ꢁC; (c) HBr, reflux; (d) Et3N, sealed
tube, 100 ꢁC; (e) Ac2O, reflux; (f) (i) proton sponge,Troc-Cl, (ii) K2CO3, MeOH, (iii) Zn, AcOH; (g) (i) R2Br, DMF, NaHCO3, 50 ꢁC, (ii) K2CO3, MeOH.
efficacious compounds by modifying the N-substituent, and
examining as yet untried moieties at the C4a position. The results
from that study will be reported in due course.
containing 1% NH4OH or gradients of EtOAc: n-hexane. Visualization
was accomplished under UV light or by staining in an iodine
chamber. Flash column chromatography was performed with Flu-
kasilica gel 60 (mesh 220e400). Atlantic Microlabs, Inc., Norcross,
GA, or Micro-Analysis, Inc., Wilmington, DE, performed elemental
analyses, and the results were within 0.4% of the theoretical values.
3. Experimental
3.1. Chemistry
3.1.1. Method A: general procedure [12] to synthesize acetate 8ae8c
Compound 7 (1.0 equiv) was treated with acetic anhydride (5.0
equiv) and heated to reflux. After completion of the reaction the
acetic anhydride was evaporated off to give a sticky solid. This solid
was applied to a silica-gel column and the desired product was
eluted using 75% EtOAc in hexanes to give a sticky brown solid
8ae8c.
Melting points were determined on a Buchi B-545 instrument
and are uncorrected. Proton and carbon nuclear magnetic resonance
(1H and 13C NMR) spectra were recorded in CDCl3 with tetrame-
thylsilane (TMS) as the internal standard on a Varian Gemini-300
spectrometer and a Bruker DMX500 wide-bore spectrometer
((proton frequency 500.13 MHz) running XWINNMR v3.1, carbon
125.757) in CDCl3 (unless otherwise noted) with the values given in
ppm (TMS as internal standard) and J (Hz) assignments of 1H reso-
nance coupling. Mass spectra (HRMS) were recorded on a VG 7070E
spectrometer or a JEOL SX102a mass spectrometer. Thin layer
chromatography (TLC) analyses were carried out on Analtech silica
gel GHLF 0.25 mm plates using various gradients of CHCl3/MeOH
3.1.1.1. 2-Methyl-4a-(4-phenylpropyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-yl acetate (8a). Using Method A, 7a
[12] (7.5 g, 22 mmol) gave 8a (7.4 g, 87%) as a sticky solid. 1H NMR
(500 MHz, CDCl3)
1H), 7.12 (d, J ¼ 7.3 Hz, 2H), 6.83 (d, J ¼ 2.3 Hz, 1H), 6.77 (d,
d
7.26 (dd, J ¼ 9.1, 5.6 Hz, 2H), 7.18 (d, J ¼ 7.2 Hz,

534
M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
Table 1
Table 2
Opioid receptor binding affinities of compounds in the C4a-phenylpropyl, -phe-
nylbutyl, and -phenypentyl series.
Antagonist (Ke SD, nM) and agonist (ED50 SD, nM, and Emax SD) activities from
[
35S]GTP-
g
-S functional assays.
Cmpd
Ki SD (nM)
ma db
Compd
Antagonist activity
Agonist Activity
kc
MOR Ke
(nM)
DOR Ke
(nM)
MOR ED50 KOR ED50
(Emax)a
(Emax)a
R1 ¼ (CH2)3Ph R2
¼
10a
10b
10c
10d
CH2CH2Ph
14
1
2
2
5
6.9 0.4 110
6
9
R1 ¼ (CH2)3Ph R2
p-F-CH2CH2Ph
o-F-CH2CH2Ph
CH2 CH2CH2
CH2CH2CH2Ph
p-CF3CH2CH2Ph
CH2CH]CH2
CPM
47
17
73
15
2
110
10a
10b
10c
CH2CH2Ph
e
192 18
176 19
492 53
560 120
(73 4)
I
I
I
I
13 0.7 160 10
7.1 0.9 88
6
p-F-
CH2CH2Ph
o-F-
518 83
10e
10f
10g
10h
10i
27 0.2
18
9.1
5.5
2
1
1
139 12
5.1 0.2
1.4 0.1
795 43
923 58
e
854 164
53
13
3
1
CH2CH2Ph
(79 4)
10d
10e
CH2CH2CH2Ph 1301 257 103 14
I
I
I
I
o-CF3CH2CH2Ph
m-CF3CH2CH2Ph
351 26
93
229 22
116 18
p-
359 82
437 43
8
CF3CH2CH2Ph
10f
CH2CH]CH2 47
6
14
4
3
I
I
137 26
(83 3)
R1 ¼ (CH2)4Ph R2
¼
10g
CPM
9
0.82
0.64
32
5
11a
11b
11c
11d
11e
11f
11g
11h
11i
CH2CH2Ph
7.7 0.5
7.3 0.5 117 13
(91 2)
p-F-CH2CH2Ph
o-F-CH2CH2Ph
CH2CH2CH2Ph
p-CF3CH2CH2Ph
CPM
o-CF3CH2CH2Ph
(CH2)4Ph
m-CF3CH2CH2Ph
12
10.1
80
1
1
3
21
26
57
21
16
3
4
4
4
3
147 19
230 30
424 41
163 16
1.6 0.1
¼
3.8 0.6
14 0.5
294 21
pid
CH2CH2Ph
e
2747 229 542 125
(77 4)
I
589 61 1769 129
68 410 36
148 19 3184 482
e
675 95
1166 278 I
(52 3)
6
38
3
e
2779 388 1008 180 I
(84 4)
23
2
64
6
I
35
(83 2)
I
4
R1 ¼ (CH2)5Ph R2
¼
12a
12b
12c
12d
12e
12f
CH2CH2Ph
5.6 0.8
4.2 0.5
5.8 0.6
3.1 0.4
3.9 0.8
159 16
25
44
54
127 12
24
4
5
3
82
130
177 11
297 12
3.7 0.2
4
7
410 45
595 90
I
p-F-CH2CH2Ph
o-F-CH2CH2Ph
p-CF3CH2CH2Ph
CPM
CF3CH2CH2Ph
2
R1 ¼ (CH2)5Ph R2 ¼
o-CF3CH2CH2Ph
719 36 1119 63
12a
12b
12c
12e
CH2CH2Ph
e
e
e
836 94
1077 156 I
103
1208 185 929 125
109
1032 134 I
4
p-F-
CH2CH2Ph
o-F-
CH2CH2Ph
CPM
I
Morphine
DAMGO
U69,593
2.6 0.01 605 36
1.2 0.1 1500 170 e
299 49
3.5 0.3
4
I
>2
m
M
>12 mM
107
I
4
Opiate receptor binding assays were performed using CHO hMOR, CHO hDOR and
CHO hKOR cells. The data of three experiments were pooled (N ¼ 30 data points)
and fit to the two-parameter logistic equation for the best-fit estimates ( SD) of the
IC50, the value of which was then used to calculate the Ki value, as described in
section 3.1.4; Ph ¼ phenyl; CPM ¼ cyclopropylmethyl.
21
2
35
7
13
3
(70 3)
Naloxone
(e)-U50,488
2.3 0.3
e
e
27
3
All data are n equal or greater than 3.
(99 2)
a
[3H]-DAMGO.
b
[3H]-DADLE.
None of the compounds tested had KOR antagonist activity or DOR agonist activity;
c
[3H]-U69,593.
Ph ¼ phenyl, CPM ¼ cyclopropylmethyl; I ¼ inactive (ED50 > 1500); e ¼ not tested.
d
a
Partial inhibitor (compound 11h appeared to show some inverse agonist
Emax ¼ the percent the compound stimulated GTP-
g-S binding as compared to
activity).
the stimulation produced by 1000 nM DAMGO, 500 nM SNC80 or 500 nM
(e)-U50,488 (when the % stimulation is considerably less than 100%, the compound
is said to be a partial agonist).
J ¼ 8.5 Hz, 1H), 6.72 (d, J ¼ 2.2 Hz, 1H), 4.48 (t, J ¼ 6.0 Hz, 1H), 2.75
(dd, J ¼ 12.2, 5.2 Hz, 1H), 2.54 (q, J ¼ 8.1 Hz, 2H), 2.38 (dq, J ¼ 17.2,
5.9 Hz, 2H), 2.28 (s, 3H), 2.25 (s, 3H), 2.16e2.11 (m, 1H), 2.00 (td,
J ¼ 7.0, 3.6 Hz, 1H), 1.79e1.70 (m, 2H), 1.58e1.55 (m, 3H). 13C NMR
J ¼ 12.2, 5.2 Hz, 1H), 2.56 (t, J ¼ 7.7 Hz, 2H), 2.37 (ddd, J ¼ 18.1, 12.0,
6.3 Hz, 2H), 2.28 (s, 3H), 2.25 (s, 3H), 2.16e2.12 (m, 2H), 2.00 (ddd,
J ¼ 14.2, 6.1, 3.5 Hz, 2H), 1.82e1.77 (m, 1H), 1.69 (dt, J ¼ 10.7, 5.3 Hz,
(126 MHz, CDCl3)
d 169.9, 156.4, 144.6, 142.0, 135.0, 128.5, 128.4,
2H), 1.57 (dt, J ¼ 15.7, 7.9 Hz, 2H), 1.29 (dd, J ¼ 18.4, 11.3 Hz, 4H). 13
C
125.9, 121.0, 116.7, 110.8, 85.4, 56.4, 51.8, 46.3, 46.2, 45.6, 38.8, 36.3,
33.0, 25.8, 21.32, 21.22. HRMS (TOF MS ESþ) calcd for C23H28NO3
(MþH)þ 366.2069, found: 366.2061.
NMR (126 MHz, CDCl3):
d 170.0, 156.4, 144.6, 142.6, 135.2, 128.5,
128.4, 128.4, 125.8, 120.9, 116.6, 110.8, 85.4, 56.5, 51.9, 46.4, 45.7,
39.0, 35.8, 33.1, 32.1, 23.7, 21.3. HRMS (TOF MS ESþ) calcd for
C
24H30NO3 (MþH)þ: 380.2226; found: 380.2237.
