Potent and Selective Tetrahydroisoquinoline Kappa Opioid Receptor Antagonists of Lead Compound (3 R)-7-Hydroxy- N-[(1 S)-2-methyl-1-(piperidin-1-ylmethyl)propyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxamide (PDTic)

Article abstract of DOI:10.1021/acs.jmedchem.8b00673

Past studies have shown that it has been difficult to discover and develop potent and selective κ opioid receptor antagonists, particularly compounds having potential for clinical development. In this study, we present a structure-activity relationship (SAR) study of a recently discovered new class of tetrahydroisoquinoline κ opioid receptor antagonists which led to (3R)-7-hydroxy-N-{(1S)-2-methyl-1-[(-4-methylpiperidine-1-yl)methyl]propyl}-1,2,3,4-tetrahydroisoquinoline-3-carboxamide (12) (4-Me-PDTic). Compound 12 had a K_e = 0.37 nM in a [³⁵S]GTPγS binding assay and was 645- and >8100-fold selective for the κ relative to the μ and δ opioid receptors, respectively. Calculated log BB and CNS (central nervous system) multiparameter optimization (MPO) and low molecular weight values all predict that 12 will penetrate the brain, and pharmacokinetic studies in rats show that 12 does indeed penetrate the brain.

Full text of DOI:10.1021/acs.jmedchem.8b00673

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Article
Potent and Selective Tetrahydroisoquinoline Kappa Opioid
Receptor Antagonists of Lead Compound (3R)-7-Hydroxy-
N-[(1S)-2-methyl-1-(piperidin-1-ylmethyl)propyl]-1,2,3,4-
tetrahydroisoquinoline-3-carboxamide (PDTic)
Pauline W Ondachi, Chad M. Kormos, Scott P Runyon, James B. Thomas, S. Wayne Mascarella,
Ann M. Decker, Hernán A. Navarro, Timothy Raymond Fennell, Rodney W. Snyder, and F. Ivy Carroll
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.8b00673 • Publication Date (Web): 17 Aug 2018
Downloaded from http://pubs.acs.org on August 17, 2018
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Potent and Selective Tetrahydroisoquinoline Kappa
Opioid Receptor Antagonists of Lead Compound
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(3R)ꢀ7ꢀHydroxyꢀNꢀ[(1S)ꢀ2ꢀmethylꢀ1ꢀ(piperidinꢀ1ꢀ
ylmethyl)propyl]ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀ
carboxamide (PDTic)
Pauline W. Ondachi, Chad M. Kormos, Scott P. Runyon, James B. Thomas, S. Wayne
Mascarella, Ann M. Decker, Hernán A. Navarro, Timothy R. Fennell, Rodney W. Snyder, and F.
Ivy Carroll*
Research Triangle Institute, PO Box 12194, Research Triangle Park, North Carolina 27709ꢀ
2194, United States
KEYWORDS: Kappa opioid receptor, antagonist, tetrahydroisoquinoline, functional assay,
pharmacokinetics
ABSTRACT: Past studies have shown that it has been difficult to discover and develop potent
and selective κ opioid receptor antagonists, particularly compounds having potential for clinical
development. In this study, we present a structural activity relationship (SAR) study of a recently
discovered new class of tetrahydroisoquinoline κ opioid receptor antagonists which led to (3R)ꢀ
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ꢀhydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[(ꢀ4ꢀmethylpiperidineꢀ1ꢀyl)methyl]propyl}ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (12) (4ꢀMeꢀPDTic). Compound 12 had a K = 0.37 nM in
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a [ S]GTPγS binding assay and was 645ꢀ and >8100ꢀfold selective for the κ relative to the ꢁ and
δ opioid receptors, respectively. Calculated logBB and CNS (central nervous system)
multiparameter optimization (MPO) and low molecular weight values all predict that 12 will
penetrate the brain and pharmacokinetic studies in rats shows that 12 does indeed penetrate the
brain.
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INTRODUCTION
Over the years it has proven to be very difficult to develop potent and highly selective pure κ
opioid receptor antagonists. The first such compound developed was norꢀBNI (norꢀ
1
binaltorphimine) (Figure 1). In 2000, GNTI (5ꞌꢀguanidinonaltrindole) (Figure 1), a slightly more
2
potent κ opioid receptor antagonist, was developed. The naltrexoneꢀderived norBNI and GNTI
depend on the Nꢀcyclopropylmethyl group for their antagonistic properties. In 2001, we reported
the discovery of JDTic (Figure 1), a potent and selective κ opioid receptor antagonist with a
3ꢀ5
novel chemical structure.