3.1.1.2. 2-Methyl-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-yl acetate (8b). Using Method A, 2.2 g
of 7b [12] gave 2.2 g 8b (89%). 1H NMR (500 MHz, CDCl3):
3.1.1.3. 2-Methyl-4a-(5-phenylpentyl)-1,2,3,4,4a,9a-hexahy-
d
7.26e7.24 (m, 2H), 7.14 (dd, J ¼ 23.1, 7.1 Hz, 2H), 6.84 (dd, J ¼ 8.5,
drobenzofuro[2,3-c]pyridin-6-yl acetate (8c). Using Method A, 5.0 g
2.3 Hz, 2H), 6.78e6.76 (m, 2H), 4.47 (t, J ¼ 6.0 Hz, 1H), 2.74 (dd,
of 7c [12] gave 5.18 g of 8c (91%). 1H NMR (500 MHz, CDCl3):
d 7.28

M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
535
(s, 1H), 7.25 (s, 1H), 7.18e7.13 (m, 3H), 6.83 (dd, J ¼ 8.5, 2.2 Hz, 1H),
3.1.3. Method C: general procedure for synthesis of compounds
10e12
6.78e6.75 (m, 2H), 4.47 (t, J ¼ 5.8 Hz, 1H), 2.72 (dd, J ¼ 12.2, 5.0 Hz,
1H), 2.54 (t, J ¼ 7.6 Hz, 2H), 2.38 (t, J ¼ 6.1 Hz, 2H), 2.28 (s, 3H), 2.25
(s, 3H), 2.17e2.13 (m, 2H), 1.99 (ddd, J ¼ 13.9, 6.0, 3.1 Hz, 1H), 1.85 (t,
J ¼ 3.1 Hz, 3H), 1.77 (td, J ¼ 9.1, 4.6 Hz, 2H), 1.64 (dd, J ¼ 7.6, 4.8 Hz,
A mixture of the amine 9, alkyl bromide (1.2 equiv) and NaHCO3
(2 equiv) in DMF (20 mL) was heated at 50 ꢁC for 20 h. After cooling
to room temperature, the reaction mixture was poured into ice-
H2O, and the product was extracted with Et2O. The ethereal ex-
tracts were washed with saturated NH4Cl solution, dried over
Na2SO4, and the solvent was removed in vacuo to afford an oil. The
crude oil was subjected to flash chromatography on silica gel using
75% EtOAc in hexanes as the eluent to give the 10e12 as solids.
1H),1.58e1.53 (m,1H),1.53e1.48 (m,1H),1.25 (d, J ¼ 3.5 Hz, 2H). 13
C
NMR (126 MHz, CDCl3):
d 170.0, 155.1, 145.3, 142.4, 128.4, 128.23,
125.6, 122.5, 117.2, 117.1, 112.9, 111.4, 82.0, 51.5, 50.1, 44.4, 39.5, 35.8,
31.3, 29.3, 29.0, 23.4, 23.3, 21.2. HRMS (TOF MS ESþ) calcd for
C
25H32NO3 (MþH)þ: 394.2382; found: 394.2375.
3.1.2. Method B: general procedure for synthesis of compounds
9ae9c
3.1.3.1. 4a-(3-Phenylpropyl)-2-(phenethyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-ol (10a). Using Method C, 500 mg of
9a gave 220 mg compound 10a (33%). Mp 179e180 ꢁC; 1H NMR
To compound 8 (1.0 equiv) in DCE was added Troc-Cl (1.2 equiv)
and proton-sponge (1.2 equiv) and stirred overnight for 12 h. The
reaction mixture was then washed with 1 N HCl and the mixture
was extracted with ethyl acetate. The aqueous layer was washed
twice with ethyl acetate and the combined organic extracts were
evaporated to give a brown oil. The crude oil was triturated with
hexanes and treated with K2CO3 in methanol and stirred for 4 h.
After completion of the reaction, as indicated by TLC, the mixture
was extracted with chloroform, dried over sodium sulfate and used
without purification in the next step. The crude oil was taken up in
AcOH (7.0 mL) and Zn powder (1.2 eq) was added to it slowly with
vigorous stirring. After the reaction was complete (as determined
by TLC), the reaction mixture was filtered though a plug of cotton
and the cotton was washed with CH2Cl2. Ammonium hydroxide
(10.0 mL) was slowly added to the organic solution followed by
extraction of the mixture with CH2Cl2. Evaporation of the organic
layer followed by trituration of the crude oil with 2-propanol gave
9ae9c as a sticky brown solid.
(500 MHz, CDCl3):
d
7.27e7.24 (m, 5H), 7.15 (td, J ¼ 16.6, 7.3 Hz, 5H),
6.66 (d, J ¼ 8.4 Hz, 1H), 6.58 (dd, J ¼ 8.4, 2.5 Hz, 1H), 6.51 (d,
J ¼ 2.4 Hz, 1H), 4.47 (t, J ¼ 6.2 Hz, 1H), 2.95e2.92 (m, 1H), 2.78 (t,
J ¼ 8.1 Hz, 2H), 2.55 (dt, J ¼ 13.8, 6.7 Hz, 4H), 2.37 (dd, J ¼ 11.6,
7.2 Hz, 1H), 2.21 (t, J ¼ 9.3 Hz, 1H), 2.03 (dt, J ¼ 14.4, 2.7 Hz, 1H),
1.82e1.80 (m, 1H), 1.72 (dd, J ¼ 13.1, 9.9 Hz, 2H), 1.57 (q, J ¼ 10.6 Hz,
2H). 13C NMR (126 MHz, CDCl3):
d 152.9, 150.1, 142.2, 140.3, 134.9,
128.5, 128.4, 126.2, 126.0, 114.6, 113.6, 113.1, 110.9, 110.8, 85.0, 60.6,
54.6, 49.9, 46.4, 39.6, 36.4, 33.6, 32.7, 25.9. HRMS (TOF MS ESþ)
calcd for C28H32NO2 (MþH)þ: 414.2433; found: 414.2432. Anal.
calcd for (C28H31NO2): C, 81.32; H, 7.56; N, 3.39; found: C, 81.17; H,
7.61; N, 3.35.
3.1.3.2. 2-(4-Fluorophenethyl)-4a-(3-phenylpropyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (10b). Using Method C,
800 mg of 9a gave 600 mg 10b (54%). Mp 143e146 ꢁC; 1H NMR
(500 MHz, CDCl3):
d
7.26 (t, J ¼ 5.2 Hz, 3H), 7.18 (d, J ¼ 7.2 Hz, 1H),
7.10 (dd, J ¼ 12.0, 6.3 Hz, 3H), 6.95 (t, J ¼ 8.6 Hz, 2H), 6.66 (d,
J ¼ 8.4 Hz, 1H), 6.58 (dd, J ¼ 8.3, 2.3 Hz, 1H), 6.51 (d, J ¼ 2.2 Hz, 1H),
4.47e4.44 (m, 1H), 2.92e2.90 (m, 1H), 2.74 (t, J ¼ 7.7 Hz, 2H), 2.53
(dd, J ¼ 12.9, 6.2 Hz, 4H), 2.38 (dd, J ¼ 7.5, 2.6 Hz, 1H), 2.20 (t,
J ¼ 10.0 Hz, 1H), 2.04e2.01 (m, 1H), 1.80e1.78 (m, 1H), 1.71 (d,
J ¼ 12.4 Hz, 2H),1.57 (d, J ¼ 10.4 Hz, 2H). 13C NMR (126 MHz, CDCl3):
3.1.2.1. 4a-(3-Phenylpropyl)-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]
pyridin-6-ol (9a). Using Method B, 2.2 g of 8a gave 1.7 g 9a (96%). 1H
NMR (500 MHz, CDCl3):
d
7.21 (t, J ¼ 7.2 Hz, 2H), 7.11 (t, J ¼ 9.8 Hz,
3H), 6.56 (dd, J ¼ 20.1, 13.3 Hz, 3H), 4.24 (t, J ¼ 4.7 Hz, 1H), 2.98 (dd,
J ¼ 13.6, 4.2 Hz, 1H), 2.73 (dd, J ¼ 13.3, 5.8 Hz, 2H), 2.52 (d,
J ¼ 14.0 Hz, 3H), 1.83 (d, J ¼ 14.1 Hz, 1H), 1.70e1.51 (m, 5H). 13C NMR
d
162.5, 160.5, 152.9, 150.0, 142.1, 135.8, 135.81, 134.9, 130.1, 130.0,
(126 MHz, CDCl3):
d
161.9, 154.5, 152.6, 143.4, 133.1, 129.44, 129.36,
128.5, 128.4, 125.9, 115.3, 115.1, 114.5, 113.0, 110.8, 110.7, 84.9, 60.5,
60.4, 54.5, 49.8, 46.4, 39.4, 36.4, 32.6, 25.8. HRMS (TOF MS ESþ)
calcd for C28H31NFO2 (MþH)þ: 432.2339; found: 432.2334. Anal.
calcd for (C28H30NFO2): C, 77.93; H, 7.01; N, 3.25; found: C, 77.56; H,
7.01; N, 3.21.
126.8, 115.9, 111.6, 86.5, 48.0, 41.3, 40.9, 37.1, 32.9, 26.9. HRMS (TOF
MS ESþ) calcd for C20H24NO2 (MþH)þ: 310.1807; found: 310.1806.
3.1.2.2. 4a-(4-Phenylbutyl)-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]
pyridin-6-ol (9b). Using Method B, 2.2 g of 8b gave 1.7 g 9b (91%).
1H NMR (500 MHz, CDCl3):
d
7.15 (t, J ¼ 7.5 Hz, 2H), 7.05 (d,
3.1.3.3. (2-(2-Fluorophenethyl)-4a-(3-phenylpropyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (10c). Using Method C,
800 mg of 9a gave 530 mg 10c (47%). Mp 196e199 ꢁC; 1H NMR
J ¼ 7.3 Hz, 3H), 6.55 (dd, J ¼ 19.2, 8.1 Hz, 3H), 4.38 (t, J ¼ 3.7 Hz, 1H),
3.15 (dd, J ¼ 13.9, 3.4 Hz, 1H), 3.06 (t, J ¼ 7.0 Hz, 1H), 2.93e2.90 (m,
1H), 2.63 (dd, J ¼ 9.2, 4.0 Hz, 1H), 2.50 (t, J ¼ 7.5 Hz, 2H), 1.78 (d,
J ¼ 4.7 Hz, 2H),1.66 (ddd, J ¼ 23.9,12.4, 4.1 Hz, 2H),1.52 (t, J ¼ 7.5 Hz,
2H),1.29 (t, J ¼ 6.1 Hz,1H),1.18 (t, J ¼ 6.1 Hz,1H). 13C NMR (126 MHz,
(500 MHz, CDCl3):
d
7.25 (d, J ¼ 10.3 Hz, 3H), 7.14 (dt, J ¼ 24.0,
8.0 Hz, 3H), 7.02 (dd, J ¼ 23.8, 8.5 Hz, 3H), 6.65 (d, J ¼ 8.4 Hz, 1H),
6.59 (d, J ¼ 2.2 Hz, 1H), 6.51 (s, 1H), 4.46 (s, 1H), 2.93 (s, 1H), 2.81 (s,
3H), 2.57e2.52 (m, 3H), 2.38 (s, 1H), 2.24e2.22 (m, 1H), 2.04e2.01
CDCl3): d 153.2,152.7,143.7, 136.1,129.4,115.2,111.3, 111.1, 84.5, 47.5,
46.5, 42.3, 39.7, 36.7, 34.0, 33.4, 25.2, 24.6. HRMS (TOF MS ESþ)
(m,1H),1.80e1.79 (m, 2H),1.73e1.68 (m, 2H),1.62e1.53 (m, 2H). 13
C
calcd for C21H26NO2 (MþH)þ: 324.1964; found: 324.1975.
NMR (126 MHz, CDCl3): d 162.2, 160.3, 153.0, 150.0, 142.2, 131.1,
131.0, 128.5, 128.4, 128.0, 127.9, 127.8, 125.9, 124.2, 124.1, 115.4,
115.28, 114.5, 110.8, 85.3, 58.7, 54.4, 49.7, 46.3, 39.5, 36.3, 32.5, 26.7.
HRMS (TOF MS ESþ) calcd for C28H31NFO2 (MþH)þ: 432.2339;
found: 432.2334. Anal. calcd for (C28H30NFO2.0.25 H2O): C, 77.12; H,
7.05; N, 3.21; found: C, 77.37; H, 7.05; N, 3.21.
3.1.2.3. 4a-(5-Phenylpentyl)-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-
c]pyridin-6-ol (9c). Using Method B, 5.0 g of 8c gave 2.5 g 9c (58%).
1H NMR (500 MHz, CDCl3):
d
7.26 (t, J ¼ 7.3 Hz, 3H), 7.15 (dd, J ¼ 16.7,
7.4 Hz, 2H), 6.63 (d, J ¼ 8.2 Hz, 1H), 6.54e6.52 (m, 2H), 4.28 (t,
J ¼ 3.8 Hz, 1H), 3.02 (qd, J ¼ 14.6, 3.9 Hz, 2H), 2.77 (d, J ¼ 5.9 Hz, 1H),
2.66 (d, J ¼ 5.0 Hz, 1H), 2.56 (t, J ¼ 7.6 Hz, 2H), 1.69 (q, J ¼ 11.5 Hz,
3H), 1.57 (d, J ¼ 6.9 Hz, 3H), 1.28 (t, J ¼ 6.2 Hz, 4H). 13C NMR
3.1.3.4. 2,4a-Bis(3-phenylpropyl)-1,2,3,4,4a,9a-hexahydrobenzofuro
[2,3-c]pyridin-6-ol (10d). Using Method C, 550 mg of 9a gave
425 mg 10d (56%). Mp 152e155 ꢁC; 1H NMR (500 MHz, CDCl3):
(126 MHz, CDCl3):
d 152.6, 150.8, 142.7, 135.8, 128.5, 128.3, 125.8,
114.5, 110.7, 110.3, 83.9, 50.9, 46.3, 46.0, 41.5, 38.4, 36.0, 33.9, 31.4,
30.0, 24.1. HRMS (TOF MS ESþ) calcd for C22H28NO2 (MþH)þ:
338.2120; found: 338.2130.
d
7.25 (d, J ¼ 5.2 Hz, 5H), 7.14 (td, J ¼ 16.5, 7.1 Hz, 5H), 6.63 (d,
J ¼ 8.4 Hz, 1H), 6.56 (dd, J ¼ 8.4, 2.6 Hz, 1H), 6.49 (d, J ¼ 2.5 Hz, 1H),
4.41 (t, J ¼ 6.3 Hz, 1H), 2.84e2.81 (m, 1H), 2.58 (t, J ¼ 7.7 Hz, 3H),

536
M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
2.51 (dd, J ¼ 13.3, 7.6 Hz, 4H), 2.32 (d, J ¼ 6.6 Hz, 2H), 2.24 (t,
J ¼ 6.0 Hz, 1H), 2.10e2.05 (m, 1H), 2.01e1.97 (m, 1H), 1.80e1.67 (m,
128.5, 128.4, 126.3, 126.11, 125.9, 123.6, 114.6, 110.8, 110.8, 84.9, 63.4,
60.2, 49.7, 46.4, 39.5, 36.4, 32.6, 30.0, 25.8. HRMS (TOF MS ESþ)
calcd for C29H31NF3O2 (MþH)þ: 482.2307; found: 482.2283. Anal.
calcd for (C29H30NF3O2): C, 72.33; H, 6.28; N, 2.91; found: C, 72.04;
H, 6.17; N, 2.84.
4H), 1.59e1.52 (m, 8H). 13C NMR (126 MHz, CDCl3):
d 150.7, 142.1,
141.8, 134.4, 128.5, 128.4, 128.3, 125.9, 125.8, 114.7, 111.0, 110.6, 84.5,
57.9, 49.7, 46.3, 39.7, 36.3, 33.7, 32.2, 32.0, 28.1, 25.7. HRMS (TOF MS
ESþ) calcd for C29H34NO2 (MþH)þ: 428.2590; found: 428.2573.
Anal. calcd for (C29H33NO2$0.25 H2O): C, 80.61; H, 7.81; N, 3.24;
found: C, 80.65; H, 7.68; N, 3.26.
3.1.3.9. 4a-(3-Phenylpropyl)-2-(3-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 400 mg of 9a gave 170 mg 10i (27%). Mp
149e152 ꢁC; 1H NMR (500 MHz, CDCl3):
7.45e7.41 (m, 2H), 7.35
(10i).
3.1.3.5. 4a-(3-Phenylpropyl)-2-(4-(trifluoromethyl)phenethyl)-
d
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 500 mg of 9a gave 250 mg 10e (32%). Mp
139e142 ꢁC; 1H NMR (500 MHz, CDCl3):
(10e).
(d, J ¼ 18.0 Hz, 2H), 7.25 (d, J ¼ 10.5 Hz, 2H), 7.16 (dd, J ¼ 14.4, 7.1 Hz,
2H), 7.11 (d, J ¼ 7.2 Hz, 1H), 6.65 (d, J ¼ 8.4 Hz, 1H), 6.59 (s, 1H), 6.51
(d, J ¼ 2.1 Hz, 1H), 4.45 (d, J ¼ 5.6 Hz, 1H), 2.90 (dt, J ¼ 1.9, 0.9 Hz,
2H), 2.82 (t, J ¼ 7.5 Hz, 2H), 2.55 (dt, J ¼ 14.3, 6.8 Hz, 3H), 2.41e2.39
(m, 1H), 2.22 (t, J ¼ 9.2 Hz, 1H), 2.01 (d, J ¼ 13.5 Hz, 1H), 1.79e1.78
(m, 2H), 1.71e1.66 (m, 2H), 1.57 (t, J ¼ 10.0 Hz, 2H). 13C NMR
d
7.52 (d, J ¼ 7.7 Hz, 2H),
7.26 (d, J ¼ 7.9 Hz, 3H), 7.18 (d, J ¼ 7.0 Hz, 2H), 7.11 (d, J ¼ 7.2 Hz, 2H),
6.66 (d, J ¼ 8.3 Hz, 1H), 6.59e6.58 (m, 1H), 6.52 (s, 1H), 4.45 (t,
J ¼ 5.8 Hz, 1H), 2.91 (t, J ¼ 5.7 Hz, 1H), 2.82 (t, J ¼ 7.7 Hz, 2H), 2.55
(dt, J ¼ 11.3, 6.2 Hz, 4H), 2.39 (dd, J ¼ 11.6, 7.2 Hz, 1H), 2.21 (t,
J ¼ 13.9 Hz, 1H), 2.04e2.01 (m, 1H), 1.80e1.69 (m, 3H), 1.57 (q,
(126 MHz, CDCl3):
d 153.1, 150.4, 142.4, 132.5, 129.2, 128.8, 128.7,
126.2, 125.8, 125.7, 123.4, 123.4, 114.8, 111.1, 111.0, 85.2, 60.3, 54.7,
J ¼ 10.6 Hz, 2H). 13C NMR (126 MHz, CDCl3):
d 152.9, 150.0, 144.4,
50.1, 46.7, 39.7, 36.7, 33.6, 32.9, 26.1. HRMS (TOF MS ESþ) calcd for
142.1, 134.9, 129.1, 128.51, 128.4, 125.9, 125.44, 125.41, 123.3, 114.5,
113.0, 110.8, 110.7, 84.9, 59.9, 54.5, 49.8, 46.4, 39.4, 36.4, 33.4, 32.6,
25.8. HRMS (TOF MS ESþ) calcd for C29H31NF3O2 (MþH)þ:
482.2307; found: 482.2295. Anal. calcd for (C29H30NO2F3$0.25
H2O): C, 71.66; H, 6.32; N, 2.88; found: C, 71.58; H, 6.38; N, 2.91.