JDTic displayed robust effectiveness in rodent models of
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depression, anxiety, stress induced cocaine relapse, nicotine withdrawal, and alcohol seeking,
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relapse, and withdrawal. Besides JDTic, PFꢀ4455242 and LY2456302 have been identified as
new classes of κ opioid receptor antagonists. However, both LY2456302 and PFꢀ4455242 have
lower potency and selectivity at the κ relative to the ꢁ and δ opioid receptors compared to JDTic,
norꢀBNI, and GNTI. Nevertheless, JDTic, LY2456302, and PFꢀ4455242 all proceeded through
10ꢀ13
preclinical development and were evaluated in phase 1 clinical studies.
The compound
LY2456302, now known as CERCꢀ501, is the only one still in clinical evaluation to the best of
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our knowledge. More recently, CYM51317 (structure not available) was reported as a new κ
1
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opioid receptor antagonist for migraine prevention.
We recently reported 1 (PDTic), a pure opioid receptor antagonist with a substantially simple
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tetrahydroisoquinoline moiety, as the lead compound for the design and development of novel
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class of potent and selective antagonists for the κ opioid receptor. In this study we report the
design, synthesis, and in vitro opioid receptor binding properties of compounds 3–39 and 41, 43,
4
5, and 47, which are structural analogues of 1 (structures for these compounds along with JDTic
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analogues 40, 42, 44, and 46 are given in Tables 1–7), using [ S]GTPγS binding assays. The
physiochemical properties of the more potent compounds were calculated to determine if the
compound(s) would be predicted to enter the brain and further pharmacokinetic studies in rats
were conducted on the most potent and selective κ opioid receptor antagonist identified to
determine if the compound did indeed penetrate the brain.
Results and Discussion
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2
3
Chemistry. The syntheses of the various analogues substituted at four positions R , R , R ,
4
and R in structure 2 (Figure 1) are outlined in Schemes 1–12. Synthesis of the azepanyl and
morpholinyl compounds 3 and 6 respectively, is shown in Scheme 1. LꢀValinol (48), prepared
1
6
according to
a
literature method,
was coupled with Bocꢀ7ꢀhydroxyꢀDꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxylic acid (Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH) using coupling agent N,N
ꞌꢀ
dicyclohexylcarbodiimide (DCC) to afford 49. The phenol in 49 was protected as the methyl
ether using trimethylsilyldiazomethane and the alcohol was oxidized with DessꢀMartin
periodinane to afford the aldehyde 50. Reductive amination with either azepane or morpholine
using sodium triacetoxyborohydride followed by concomitant methyl ether and Boc deprotection
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with boron tribromide in dichloromethane and subsequent treatment with ammonium hydroxide
afforded compounds 3 and 6.
As shown in Scheme 2, a variety of commercially available amines (pyrrolidine,
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azabicyclo[2.2.1]heptane,
diisobutylamine) were each subjected to coupling with NꢀBocꢀLꢀvaline (51), using Oꢀ
benzotriazoleꢀ1ꢀyl)ꢀ1,1,3,3ꢀtetramethyluroniumhexafluorophosphate (HBTU) and triethylamine
4ꢀmethylpiperazine,
diethylamine,
dipropylamine,
and
(
in acetonitrile, stirred at room temperature overnight, to provide the tertꢀbutyloxycarbonylꢀ
protected intermediate, which, upon treatment with hydrogen chloride in a solvent mixture of
dioxane and acetonitrile or trifluoroacetic acid in dichloromethane provided compounds 52a–f.
Amides 52a–f were reduced with borane dimethylsulfide in tetrahydrofuran to furnish diamines
5
3a–f. Subsequent coupling of the diamines 53a–f with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH using 1ꢀethylꢀ
3
ꢀ(3ꢀdimethylaminopropyl)carbodiimide (EDC), catalytic amounts of 1ꢀhydroxybenzotriazole
(HOBt) and triethylamine in dichloromethane followed by Bocꢀdeprotection (via treatment with
methanolic hydrochloric acid or hydrogen chloride in dioxane and acetonitrile) furnished final
compounds 4, 5 and 7–10.