C
29H31NF3O2 (MþH)þ: 482.2307; found: 482.2283. Anal. calcd for
(C29H30NF3O2): C, 72.33; H, 6.28; N, 2.91; found: C, 72.18; H, 6.29; N,
2.83.
3.1.3.10. 2-Phenethyl-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-ol (11a). Using Method C, 200 mg of
9b gave 170 mg of 11a (64%). Mp 179e182 ꢁC; 1H NMR (500 MHz,
3.1.3.6. 2-Allyl-4a-phenethyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-
c]pyridin-6-ol (10f). Using Method C, 500 mg of 9a gave 125 mg 10f
CDCl3):
d
7.29e7.25 (m, 4H), 7.21e7.15 (m, 3H), 7.12 (d, J ¼ 7.1 Hz,
(25%). Mp 143e148 ꢁC; 1H NMR (500 MHz, CDCl3):
d
7.19e7.17 (m,
3H), 6.67 (d, J ¼ 8.4 Hz, 1H), 6.60 (dd, J ¼ 8.3, 2.5 Hz, 1H), 6.56 (d,
J ¼ 2.4 Hz, 1H), 4.48 (t, J ¼ 6.3 Hz, 1H), 2.95 (dd, J ¼ 12.0, 5.6 Hz, 1H),
2.80 (t, J ¼ 8.2 Hz, 2H), 2.57 (td, J ¼ 13.9, 5.9 Hz, 3H), 2.39 (dd,
J ¼ 12.0, 7.3 Hz, 1H), 2.23 (t, J ¼ 9.2 Hz, 1H), 2.05e2.02 (m, 2H), 1.83
(td, J ¼ 9.3, 4.5 Hz, 1H), 1.69 (dt, J ¼ 12.1, 6.1 Hz, 2H), 1.55 (t,
J ¼ 6.9 Hz, 3H), 1.29 (dt, J ¼ 12.0, 5.7 Hz, 2H). 13C NMR (126 MHz,
2H), 7.10 (d, J ¼ 7.0 Hz, 2H), 7.04 (d, J ¼ 7.2 Hz,1H), 6.57 (d, J ¼ 8.4 Hz,
1H), 6.52e6.50 (m, 1H), 6.43 (d, J ¼ 2.2 Hz, 1H), 5.79e5.74 (m, 1H),
5.08e5.05 (m, 2H), 4.36 (t, J ¼ 6.2 Hz, 1H), 2.88 (t, J ¼ 6.9 Hz, 2H),
2.77e2.74 (m, 1H), 2.46e2.41 (m, 3H), 2.19 (dd, J ¼ 12.2, 7.2 Hz, 1H),
2.05e2.01 (m, 1H), 1.94e1.91 (m, 1H), 1.68e1.60 (m, 2H), 1.52e1.46
(m, 2H). 13C NMR (126 MHz, CDCl3):
d
152.9, 149.9, 142.2, 135.0,
CDCl3): d 152.9, 150.1, 142.6, 140.2, 135.1, 128.8, 128.6, 128.5, 128.4,
134.8, 128.5, 128.4, 125.9, 118.4, 114.4, 113.0, 110.8, 85.0, 61.8, 54.4,
128.3, 126.2, 125.8, 114.5, 110.9, 110.8, 85.0, 60.6, 54.6, 49.9, 46.5,
49.7, 46.3, 39.4, 36.4, 32.7, 25.8. HRMS (TOF MS ESþ) calcd for
39.7, 35.8, 33.5, 32.5, 32.1, 23.7. HRMS (TOF MS ESþ) calcd for
C
23H28NO2 (MþH)þ: 350.2120; found: 350.2117. Anal. calcd for
C
29H34NO2 (MþH)þ: 428.2590; found: 428.2592. Anal. calcd for
(C23H27NO2$0.25 H2O): C, 78.04; H, 7.83; N, 3.96; found: C, 78.34; H,
(C29H33NO2): C, 81.46; H, 7.78; N, 3.28; found: C, 81.06; H, 7.57; N,
3.14.
7.83; N, 3.96.
3.1.3.7. 2 2-(Cyclopropylmethyl)-4a-phenylpropyl-1,2,3,4,4a,9a-hex-
ahydrobenzofuro[2,3-c]pyridin-6-ol (10g). Using Method C, 500 mg
of 9a gave 200 mg 10g (34%). Mp 166e169 ꢁC; 1H NMR (500 MHz,
3.1.3.11. 2-(4-Fluorophenethyl)-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (11b). Using Method C,
300 mg of 9b gave 170 mg 11b (41%). Mp 147e149 ꢁC; 1H NMR
CDCl3):
d
7.24 (s, 2H), 7.17 (d, J ¼ 6.8 Hz, 1H), 7.11 (d, J ¼ 6.9 Hz, 2H),
(500 MHz, CD3OD):
d
7.22e7.20 (m, 3H), 7.13 (d, J ¼ 7.2 Hz, 2H), 7.06
6.65 (d, J ¼ 8.1 Hz, 1H), 6.58 (d, J ¼ 6.9 Hz, 1H), 6.51 (s, 1H), 4.46 (s,
1H), 2.98e2.96 (m, 1H), 2.64e2.60 (m, 1H), 2.52 (d, J ¼ 5.3 Hz, 3H),
2.33e2.16 (m, 5H), 2.02 (dd, J ¼ 12.5, 0.6 Hz, 1H), 1.79 (s, 1H),
1.71e1.52 (m, 3H), 0.85e0.83 (m, 1H), 0.50 (d, J ¼ 7.0 Hz, 2H), 0.07
(t, J ¼ 7.9 Hz, 2H), 6.90 (t, J ¼ 8.6 Hz, 2H), 6.62 (d, J ¼ 8.4 Hz,1H), 6.55
(dd, J ¼ 8.4, 2.4 Hz, 1H), 6.50 (d, J ¼ 2.2 Hz, 1H), 4.41 (t, J ¼ 6.1 Hz,
1H), 2.87 (dd, J ¼ 11.7, 5.2 Hz, 1H), 2.71 (t, J ¼ 8.1 Hz, 2H), 2.50 (t,
J ¼ 7.8 Hz, 3H), 2.33 (dd, J ¼ 11.9, 7.2 Hz, 1H), 2.19e2.15 (m, 1H),
2.00e1.97 (m, 1H), 1.77 (dt, J ¼ 10.9, 5.9 Hz, 1H), 1.64 (dt, J ¼ 12.2,
6.2 Hz, 2H), 1.50 (t, J ¼ 7.8 Hz, 2H), 1.25 (dt, J ¼ 11.8, 6.2 Hz, 2H), 1.17
(s, 2H). 13C NMR (126 MHz, CDCl3):
d 153.0, 149.9, 142.2, 135.0,
135.0, 128.5, 128.4, 125.9, 114.4, 113.0, 110.8, 110.7, 85.1, 63.7, 54.2,
50.0, 48.7, 46.4, 39.5, 36.4, 32.5, 25.8, 8.2, 4.3. HRMS (TOF MS ESþ)
calcd for C24H30NO2 (MþH)þ: 364.2277; found: 364.2292. Anal.
calcd for (C24H29NO2): C, 79.30; H, 8.04; N, 3.85; found: C, 79.09; H,
7.93; N, 3.79.
(d, J ¼ 6.1 Hz, 2H). 13C NMR (126 MHz; CDCl3):
d 162.5, 160.6, 152.9,
150.0, 142.6, 135.9, 135.1, 130.2, 130.1, 128.5, 128.4, 125.8, 115.4,
115.2, 114.5, 110.9, 110.7, 85.0, 64.7, 60.6, 54.6, 49.9, 46.5, 35.7, 32.7,
32.5, 32.1, 32.0, 23.6. HRMS (TOF MS ESþ) calcd for C29H33NFO2
(MþH)þ: 446.2495; found: 446.2491. Anal. calcd for (C29H32NFO2):
C, 78.17; H, 7.24; N, 3.14; found: C, 77.90; H, 6.88; N, 3.08.
3.1.3.8. 4a-(3-Phenylpropyl)-2-(2-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 350 mg of 9a gave 122 mg 10h (22%). Mp
140e143 ꢁC; 1H NMR (500 MHz, CDCl3):
(10h).