The synthesis of a 2ꢀoxopiperidine derived compound 11, as outlined in Scheme 3,
commenced from Lꢀvalinol (48). The amine in 48 was protected as a benzylcarbamate (54) and
the alcohol converted to mesylate using methanesulfonyl chloride to yield 55. Compound 55 was
heated at reflux with 2ꢀhydroxypyridine in the presence of tetrabutylammonium bromide
1
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(TBAB), potassium carbonate, toluene and a catalytic amount of water to provide 56. Catalytic
hydrogenation of 56 using palladium on carbon catalyst yielded 57, which was subsequently
coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH, followed by the tertꢀbutyloxycarbonyl group
deprotection using hydrogen chloride in dioxane to provide compound 11.
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A plethora of substituted commercially available piperidines (58a–58c, 58f–g, 58i, 58k–n), as
well as some labꢀprepared known piperidines (58d–e, 58h, 58j), were employed for the synthesis
of substituted piperidine analogues 12–26 (Scheme 4). (Difluoromethyl)piperidine (58j) was
prepared in three steps from 4ꢀhydroxymethylpiperidine via an aldehyde that was subsequently
converted to 1ꢀNꢀBocꢀdifluoromethylpiperidine using diethylaminosulfur trifluoride (DAST) as
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previously reported. For the preparation of transꢀ3,4ꢀdimethylpiperidine ((±)ꢀ58e), the glutaric
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acid (±)ꢀ61 was prepared in three steps following a literature precedence, then was subjected to
ring closure by heating in a melt with urea at 180 °C for 3 h to provide 3,4ꢀdimethylpiperidineꢀ
2
,6ꢀdione as a mixture of the trans and cis isomers in a 2:1 ratio (Scheme 5). Recrystallization of
the mixture from ethyl acetate with hexanes provided the pure trans product (±)ꢀ62 that was
subsequently reduced using sodium borohydride and boron trifluoride etherate in tetrahydrofuran
to furnish (±)ꢀ58e (Scheme 5). The cisꢀ3,4ꢀdimethylpiperidine ((±)ꢀ58d) and 4ꢀethylpiperidine
(58h) were prepared from 3,4ꢀlutidine (63c) and 4ꢀethylpyridine (63d), respectively, via a threeꢀ
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step protocol reported in the literature, followed by subsequent catalytic hydrogenation to
provide (±)ꢀ58d and 58h (Scheme 6). Each of the piperidines (58a–58n) was coupled with Bocꢀ
Lꢀvaline (51) using HBTU in acetonitrile, followed by removal of the Bocꢀprotection using
either hydrogen chloride or trifluoroacetic acid to provide compounds 59a–59n (Scheme 4).
Reduction of these amides using borane dimethylsulfide gave the diamines 60a–60n. Some of
the 4ꢀcyano intermediate (60n) was subjected to an acid catalyzed conversion of the nitrile using
aqueous sulfuric acid, stirred at room temperature for 24 h, to furnish the 4ꢀcarboxamide (60o).
The diamine intermediates 60a–60o were next coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH using
EDC/HOBt followed the tertꢀbutyloxycarbonyl group deprotection using methanolic hydrogen
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chloride or hydrogen chloride in a dioxane acetonitrile mixture to yield the desired final
compounds 12–26, respectively (Scheme 4).
The pyridines used to prepare compounds 66b–66d, (±)ꢀ58d and 58h are shown in Scheme 6.
The tetrahydropyridines 66b–66d were prepared following a protocol similar to what has been
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previously reported from 4ꢀpicoline (63a), 3ꢀpicoline (63b) and 3,4ꢀlutidine (63c), respectively,
via the Nꢀbenzyl pyridinium salt, followed by reduction and subsequent cleavage of the benzyl
group to give 66b–66d. Intermediate 66a, as shown in Scheme 6, was commercially available.
Compounds 66a–66d were subjected to chemistry analogous to that described for the
piperidines: couplings with BocꢀLꢀvaline (51) and removal of the Bocꢀprotection to yield 67a–
67d, reduction with borane dimethylsulfide to give 68a–68d, subsequent coupling of those
products with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH, and a final Bocꢀdeprotection provided the final
compounds 27–30 (Scheme 7).