3.1.3.12. 2-(2-Fluorophenethyl)-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (11c). Using Method C,
300 mg of 9b gave 175 mg 11c (42%). Mp 195e198 ꢁC; 1H NMR
d
7.60 (d, J ¼ 7.8 Hz, 1H),
7.43 (d, J ¼ 7.6 Hz, 2H), 7.30e7.24 (m, 3H), 7.17 (s, 1H), 7.11 (d,
J ¼ 7.4 Hz, 2H), 6.65 (d, J ¼ 8.3 Hz, 1H), 6.59e6.57 (m, 1H), 6.52 (s,
1H), 4.47 (s, 1H), 2.94e2.93 (m, 3H), 2.58e2.52 (m, 6H), 2.41 (dd,
J ¼ 1.9, 0.6 Hz, 1H), 2.24 (t, J ¼ 9.7 Hz, 1H), 2.02 (d, J ¼ 14.0 Hz, 1H),
(500 MHz, CDCl3):
d 7.25 (s, 3H), 7.18e7.12 (m, 4H), 7.06e6.98 (m,
2H), 6.67 (d, J ¼ 8.4 Hz, 1H), 6.59 (dd, J ¼ 8.4, 2.5 Hz, 1H), 6.55 (d,
J ¼ 2.4 Hz, 1H), 4.46 (t, J ¼ 6.3 Hz, 1H), 2.96e2.92 (m, 1H), 2.82 (t,
J ¼ 8.0 Hz, 2H), 2.57 (q, J ¼ 7.9 Hz, 4H), 2.39 (dd, J ¼ 12.0, 7.3 Hz, 1H),
2.25e2.21 (m, 1H), 2.03 (dt, J ¼ 11.3, 2.3 Hz, 1H), 1.83e1.79 (m, 1H),
1.81e1.78 (m, 1H), 1.72e1.68 (m, 1H), 1.57 (d, J ¼ 11.2 Hz, 3H). 13
C
NMR (126 MHz, CDCl3):
d 152.9, 150.1, 142.2, 138.8, 134.8, 131.8,

M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
537
1.70 (d, J ¼ 4.3 Hz, 2H), 1.56 (dd, J ¼ 15.9, 6.7 Hz, 4H), 1.33e1.26 (m,
2H). 13C NMR (126 MHz; CDCl3):
162.2, 160.2, 152.9, 149.8, 142.6,
7.41 (t, J ¼ 7.4 Hz, 1H), 7.27e7.21 (m, 4H), 7.11 (dd, J ¼ 27.4, 7.2 Hz,
3H), 6.64 (d, J ¼ 8.4 Hz, 1H), 6.57e6.55 (m, 1H), 6.52 (d, J ¼ 2.3 Hz,
1H), 4.44 (t, J ¼ 6.2 Hz, 1H), 2.92 (dd, J ¼ 9.5, 6.2 Hz, 3H), 2.54 (td,
J ¼ 13.4, 6.9 Hz, 4H), 2.39 (dd, J ¼ 11.9, 7.1 Hz, 1H), 2.22 (t, J ¼ 9.1 Hz,
1H), 2.02e1.99 (m, 1H), 1.79 (dt, J ¼ 10.8, 5.8 Hz, 1H), 1.67 (td,
d
135.1, 131.1, 131.0, 128.4, 127.9, 125.7, 124.1, 115.4, 115.2, 114.4, 110.8,
110.7, 85.0, 58.8, 54.4, 49.7, 46.4, 39.6, 35.8, 32.5, 32.1, 26.7, 23.6.
HRMS (TOF MS ESþ) calcd for C29H33NFO2 (MþH)þ: 446.2495;
found: 446.2491. Anal. calcd for (C29H32NFO2): C, 78.17; H, 7.24; N,
3.14; found: C, 78.01; H, 7.22; N, 3.03.
J ¼ 12.5, 4.8 Hz, 2H), 1.51 (t, J ¼ 6.8 Hz, 4H), 1.31e1.23 (m, 2H). 13
C
NMR (126 MHz; CD3OD):
d 152.9, 150.0, 142.6, 138.9, 135.1, 131.9,
131.8, 128.9, 128.7, 128.5, 128.4, 126.3, 126.2, 126.1, 125.8, 123.6,
114.5, 110.9, 110.8, 85.0, 60.3, 54.4, 49.6, 46.4, 39.7, 35.8, 32.7, 32.1,
30.0, 23.7. HRMS (TOF MS ESþ) calcd for C30H33NO2F3 (MþH)þ:
496.2463; found: 496.2480. Anal. calcd for (C30H32NO2F3): C, 72.71;
H, 6.51; N, 2.83; found: C, 72.42; H, 6.46; N, 2.79.
3.1.3.13. 4a-(4-Phenylbutyl)-2-(3-phenylpropyl)-1,2,3,4,4a,9a-hex-
ahydrobenzofuro[2,3-c]pyridin-6-ol (11d). Using Method C, 200 mg
of 9b gave 90 mg of 11d (33%). Mp 137e140 ꢁC; 1H NMR (500 MHz,
CDCl3):
d
7.33 (q, J ¼ 7.5 Hz, 3H), 7.27 (dd, J ¼ 10.0, 7.9 Hz, 3H), 7.22
(t, J ¼ 6.7 Hz, 2H), 7.17 (d, J ¼ 7.3 Hz, 2H), 6.72 (d, J ¼ 8.1 Hz, 1H),
6.65e6.63 (m, 2H), 4.54 (t, J ¼ 6.5 Hz, 1H), 2.98 (dd, J ¼ 11.9, 5.4 Hz,
1H), 2.79 (t, J ¼ 7.7 Hz, 1H), 2.62 (dt, J ¼ 31.8, 7.7 Hz, 4H), 2.43 (dd,
J ¼ 8.4, 4.5 Hz, 2H), 2.33 (dd, J ¼ 12.0, 7.6 Hz, 1H), 2.18 (t, J ¼ 9.5 Hz,
1H), 2.09e2.06 (m, 2H),1.98 (t, J ¼ 7.6 Hz,1H),1.90 (t, J ¼ 7.6 Hz, 2H),
1.72 (dt, J ¼ 12.4, 6.2 Hz, 1H), 1.58 (t, J ¼ 7.7 Hz, 2H), 1.35 (d,
J ¼ 5.5 Hz, 2H), 1.30 (d, J ¼ 6.2 Hz, 1H). 13C NMR (126 MHz, CDCl3):
3.1.3.17. 2,4a-Bis(4-phenylbutyl)-1,2,3,4,4a,9a-hexahydrobenzofuro
[2,3-c]pyridin-6-ol (11h). Using Method C, 200 mg of 9b gave
125 mg 11h (44%). Mp 168e172 ꢁC; 1H NMR (500 MHz, CDCl3):
d
7.26e7.24 (m, 5H), 7.16 (d, J ¼ 7.0 Hz, 3H), 7.11 (d, J ¼ 7.4 Hz, 2H),
6.65 (d, J ¼ 8.3 Hz, 1H), 6.59e6.56 (m, 1H), 6.52 (d, J ¼ 1.8 Hz, 1H),
4.43e4.41 (m, 1H), 2.84e2.81 (m, 1H), 2.57 (dt, J ¼ 28.9, 7.5 Hz, 3H),
2.48 (d, J ¼ 9.0 Hz, 1H), 2.33e2.29 (m, 2H), 2.25e2.21 (m, 2H),
2.09e2.05 (m, 2H), 2.00e1.97 (m, 2H), 1.78e1.75 (m, 1H), 1.68e1.64
(m, 2H), 1.55e1.50 (m, 4H), 1.30e1.26 (m, 2H). 13C NMR (126 MHz,
d
152.3, 150.6, 142.5, 141.8, 134.6, 128.5, 128.4, 128.3, 125.92, 125.8,
125.7, 114.6, 111.1, 110.6, 84.6, 62.2, 57.9, 54.4, 49.8, 46.4, 39.9, 35.8,
34.2, 33.7, 32.1, 32.0, 31.8, 28.1, 23.5. HRMS (TOF MS ESþ) calcd for
C
30H36NO2 (MþH)þ: 442.2746; found: 442.2758. Anal. calcd for
CDCl3): d 153.3, 150.1, 142.93, 142.83, 135.5, 128.83, 128.75, 128.72,
(C30H35NO2$0.25 H2O): C, 80.77; H, 8.02; N, 3.14; found: C, 81.03; H,
128.69, 128.64, 126.1, 114.6, 111.18, 111.01, 106.1, 85.5, 58.9, 55.1, 50.3,
46.8, 40.1, 36.22, 36.12, 32.8, 32.4, 29.8, 26.9, 23.9. HRMS (TOF MS
ESþ) calcd for C31H38NO2 (MþH)þ: 456.2903; found: 456.2920.
Anal. calcd for (C31H37NO2): C, 81.72; H, 8.19; N, 3.07; found: C,
81.57; H, 8.01; N, 2.93.
7.68; N, 3.12.
3.1.3.14. 4a-(4-Phenylbutyl)-2-(4-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 300 mg of 9b gave 200 mg 11e (44%). Mp
157e160 ꢁC; 1H NMR (500 MHz, CDCl3):
7.52 (d, J ¼ 7.9 Hz, 2H),
(11e).
d
3.1.3.18. 4a-(4-Phenylbutyl)-2-(3-(trifluoromethyl)phenethyl)-
7.26 (t, J ¼ 7.9 Hz, 4H), 7.17 (t, J ¼ 7.3 Hz, 1H), 7.13 (t, J ¼ 10.7 Hz, 2H),
6.67 (d, J ¼ 8.4 Hz, 1H), 6.59 (dd, J ¼ 8.4, 2.2 Hz, 1H), 6.54 (d,
J ¼ 2.0 Hz, 1H), 4.45 (t, J ¼ 6.1 Hz, 1H), 2.90 (dd, J ¼ 12.0, 5.1 Hz, 1H),
2.83 (t, J ¼ 8.0 Hz, 2H), 2.56 (dd, J ¼ 13.6, 7.7 Hz, 4H), 2.40 (dd,
J ¼ 12.0, 7.1 Hz,1H), 2.25e2.18 (m,1H), 2.03 (dd, J ¼ 10.0, 4.5 Hz,1H),
1.82e1.77 (m, 1H), 1.69 (dt, J ¼ 12.3, 6.3 Hz, 1H), 1.56 (td, J ¼ 16.5,
9.3 Hz, 5H), 1.32e1.22 (m, 2H), 1.22 (d, J ¼ 6.1 Hz, 1H). 13C NMR
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 350 mg of 9b gave 260 mg of 11i (37%). Mp
128e130 ꢁC; 1H NMR (500 MHz, CD3OD):
8.21 (tdd, J ¼ 24.8, 13.7,
(11i).
d
9.9 Hz, 3H), 8.08 (t, J ¼ 5.2 Hz, 3H), 8.00 (d, J ¼ 7.0 Hz, 1H), 7.94 (d,
J ¼ 7.4 Hz, 2H), 7.50 (d, J ¼ 8.4 Hz, 1H), 7.42 (d, J ¼ 8.5 Hz, 1H), 7.38
(d, J ¼ 1.0 Hz, 1H), 5.29 (t, J ¼ 6.1 Hz, 1H), 3.75 (dd, J ¼ 11.9, 5.2 Hz,
1H), 3.65 (q, J ¼ 8.4 Hz, 3H), 3.39 (td, J ¼ 14.2, 6.0 Hz, 4H), 3.23 (dd,
J ¼ 11.9, 7.2 Hz, 1H), 3.06 (t, J ¼ 9.4 Hz, 1H), 2.85 (d, J ¼ 14.2 Hz, 1H),
2.65 (dd, J ¼ 10.1, 3.2 Hz, 1H), 2.52 (td, J ¼ 12.5, 4.8 Hz, 2H), 2.37 (dt,
J ¼ 14.6, 7.4 Hz, 3H), 2.13 (t, J ¼ 6.6 Hz, 2H). 13C NMR (126 MHz;
(126 MHz; CD3OD):
d 152.9, 149.9, 144.5, 142.6, 135.1, 129.1, 128.5,
128.4, 125.8, 125.5, 125.4, 114.4, 110.9, 110.8, 85.0, 60.0, 54.5, 49.9,
46.4, 39.5, 35.8, 33.4, 32.6, 32.1, 23.7. HRMS (TOF MS ESþ) calcd for
C
30H33NO2F3 (MþH)þ: 496.2463; found: 496.2480. Anal. calcd for
CD3OD): d 152.8, 150.1, 142.6, 141.2, 135.1, 132.2, 130.9, 130.7, 128.9,
(C30H32NO2F3.0.25 H2O): C, 72.05; H, 6.55; N, 2.80; found: C, 72.25;
H, 6.58; N, 2.77.