As shown in Scheme 8, the diastereomers 31–33 of 12 were synthesized using the different
enantiomers of the coupling intermediates. Coupling of 60a with Bocꢀ7ꢀhydroxyꢀLꢀTicꢀOH
yielded the diastereomer 31. On the other hand, the reactions starting with 4ꢀmethypiperidine
(58a) and NꢀBocꢀDꢀvaline (51) provided the intermediate 69 which was subsequently coupled
with either Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH or Bocꢀ7ꢀhydroxyꢀLꢀTicꢀOH to yield 32 and 33, in that
order.
Other analogues were synthesized where the isopropyl group, the phenol group or the
tetrahydroisoquinoline ring in 12 were changed or substituted by other groups (Schemes 9–12).
Commercially available Nꢀ(2ꢀaminoethyl)piperidine (70) was coupled with 7ꢀhydroxyꢀBocꢀDꢀ
TicꢀOH using dicyclohexylcarbodiimide (DCC) as the coupling agent in tetrahydrofuran,
followed by removal of the Bocꢀprotection group using methanolic hydrogen chloride to provide
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analogue 34 (Scheme 9). As shown in Scheme 10, NꢀBocꢀLꢀcyclopropylglycine was substituted
for BocꢀLꢀvaline for coupling with 58a to provide 71. Reduction of 71 using borane
dimethylsulfide in THF to give 72 followed by coupling with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH
provided 73a, which upon removal of the Bocꢀprotection using hydrogen chloride in methanol,
furnished the cyclopropyl analogue 35. Coupling 60a with BocꢀDꢀtyrosine in place of Bocꢀ7ꢀ
hydroxyꢀDꢀTicꢀOH using EDC/HOBt and triethylamine in dichloromethane, followed by a Bocꢀ
deprotection using hydrogen chloride in methanol, provided compound 36. Coupling of 6ꢀ
hydroxynapthaleneꢀ2ꢀcarboxylic acid with 60a in the presence of Nꢀethoxycarbonylꢀ2ꢀethoxyꢀ
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,2ꢀdihydroquinoline (EEDQ) in dimethylformamide as solvent, heated at 100 °C for 3 h,
furnished analogue 37. Bocꢀ7ꢀcarbamoylꢀDꢀTicꢀOH, prepared in three steps as previously
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reported, was coupled with diamine 60a to yield 73b which yielded 41 after the removal of the
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Bocꢀprotecting group. Similarly, Bocꢀ7ꢀfluoroꢀDꢀTicꢀOH, also previously reported, was
employed for the synthesis of 73d which upon Bocꢀdeprotection, furnished compound 45. The
phenolic hydroxy group in 73c was converted to the methyl ether upon treatment with
trimethylsilyl diazomethane followed by the removal of the Bocꢀprotecting group to provide
compound 43 (Scheme 10). For the synthesis of analogue 38, (Scheme 11), 6ꢀmethoxyꢀ1,2,3,4ꢀ
2
2
tetrahydronaphthaleneꢀ2ꢀcarboxylic acid (74a) was demethylated using hydrogen bromide in
acetic acid heated at reflux for 5 h to provide 74b, which was subsequently coupled with 60a
using (benzotriazoleꢀ1ꢀyloxy) tris(dimethylamino)phosphonium hexafluorophosphate (BOP) and
triethylamine in tetrahydrofuran stirred at room temperature overnight to provide 38 as a mixture
of diastereomers. Finally, as shown in Scheme 12, the reduced and N-methyl analogues of 12,
compounds 39 and 47, were both synthesized in one step from 12. Treatment of 12 in
tetrahydrofuran with borane dimethylsulfide heated at reflux overnight furnished the reduced
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analogue 39. On the other hand, treatment of 12 in dichloroethane with formalin followed by
sodium triacetoxyborohydride stirred at room temperature for 24 h yielded the Nꢀmethyl
analogue 47.