128.5, 125.8, 125.6, 125.5, 123.2, 123.1, 114.5, 110.9, 110.7, 88.2, 84.9,
60.0, 54.5, 54.4, 49.9, 46.4, 39.6, 35.8, 33.3, 32.5, 23.7. HRMS (TOF
MS ESþ) calcd for C30H33NO2F3 (MþH)þ: 496.2463; found:
496.2480. Anal. calcd for (C30H32NO2F3): C, 72.71; H, 6.51; N, 2.83;
found: C, 72.40; H, 6.45; N, 2.90.
3.1.3.15. 2-(Cyclopropylmethyl)-4a-(4-phenylbutyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (11f). Using Method C,
250 mg 9b gave 150 mg 11f (51%). Mp 162e165 ꢁC; 1H NMR
(500 MHz, CD3OD):
d
7.25 (d, J ¼ 6.4 Hz, 2H), 7.16 (t, J ¼ 7.3 Hz, 1H),
3.1.3.19. 2-Phenethyl-4a-(5-phenylpentyl)-1,2,3,4,4a,9a-hexahy-
drobenzofuro[2,3-c]pyridin-6-ol (12a). Using Method C, 200 mg of
9c gave 150 mg 12a (57%). Mp 153e155 ꢁC; 1H NMR (500 MHz,
7.11 (d, J ¼ 7.2 Hz, 2H), 6.65 (d, J ¼ 8.4 Hz, 1H), 6.59e6.57 (m, 1H),
6.53 (d, J ¼ 2.5 Hz,1H), 4.47 (t, J ¼ 6.1 Hz,1H), 3.00 (d, J ¼ 6.3 Hz,1H),
2.65 (dd, J ¼ 2.5, 1.2 Hz, 1H), 2.54 (t, J ¼ 7.8 Hz, 3H), 2.34 (d,
J ¼ 3.4 Hz, 1H), 2.27e2.18 (m, 2H), 2.02 (ddd, J ¼ 14.0, 4.9, 3.3 Hz,
1H), 1.83 (d, J ¼ 9.4 Hz, 2H), 1.67 (t, J ¼ 6.0 Hz, 2H), 1.54 (dd, J ¼ 15.5,
7.7 Hz, 2H), 1.31e1.26 (m, 2H), 0.86 (t, J ¼ 4.6 Hz, 1H), 0.50 (d,
CDCl3):
d
7.26 (d, J ¼ 1.5 Hz, 5H), 7.16 (q, J ¼ 10.2 Hz, 5H), 6.66 (dd,
J ¼ 8.0, 0.8 Hz, 1H), 6.59e6.56 (m, 2H), 4.98 (s, 1H), 4.47 (t,
J ¼ 5.3 Hz, 1H), 2.91 (dd, J ¼ 11.7, 4.6 Hz, 1H), 2.79 (t, J ¼ 8.0 Hz, 2H),
2.55 (dd, J ¼ 14.3, 7.4 Hz, 5H), 2.42e2.39 (m, 1H), 2.25e2.21 (m, 1H),
2.03 (d, J ¼ 14.1 Hz, 1H), 1.81e1.77 (m, 1H), 1.66 (s, 3H), 1.55e1.49
J ¼ 7.7 Hz, 2H), 0.07 (s, 2H). 13C NMR (126 MHz; CDCl3):
d 152.8,
150.1, 142.6, 135.1, 128.4, 128.3, 125.8, 114.4, 110.9, 110.7, 84.9, 63.7,
54.4, 49.9, 46.5, 39.7, 35.8, 32.3, 32.1, 23.6, 8.1, 4.2, 4.1. HRMS (TOF
MS ESþ) calcd for C25H32NO2 (MþH)þ: 378.2433; found: 378.2433.
Anal. calcd for (C25H31NO2): C, 79.54; H, 8.28; N, 3.71; found: C,
81.03; H, 7.68; N, 3.12.
(m, 2H), 1.24 (s, 2H). 13C NMR (126 MHz, CDCl3):
d 152.8, 152.7,
149.9, 149.8, 142.8, 142.7, 140.2, 140.1, 135.2, 128.8, 128.3, 126.2,
126.1, 125.7, 114.3, 110.8, 110.7, 84.9, 60.6, 54.5, 49.9, 46.4, 36.0, 35.9,
33.5, 32.7, 31.5, 29.9, 23.8. HRMS (TOF MS APþ) calcd for C30H36NO2
(MþH)þ: 442.2740; found: 442.2746. Anal. calcd for (C30H35NO2):
C, 81.59; H, 7.99; N, 3.17; found: C, 81.45; H, 8.24; N, 3.00.
3.1.3.16. 4a-(4-Phenylbutyl)-2-(2-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 200 mg of 9b gave 105 mg 11g (34%). Mp
161e164 ꢁC; 1H NMR (500 MHz, CD3OD):
7.57 (d, J ¼ 7.7 Hz, 1H),
(11g).
3.1.3.20. 2-(4-Fluorophenethyl)-4a-(5-phenylpentyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (12b). Using Method C,
300 mg of 9c gave 205 mg 12b (50%). Mp 132e135 ꢁC; 1H NMR
d

538
M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
(500 MHz, CDCl3):
d
7.28e7.25 (m, 3H), 7.16e7.09 (m, 4H),
7.44 (t, J ¼ 7.4 Hz, 1H), 7.27 (q, J ¼ 9.7 Hz, 4H), 7.15 (dd, J ¼ 18.7,
7.3 Hz, 3H), 6.65 (d, J ¼ 8.4 Hz, 1H), 6.59 (dd, J ¼ 11.9, 3.4 Hz, 2H),
4.47 (t, J ¼ 5.8 Hz, 1H), 2.95 (d, J ¼ 6.1 Hz, 3H), 2.60e2.53 (m, 5H),
2.46e2.43 (m, 1H), 2.26 (t, J ¼ 7.8 Hz, 1H), 2.04e2.01 (m, 1H), 1.81 (s,
1H), 1.62e1.49 (m, 4H), 1.26 (s, 4H), 0.89e0.88 (m, 1H). 13C NMR
6.96e6.93 (m, 2H), 6.66e6.65 (m, 1H), 6.59e6.55 (m, 2H), 4.51 (s,
1H), 4.45e4.43 (m, 1H), 2.90e2.87 (m, 1H), 2.76e2.73 (m, 2H),
2.57e2.52 (m, 4H), 2.39 (dd, J ¼ 12.1, 7.5 Hz, 1H), 2.24e2.17 (m, 1H),
2.01 (d, J ¼ 14.3 Hz, 1H), 1.81e1.76 (m, 1H), 1.64 (t, J ¼ 7.7 Hz, 1H),
1.56 (s, 4H), 1.50 (t, J ¼ 8.5 Hz, 1H), 1.26e1.21 (m, 2H). 13C NMR
(126 MHz, CDCl3):
d 152.6, 152.4, 150.3, 150.2, 142.8, 142.7, 138.7,
(126 MHz, CDCl3):
d
162.5, 153.0, 149.9, 142.8, 136.0, 135.9, 135.3,
135.0, 131.9, 128.8, 128.6, 126.4, 126.3, 126.1, 126.0, 125.7, 125.6,
123.5, 114.5, 110.8, 110.7, 84.8, 60.3, 54.2, 49.6, 46.3, 39.7, 39.5, 36.0,
32.4, 31.5, 29.8, 23.8. HRMS (TOF MS ESþ) calcd for C31H35NO2F3
(MþH)þ: 510.2620; found: 510.2618. Anal. calcd for
(C31H34NO2F3.0.25 H2O): C, 72.42; H, 6.76; N, 2.72; found: C, 72.14;
H, 6.69; N, 2.59.
130.2, 130.1, 128.5, 128.3, 125.8, 115.3, 115.2, 114.4, 110.8, 110.7, 85.1,
60.6, 54.6, 49.9, 46.4, 39.7, 36.0, 32.9, 32.8, 31.4, 29.9, 23.9. HRMS
(TOF MS ESþ) calcd for C30H35NFO2 (MþH)þ: 460.2652; found:
460.2639. Anal. calcd for (C30H34NFO2.0.25 H2O): C, 77.64; H, 7.49;
N, 3.02; found: C, 77.85; H, 7.27; N, 2.74.