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Pharmacology Studies. As we recently reported, the structurally simple
tetrahydroisoquinoline analogue 1 had a K = 6.80 nM at κ, with K values of 144 and >3000 nM
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at the ꢁ and δ opioid receptors, respectively. Thus the compound was 21ꢀ and >441ꢀfold
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selective for the κ opioid receptor relative to the ꢁ and δ opioid receptors, respectively. Given
these encouraging results, we set out to examine the structure activity relationships of a variety
of 1 analogues. All synthesized compounds were evaluated for antagonist activity at the ꢁ, δ, and
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κ opioid receptors using our established assays that measure the ability of antagonists to inhibit
35
agonistꢀstimulated [ S]GTPγS binding in membranes prepared from CHO cells expressing
human opioid receptors. Concentration response curves of U69,593 (κ), DAMGO (ꢁ), or DPDPE
(δ) were run in the absence and presence of a single concentration of test compound. K values
e
were calculated with the equation K = [L]/(ER –1) where [L] is the concentration of test
e
compound and ER is the ratio of EC values in the presence and absence of test compound. K
e
5
0
values were considered valid when the ER was at least 4. Compounds were also evaluated for
agonist activity in the assays and none of our synthesized analogues displayed any activity at 10
ꢁ
M final concentration.
In order to determine the effect of changes in the piperidine ring size and type of ring on the κ
potency and selectivity of this new class of κ opioid receptor antagonists, we synthesized and
tested the larger ring size eight membered azepane, the smaller ring size, five membered
pyrrolidine analogues 3 and 4, respectively, as well as the bicyclic analogue 5 (Table 1). Similar
to 1, compounds 3, 4, and 5 were pure opioid antagonists. With a K = 48.5 nM at the κ opioid
e
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receptor, the pyrrolidine analogue 4 was seven times less potent at the κ opioid receptor than 1.
With a K = 17 nM at the κ opioid receptor, the azepane analogue 3 was only 2.5 times less
e
potent at the κ opioid receptor than 1, and with a K = 2.53 nM, the bicyclic analogue 5 was 2.7
e
1
1
1
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times more potent than 1. Compounds 4 and 3 had ꢁ/κ values of 14 and 41, respectively, and like
1
, were not very selective for the κ opioid receptor relative to the ꢁ opioid receptor. In contrast, 5
had a ꢁ/κ value of 296 and was highly selective for the κ relative to the ꢁ receptor. With a δ/κ
value of >1186, 5 was also highly selective for the κ receptor relative to the δ receptor. With δ/κ
values of >62 and >177, 4 and 3, respectively, were a little less selective for the κ opioid receptor
relative to the δ opioid receptor than 1. Changing the methylene group at the 4ꢀposition of the
piperidine ring of 1 with an oxygen or Nꢀmethyl group to give the morpholino and Nꢀ
methylpiperazine ring analogues, 6 and 7, respectively, resulted in large losses in potency for all
three receptors. Overall results from these changes to the piperidine ring of 1 suggest that the
piperidine analogue 1 is a better lead compound than the pyrrolidine and azepane analogues 4
and 3, respectively, as well as the morpholino and Nꢀmethylpiperazino analogues 6 and 7,
respectively.
In order to determine if the intact piperidine ring in 1 is needed for high potency at the κ opioid
receptor, the simple N,Nꢀdiethyl (8), N,Nꢀdipropyl (9), and N,Nꢀdiisobutyl (10) analogues were
synthesized and evaluated for their potency and selectivity as κ opioid receptor antagonists
(Table 1). Even though all three compounds were pure opioid antagonists, they were no better
than 1. The N,Nꢀdipropyl analogue 9, with a K = 14.5 nM at κ and ꢁ/κ and δ/κ values of 20.7
e
and >207, respectively, has the best κ potency and selectivity of the three analogues. However,
the results did not suggest that 9 would be a better lead compound than 1.
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6
In order to gain information concerning the need for the basic nature of the amino group in the
piperidine ring of 1, the 2ꢀoxopiperidine analogue 11 was synthesized and evaluated (Table 1).
The observation that 11 had a K of 61.5 nM at the κ opioid receptor suggests that the amino
e
0
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nature of 1 is required. However, low κ potency could be due to steric or other factors.
23,24
Since the importance that methyl groups can have in drug discovery is wellꢀdocumented
we investigated the opioid receptor efficacy of the monomethyl and dimethyl analogues 12–17.