3.1.3.21. 2-(2-Fluorophenethyl)-4a-(5-phenylpentyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (12c). Using Method C,
250 mg of 9c gave 120 mg of 12c (35%). Mp 180e183 ꢁC; 1H NMR
3.1.4. Opioid binding assays
As previously described [14,15], the recombinant CHO cells
(hMOR-CHO, hDOR-CHO and hKOR-CHO) were produced by stable
transfection with the respective human opioid receptor cDNA, and
provided by Dr. Larry Toll (SRI International, CA). The cells were
grown in plastic flasks in DMEM (90%) (hDOR-CHO and hKOR-CHO)
or DMEM/F-12 (45%/45%) medium (hMOR-CHO) containing 5% FBS
(Invitrogen), 5% FetalClone II (HyClone), and Geneticin (G-418:
0.10e0.2 mg/mL) (Invitrogen) under 95% air/5% CO2 at 37 ꢁC. Cell
monolayers were harvested and frozen in ꢀ80 ꢁC. The hKOR-CHO,
hMOR-CHO and hDOR-CHO cells are used for opioid binding ex-
(500 MHz, CDCl3):
d
7.26 (d, J ¼ 5.1 Hz, 4H), 7.15 (dd, J ¼ 14.1, 5.7 Hz,
4H), 7.06e6.98 (m, 2H), 6.66 (d, J ¼ 8.2 Hz, 1H), 6.59e6.56 (m, 1H),
4.46 (t, J ¼ 6.0 Hz, 1H), 2.94e2.90 (m, 1H), 2.82 (t, J ¼ 7.8 Hz, 2H),
2.55 (t, J ¼ 7.6 Hz, 4H), 2.40 (dd, J ¼ 11.9, 7.0 Hz, 1H), 2.23e2.22 (m,
1H), 2.18 (d, J ¼ 5.3 Hz, 1H), 2.03e2.01 (m, 1H), 1.79e1.77 (m, 1H),
1.63 (s, 3H), 1.56e1.49 (m, 2H), 1.24 (s, 2H). 13C NMR (126 MHz;
CDCl3):
d 168.0, 162.2, 160.3, 152.4, 150.8, 142.7, 134.8, 132.6, 131.1,
128.5, 126.9, 125.7, 124.2, 115.4, 114.6, 111.0, 110.7, 84.7, 68.3, 58.7,
54.2, 49.7, 36.0, 32.3, 31.4, 30.5, 29.1, 26.6, 23.8. HRMS (TOF MS ESþ)
calcd for C30H35NFO2 (MþH)þ: 460.2652; found: 460.2639. Anal.
calcd for (C30H34NFO2.0.25 H2O): C, 77.64; H, 7.49; N, 3.02; found: C,
77.75; H, 7.39; N, 2.98.
periments. For the [35S]-GTP-
hKOR-CHO and hMOR-CHO cells for assaying KOR and MOR re-
g-S binding experiments, we use
ceptor
function.
Currently,
we
use
the
NG108-15
g-S binding
neuroblastoma ꢂ glioma cell for the DOR [35S]-GTP-
assay, and obtain an excellent signal-to-noise ratio. In summary, we
use the hDOR-CHO cells for DOR binding assays, and the NG108-15
3.1.3.22. 4a-(5-Phenylpentyl)-2-(4-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 300 mg of 9c gave 115 mg of 12d (25%). Mp
124e127 ꢁC; 1H NMR (500 MHz, CDCl3):
(12d).
cells for the DOR [35S]-GTP-
g-S binding assay.
As noted formerly [15,16], [3H][D-Ala2-MePhe4,Gly-ol5]
enkephalin ([3H]DAMGO, SA ¼ 44e48 Ci/mmol) was used to label
MOR, [3H][D-Ala2,D-Leu5]enkephalin ([3H]DADLE, SA ¼ 40e50 Ci/
mmol) to label DOR and [3H](ꢀ)-U69,593 (SA ¼ 50 Ci/mmol) to
label KOR binding sites. On the day of the assay, cell pellets were
thawed on ice for 15 min then homogenized with a polytron in
10 mL/pellet of ice-cold 10 mM TriseHCl, pH 7.4. Membranes were
then centrifuged at 30,000 ꢂ g for 10 min, resuspended in 10 mL/
pellet ice-cold 10 mM TriseHCl, pH 7.4 and again centrifuged
30,000 ꢂ g for 10 min. Membranes were then resuspended in 25 ꢁC
50 mM TriseHCl, pH 7.4 (~100 mL/pellet hMOR-CHO, 50 mL/pellet
hDOR-CHO and 120 mL/pellet hKOR-CHO). All assays took place in
50 mM TriseHCl, pH 7.4, with a protease inhibitor cocktail [baci-
d
7.51 (d, J ¼ 7.8 Hz, 2H),
7.26 (t, J ¼ 8.8 Hz, 4H), 7.14 (t, J ¼ 11.4 Hz, 3H), 6.66 (d, J ¼ 8.2 Hz,
1H), 6.57 (d, J ¼ 10.7 Hz, 2H), 4.46 (t, J ¼ 5.6 Hz, 1H), 2.87 (dt,
J ¼ 33.8, 6.6 Hz, 3H), 2.55 (q, J ¼ 8.1 Hz, 6H), 2.43 (dt, J ¼ 8.7, 4.5 Hz,
1H), 2.24 (t, J ¼ 9.0 Hz, 1H), 2.03e2.00 (m, 1H), 1.79 (t, J ¼ 9.6 Hz,
1H), 1.63 (d, J ¼ 9.4 Hz, 2H), 1.55e1.49 (m, 2H), 1.24 (d, J ¼ 2.1 Hz,
2H). 13C NMR (126 MHz, CDCl3):
d 152.6, 150.0, 144.2, 142.7, 135.1,
129.1, 128.5, 128.3, 125.7, 125.4, 125.4, 123.3, 114.4, 110.8, 110.7, 84.7,
69.1, 60.1, 54.3, 49.8, 46.2, 39.3, 36.0, 33.3, 32.6, 31.5, 29.9, 23.9.
HRMS (TOF MS ESþ) calcd for C31H35NO2F3 (MþH)þ: 510.2620;
found: 510.2618. Anal. calcd for (C31H34NO2F3): C, 73.06; H, 6.72; N,
2.75; found: C, 72.68; H, 6.67; N, 2.63.
tracin (100
chymostatin (2
dilution curves were made up with buffer containing 1 mg/mL BSA.
m
g/mL), bestatin (10
mg/mL), leupeptin (4 mg/mL) and
3.1.3.23. 2-(Cyclopropylmethyl)-4a-(5-phenylpentyl)-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ol (12e). Using Method C,
150 mg of 9c gave 72 mg of 12e (41%). Mp 141e144 ꢁC; 1H NMR
mg/mL)], in a final assay volume of 1.0 mL. All drug
Nonspecific binding was determined using 20
mM levallorphan
(500 MHz, CDCl3):
d
7.26 (t, J ¼ 7.3 Hz, 3H), 7.15 (dd, J ¼ 18.8, 7.6 Hz,
([3H]DAMGO and [3H]DADLE) and 1
m
M (ꢀ)-U69,593 (for [3H]
2H), 6.64 (d, J ¼ 8.2 Hz, 1H), 6.56 (dd, J ¼ 11.2, 2.9 Hz, 2H), 4.45 (t,
J ¼ 6.3 Hz, 1H), 2.96 (dd, J ¼ 12.0, 5.4 Hz, 1H), 2.62 (d, J ¼ 6.1 Hz, 1H),
2.54 (t, J ¼ 7.6 Hz, 3H), 2.34 (dd, J ¼ 12.1, 7.3 Hz, 2H), 2.25e2.18 (m,
3H), 2.03e1.99 (m, 1H), 1.82e1.77 (m, 1H), 1.61e1.55 (m, 4H),
1.50e1.48 (m, 1H), 1.25 (s, 3H), 0.86e0.83 (m, 1H), 0.50 (d,
J ¼ 8.0 Hz, 1H), 0.06 (d, J ¼ 3.2 Hz, 1H). 13C NMR (126 MHz, CDCl3):
U69,593 binding). [3H]Radioligands were used at ~ 2 nM concen-
trations. Triplicate samples were filtered with Brandel Cell Har-
vesters (Biomedical Research & Development Inc., Gaithersburg,
MD), over Whatman GF/B filters, after a 2 h incubation at 25 ꢁC. The
filters were punched into 24-well plates to which was added 0.6 mL
of LSC-cocktail (Cytoscint). Samples were counted, after an over-
night extraction, in a Trilux liquid scintillation counter at 44% ef-
d
153.0, 149.9, 142.8, 135.3, 128.5, 128.3, 125.7, 114.3, 110.8, 110.7,
85.1, 63.8, 54.5, 50.0, 46.4, 39.8, 36.0, 32.6, 31.4, 29.9, 23.9, 8.2, 4.19,
4.07. HRMS (MS APþ) calcd for C26H34NO22 (MþH)þ: 392.2590;
found: 392.2586. Anal. calcd for (C26H33NO2): C, 79.76; H, 8.50; N,
3.58; found: C, 79.40; H, 8.49; N, 3.45.
ficiency. Opioid binding assays had ~30 mg protein per assay tube.
Inhibition curves were generated by displacing a single concen-
tration of radioligand by 10 concentrations of drug. The pooled data
of three experiments (typically 30 data points) were fit to the two-
parameter logistic equation for the best-fit estimates of the IC50 and
N values: Y ¼ 100/(1 þ ([INHIBITOR]/IC50)N), where “Y” is the
percent of control value. Ki values for test drugs are calculated ac-
cording to the standard equation: Ki ¼ IC50/(1 þ [radioligand]/Kd]).
For the [3H]radioligands, the following Kd values (nM SD, n ¼ 3)
3.1.3.24. 4a-(5-Phenylpentyl)-2-(2-(trifluoromethyl)phenethyl)-
1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol
Using Method C, 200 mg of 9c gave 105 mg of 12f (35%). Mp
138e141 ꢁC; 1H NMR (500 MHz, CDCl3):
7.60 (d, J ¼ 7.6 Hz, 1H),
(12f).
d

M.R. Iyer et al. / European Journal of Medicinal Chemistry 92 (2015) 531e539
539
were used in the Ki calculation: [3H]DAMGO (0.93
DADLE (1.9 0.3) and [3H](ꢀ)-U69,593 (11 0.6).
0.04), [3H]
mediated phenomena. 38. An expeditious synthesis of rac-cis-4a-ethyl-2-
methyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol and rac-cis-2-
methyl-4a-phenethyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-6-ol,
Heterocycles 79 (2009) 1061e1072.