Compounds 13–17 were tested as isomeric mixtures, where the incorporated piperidine was
either a racemate or, in the case of 17, purchased and used as a cis/trans mixture. These
methylatedꢀ1 analogues had K values at the κ opioid receptors ranging from 0.37 to 3.46 nM
e
(Table 2). Compound 12, with a K = 0.37 nM at the κ receptor and ꢁ/κ and δ/κ values of 646
e
and >8100, respectively, was the most potent and selective κ opioid receptor antagonist.
However, 15, which has a K = 1.26 nM at κ with ꢁ/κ and δ/κ values of 86 and 2381,
e
respectively, has good κ opioid receptor potency and selectivity. Compounds 16 and 17 with Ke
values at the κ opioid receptor of 2.3 and 3.46 nM, respectively, were also a little more potent
than 1. It is possible that one of the isomers of compounds 13–17 may be more potent than that
observed for the mixture of isomers.
The high κ antagonist potency and selectivity of 12 led us to investigate the opioid receptor
properties of compounds where the 4ꢀmethyl group was replaced by other substituents such as
the 4,4ꢀdimethyl 18, 4ꢀethyl 19, 4ꢀtrifluοromethyl 20, 4ꢀ(difluoromethyl) 21, 4ꢀmethoxy 22, 4ꢀ
(dimethylamino) 23, 4,4ꢀdifluoro 24, 4ꢀcyano 25, and the 4ꢀcarboxamide 26. These analogues of
35
1
2 were synthesized and tested in the [ S]GTPγS binding assay (Table 3) and found to have κ
opioid receptor K values ranging between 2.48 and 12.7 nM and thus were 7 to 34 times less
e
potent κ opioid receptor antagonists than the 4ꢀmethyl analogue 12. With ꢁ/κ values ranging
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from 14 to 51, none of the compounds were very selective for the κ relative to the ꢁ opioid
receptor. Since the δ/κ values for the compounds in Table 3 ranged from >236 to 1004, all of the
compounds are highly selective for the κ relative to the δ opioid receptor.
1
1
1
1
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To determine the effect on opioid antagonist potency by adding a 3,4ꢀdouble bond to 1, 12, and
1
5 or 16, we synthesized and evaluated corresponding analogues 27–30 (Table 4). The addition
of the 3,4ꢀdouble bond to 1 to give 27 results in a 6.4ꢀfold increase in κ antagonist potency: K =
e
6
.8 nM for 1 (Table 1) compared to a K = 1.07 nM for 27 (Table 4). The change also resulted in
e
a small increase in κ relative to ꢁ selectivity. In contrast, the addition of a 3,4ꢀdouble bond to 12
Table 2) to give 28 caused a 2.4ꢀfold loss in κ antagonist potency (K = 0.37 nM for 12
(
e
compared to K = 0.88 nM for 28) (Table 4). The change also caused a 20ꢀfold increase in ꢁ
e
antagonist potency (K = 239 nM for 12 compared to K = 11.8 nM for 28), thus reducing its
e
e
selectivity for the κ receptor relative to the ꢁ opioid receptor. Compound 29, which is the 3,4ꢀ
double bond analogue of 13 (Table 2) resulted in very little change in the κ opioid receptor
potency, K = 15.6 nM for 13 and 9.43 nM for 29. Both compounds have very low selectivity at
e
the κ relative to the ꢁ opioid receptor; however, both compounds were highly selective for the κ
relative to the δ opioid receptor. The most striking change resulted from adding a 3,4ꢀdouble
bond to 15 or 16, which both afford analogue 30. The K for the κ opioid receptor only changed
e
from 1.26 nM for 15 to K = 1.81 nM for 30. However, the K value at the ꢁ opioid receptor
e
e
changed from 108 nM for 15 to K = 1.09 nM for 30. Thus 15 (Table 2) and 30 (Table 4) have
e
about equal κ opioid receptor potency at both the ꢁ and κ opioid receptors. This results in 30 not
being selective for the κ relative to the ꢁ receptor. With a δ/κ value of 1066, 30 is highly
selective for both the ꢁ and the κ relative to the δ opioid receptor.
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Compound 12 has two asymmetric centers and thus three possible diastereomers (31–33). In
order to confirm 12 had the best overall properties, the three isomers 31–33, were synthesized
and tested. The three compounds had K values for the κ opioid receptor ranging between 9.29
e
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and 42.8 nM and thus were much less potent κ opioid receptor antagonists than 12. Compound
3
1, with a K = 9.29 nM and ꢁ/κ and δ/κ values of 103 and >323, respectively, was the most κ
e
potent and selective of the three diastereomers (Table 5), but 12 retained the preferred chirality.
In order to determine the importance of the isopropyl group on the efficacy of 1 and 12, the
analogues 34 and 35 were synthesized and evaluated. Replacement of the isopropyl groups in 1
with a hydrogen to give 34 changes its κ opioid receptor K value from 6.80 nM to a K = 113
e
e
nM, a 16.6ꢀfold loss in κ opioid receptor antagonist potency (Table 6). Replacement of the
isopropyl group in 12 with a similar sized cyclopropyl group results in a change at the κ opioid
receptor from a K = 0.37 nM for 12 (Table 2) to a K = 5.58 nM for 35, a 15ꢀfold loss in
e
e
antagonist potency (Table 6). This unexpected finding suggests that the isopropyl group may be
essential for the high κ potency and selectivity of 12. Replacing the 7ꢀhydoxylꢀDꢀTic group in 12
with the Dꢀtyrosine in 36 results in an over 1000ꢀfold loss in κ antagonist potency showing the
importance of the intact 7ꢀhydroxyꢀDꢀTic group to the κ opioid potency and selectivity of 12.
The need for the 7ꢀhydroxytetrahydroisoquinoline group in 12 was further substantiated by the
finding that analogues 37 and 38, which have a hydroxynaphthalene and 7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydronaphthalene group, respectively, replacing the 7ꢀhydroxytetrahydroisoquinoline group
in 12, had K values of 20.5 and 11.1 nM, respectively, at the κ opioid receptor (Table 6).
e
Analogue 39, which has the amide group reduced to a methyleneamino group, has a K = 17.2
e
nM, thus showing that the amide carbonyl group is also needed for the high κ potency of 12.
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In Table 7, the effect of replacing the phenolic hydroxyl group in 12 with other substituents
2
1
was determined and the results are compared to similar analogues of JDTic. Replacing the 7ꢀ
hydroxyl substituent in 12 with a carboxamido (41, K = 1.37 nM), methoxy (43, K = 25.6 nM),
e
e
1
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0
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and fluoro (45, K = 182 nM) substituent resulted in a 3.7ꢀ, 69ꢀ, and 492ꢀfold loss in κ opioid
e
receptor antagonist potency, respectively. In addition, the compounds were much less selective
for the κ relative to the ꢁ opioid receptor. A comparison of the results for 12 to the results for
similar substituted JDTic analogues are given in Table 7. While not as potent as JDTic,
compound 12, which like JDTic has a hydroxyl group in position 7, is a potent and selective κ
opioid receptor antagonist. The JDTic analogue 40, which has a carboxamido substituent in
21
position 7, is as potent as JDTic. However, compound 41, which has a carboxamido in place of
the hydroxyl in 12, is 3.7 times less potent than 12. Additionally, compound 42, which is the 7ꢀ
methoxy analogue of JDTic, is only 3ꢀfold less potent than JDTic and, like JDTic, is highly
2
5
selective for the κ opioid receptor relative to the ꢁ and δ opioid receptors. In contrast,
compound 43 (the methoxy analogue of 12) with a K = 25.6 nM at the κ opioid receptor, is 69
e
times less potent than 12 and is not very selective for κ relative to ꢁ. The 7ꢀfluoro analogue 44,
2
1
with a K = 2.20 nM, is 110ꢀfold less potent than JDTic. In comparison, the 7ꢀfluoro analogue
e
of 12, compound 45 with a K = 182 nM at the κ opioid receptor, is 492ꢀfold less potent than 12.
e
Thus, changes in the 7ꢀhydroxyl group of 12 are more sensitive to similar changes in JDTic and
2
1
thus do not follow the same SAR found in JDTic.
The difference between the SAR of the new tetrahydroisoquinoline analogues in this study and
the SAR of JDTic analogues is also shown by comparing the results obtained for 46 and 47,
which are the Nꢀmethyl analogues of JDTic and 12, respectively. The JDTic analogue 46, with a
26
K = 0.16 nM at the κ opioid receptor, is a potent κ opioid receptor antagonist. In contrast, 47
e
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has a K = 36.7 nM at the κ opioid receptor and is thus a much weaker κ opioid receptor
e
antagonist.