3.1.5. [35S]GTP-
g-S binding assays
[2] Y. Zhang, Y.S. Lee, R.B. Rothman, C.M. Dersch, J.R. Deschamps, A.E. Jacobson,
K.C. Rice, Probes for narcotic receptor mediated phenomena. 39. Enantiomeric
N-substituted benzofuro[2,3-c]pyridin-6-ols: synthesis and topological rela-
tionship to oxide-bridged phenylmorphans, J. Med. Chem. 52 (2009)
7570e7579.
As previously described [15,16], the assays were conducted with
minor modifications of published methods [17]. In this description,
buffer “A” is 50 mM TriseHCl, pH 7.4, containing 100 mM NaCl,
10 mM MgCl2, 1 mM EDTA and buffer “B” is buffer A plus 1.67 mM
DTT and 0.15% BSA. On the day of the assay, cells were thawed on ice
for 15 min and homogenized using a polytron in 50 mM TriseHCl,
[3] M.R. Iyer, Y.S. Lee, J.R. Deschamps, R.B. Rothman, C.M. Dersch, A.E. Jacobson,
K.C. Rice, Probes for narcotic receptor mediated phenomena. 40. N-Substituted
cis-4a-ethyl-1,2,3,4,4a,9a-hexahydrobenzofuro[2,3-c]pyridin-8-ols,
Med. Chem. 18 (2010) 91e99.
Bioorg.
[4] A.J. Hutchison, R. de Jesus, M. Williams, J.P. Simke, R.F. Neale, R.H. Jackson,
F. Ambrose, B.J. Barbaz, M.A. Sills, Benzofuro[2,3-c]pyridin-6-ols: synthesis,
affinity for opioid-receptor subtypes and antinociceptive activity, J. Med.
Chem. 32 (1989) 2221e2226.
[5] H.I. Mosberg, L. Yeomans, A.A. Harland, A.M. Bender, K. Sobczyk-Kojiro,
J.P. Anand, M.J. Clark, E.M. Jutkiewicz, J.R. Traynor, Opioid peptidomimetics:
pH 7.4, containing 4
mL bestatin and 100
mg/mL leupeptin, 2 mg/mL chymostatin, 10 mg/
m
g/mL bacitracin. The homogenate was
centrifuged at 30,000 ꢂ g for 10 min at 4 ꢁC, and the supernatant
discarded. The membrane pellets were resuspended in buffer B and
used for [35S]GTP-
g
-S binding assays. Test tubes received the
following additions: 50 L buffer A plus 0.1% BSA, 50 L GDP in
buffer A/0.1% BSA (final concentration ¼ 40 M), 50 L drug in
buffer A/0.1% BSA, 50 -S in buffer A/0.1% BSA (final
L [35S]-GTP-
concentration ¼ 50 pM), and 300 L of cell membranes (50 g of
protein) in buffer B. The final concentrations of reagents in the [35S]
GTP- -S binding assays were: 50 mM TriseHCl, pH 7.4, containing
100 mM NaCl, 10 mM MgCl2, 1 mM EDTA, 1 mM DTT, 40 M GDP
and 0.1% BSA. Incubations proceeded for 3 h at 25 ꢁC. Nonspecific
binding was determined using GTP- -S (40 M). Bound and free
35S]GTP-
-S was separated by vacuum filtration (Brandel) through
leads for the design of bioavailable mixed efficacy
agonist/ opioid receptor (DOR) antagonist ligands, J. Med. Chem. 56 (2013)
2139e2149.
m opioid receptor (MOR)
m
m
d
m
m
[6] E.E. Abdelhamid, M. Sultana, P.S. Portoghese, A.E. Takemori, Selective blockage
of delta opioid receptors prevents the development of morphine tolerance
and dependence in mice, J. Pharmacol. Exp. Ther. 258 (1991) 299e303.
[7] S. Ananthan, S. Saini, C. Dersch, H. Xu, N. McGlinchey, D. Giuvelis, E.J. Bilsky,
R.B. Rothman, 14-Alkoxy- and 14-acyloxypyridomorphinans: Mu agonist/
delta antagonist opioid analgesics with diminished tolerance and dependence
side effects, J. Med. Chem. 55 (2012) 8350e8363.
[8] Y.F. Su, R.W. McNutt, K.J. Chang, Delta-opioid ligands reverse alfentanil-
induced respiratory depression but not antinociception, J. Pharmacol. Exp.
Ther. 287 (1998) 815e823.
[9] M. Kurimura, H. Liu, A. Sulima, A.K. Przybyl, E. Ohshima, S. Kodato,
J.R. Deschamps, C. Dersch, R.B. Rothman, Y.S. Lee, A.E. Jacobson, K.C. Rice,
Probes for narcotic receptor mediated phenomena. 37. Synthesis and opioid
binding affinity of the final pair of oxide-bridged phenylmorphans, the ortho-
and para-b isomers and their N-phenethyl analogues, and the synthesis of the
N-phenethyl analogues of the ortho- and para-d isomers, J. Med. Chem. 51
(2008) 7866e7881.
[10] J.T.M. Linders, S. Mirsadeghi, J.L. Flippen-Anderson, C. George, A.E. Jacobson,
K.C. Rice, Probes for narcotic receptor mediated phenomena. Part 30. Syn-
thesis of rac-(3R,6aS,11aR)-2-methyl-1,3,4,5,6,11a-hexahydro-2H-3,6a-meth-
anobenzofuro[2,3-c]azocin-8-ol, an epoxy isomer of 5-phenylmorphan, Helv.
Chim. Acta 86 (2003) 484e493.
m
g
m
m
g
m
g
m
[
g
GF/B filters. The filters were punched into 24-well plates to which
was added 0.6 mL LSC-cocktail (Cytoscint). Samples were counted,
after an overnight extraction, in a Trilux liquid scintillation counter
at 27% efficiency.
For the [35S]GTP-
g-S binding experiments [15,16], Ke values
were determined using the “shift” experimental design, agonist
(DAMGO) doseeresponse curves were generated, using hMOR-CHO
cells, in the absence and presence (ten points/curve) of a test
compound. The data of several experiments, 3 or more, were
pooled, and the Ke values were calculated according to the equa-
tion: [Test Drug]/(EC50-2/EC50-1 ꢀ 1), where EC50-2 is the EC50 value
in the presence of the test drug and EC50-1 is the value in the
absence of the test drug.
[11] T.R. Burke Jr., A.E. Jacobson, K.C. Rice, B.A. Weissman, H.C. Huang,
J.V. Silverton, Probes for narcotic receptor mediated phenomena. 9. Synthesis
of
( )-(3a,6aa,11ab)-1,3,4,5,6,11a-hexahydro-2-methyl-2H-3,6a-meth-
anobenzofuro[2,3-c]azocin-10-ol, an oxide-bridged 5-(m-hydroxyphenyl)
morphan, J. Med. Chem. 29 (1986) 748e751.
[12] M. Iyer, R. Rothman, C. Dersch, A. Jacobson, K. Rice, Probes for narcotic re-
ceptor mediated phenomena. 47. Novel C4a- and N-substituted-1,2,3,4,4a,9a-
hexahydrobenzofuro[2,3-c]pyridin-6-ols, Bioorg. Med. Chem. 21 (2013)
3298e3309.
Acknowledgments
[13] B.B. Land, M.R. Bruchas, J.C. Lemos, M. Xu, E.J. Melief, C. Chavkin, The
The work of the Drug Design and Synthesis Section, was sup-
ported by the NIH Intramural Research Programs of the National
Institute on Drug Abuse (NIDA) and the National Institute of
Alcohol Abuse and Alcoholism. The Clinical Psychopharmacology
Section, CBRB, NIDA, was supported by the NIH Intramural
Research Program of the National Institute on Drug Abuse (NIDA).
We also thank Dr. Klaus Gawrisch and Dr. Walter Teague (Labora-
tory of Membrane Biochemistry and Biophysics, NIAAA, for NMR
spectral data. The authors express their thanks to Noel Whittaker,
Mass Spectrometry Facility, NIDDK, for mass spectral data.
dysphoric component of stress is encoded by activation of the dynorphin k-
opioid system, J. Neurosci. 28 (2008) 407e414.
[14] G. Fontana, G. Savona, B. Rodriguez, C.M. Dersch, R.B. Rothman,
T.E. Prisinzano, Synthetic studies of neoclerodane diterpenoids from Salvia
splendens and evaluation of opioid receptor affinity, Tetrahedron 64 (2008)
10041e10048.
[15] F. Li, C.M. Dersch, R.B. Rothman, J.R. Deschamps, A.E. Jacobson, K.C. Rice,
Probes for narcotic receptor mediated phenomena. 46. N-Substituted-
2,3,4,9,10,10a-hexahydro-1H-1,4a-(epiminoethano)phenanthren-6- and 8-ols
- carbocyclic relatives of f-oxide bridged phenylmorphans, Eur. J. Med. Chem.
58 (2012) 557e567.
[16] M.R. Iyer, Y.S. Lee, J.R. Deschamps, C.M. Dersch, R.B. Rothman, A.E. Jacobson,
K.C. Rice, Probes for narcotic receptor mediated phenomena. 44. Synthesis of
an N-substituted 4-hydroxy-5-(3-hydroxyphenyl)morphan with high affinity
and selective m-antagonist activity, Eur. J. Med. Chem. 50 (2012) 44e54.
Appendix A. Supplementary data
[17] H. Xu, A. Hashimoto, K.C. Rice, A.E. Jacobson, J.B. Thomas, F.I. Carroll, J. Lai,
R.B. Rothman, Opioid peptide receptor studies. 14. Stereochemistry de-
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2015.01.025.
termines agonist efficacy and intrinsic efficacy in the [35S]GTP-
binding assay, Synapse 39 (2001) 64e69.
g-S functional
References
[1] M.R. Iyer, J.R. Deschamps, A.E. Jacobson, K.C. Rice, Probes for narcotic receptor