Table 8 shows a comparison of the calculated physiochemical properties of 12 and 15 to those
2
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of JDTic. Both 12 and 15 have TPSA (topological polar surface area) values of 64.60 Å
compared to 84.83 for JDTic. The cLogP values for 12 and 15 are 2.32 and 2.49, respectively,
compared to 3.60 for JDTic. The logBB values for 12 and 15 are –0.46 and –0.44, respectively,
compared to –0.57 for JDTic. The CNS MPO values for 12 and 15 are 4.5 and 4.1, respectively,
2 3,27
compared to a 3.1 value for JDTic. Compounds that have TPSA values less than 76 Å , cLogP
2
8
28,29
values in the range of 2–4, calculated logBB values less than –1,
and CNS MPO values
3
0
greater than 4, are predicted to penetrate the brain; therefore, both compounds 12 and 15 are
predicted to penetrate the brain. In addition, CNS penetration has been correlated with lower
3
1
molecular weights. The fact that molecular weights of 359.5 and 373.5 Daltons for 12 and 15
are 106 and 92 Daltons, respectively, less than JDTic, which is known to penetrate the brain,
further suggests that both 12 and 15 will penetrate the brain.
Pharmacokinetic Studies. The pharmacokinetics of 12 was assessed in plasma and brain
following a single dose to determine uptake into brain (Figure 2). In plasma, 12 reached a Cmax
of 333 ng/mL at 1 h after dosing, while in brain, a Cmax of 239 ng/mL was achieved at 4 h post
dose (Table 9). The halfꢀlife was determined to be 30.7 h in plasma and 57.2 h in brain. The ratio
of brain:plasma concentration rose between 1 and 72 h and then declined. Compound 12 crossed
the bloodꢀbrain barrier and persisted in plasma and brain for 168 h post dose. The AUClast was
approximately 10ꢀfold higher in brain compared with plasma and the clearance from the brain
was 11.2 times slower than from the plasma. The behavior of 12 was similar to that of JDTic,
which at a dose of 5 mg/kg in male rats had a half life of 28.4 h in plasma and 51.8 h in brain,
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and the AUClast was approximately 7ꢀfold higher in brain. Of four JDTic analogues
investigated previously, only RTIꢀ194 ((3R)ꢀ7ꢀhydroxyꢀNꢀ[(1S)ꢀ1ꢀ[[(3R,4R)ꢀ4ꢀ(3ꢀ
hydroxyphenyl)ꢀ3,4ꢀdimethylꢀ1ꢀpiperidinyl]methyl]ꢀ2ꢀmethylbutyl]ꢀ1,2,3,4ꢀtetrahydroꢀ3ꢀ
isoquinolineꢀcarboxamide) had a similar longer half life in brain, and AUClast was
1
1
1
1
1
1
1
1
1
1
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26
approximately10 fold higher in brain.
Conclusions
A SAR study directed towards the recently discovered new structural class of κ opioid receptor
antagonists based on lead structure 1 involving changes to the piperidine ring, absolute
stereochemistry, the 7ꢀhydroxy group on the tetrahydroisoquinoline and the isopropyl group, led
to the identification of the potent and selective κ opioid receptor antagonist 12. LogBB, CNS
MPO and molecular size predicted that 12 would penetrate the brain. Follow up pharmacokinetic
studies in rats showed that 12 did indeed readily penetrate the brain. These studies strongly
suggest that compound 12 should be considered for further development.
Experimental Section
Melting points were determined using a MELꢀTEMP II capillary melting point apparatus.
1
13
Nuclear magnetic resonance ( H NMR and C NMR) spectra were obtained on a Bruker Avance
DPXꢀ300 MHz NMR spectrometer. Chemical shifts are reported in parts per million (ppm) with
reference to internal solvent. Mass spectra (MS) were run on a PerkinꢀElmer Sciex API 150 EX
mass spectrometer equipped with ESI (turbospray) source. Elemental analyses were performed
by Atlantic Microlab Inc., Atlanta, GA. The purity of compounds (>95%) was established by
elemental analysis. Optical rotations were measured on an AutoPol III polarimeter, purchased
from Rudolf Research. Analytical thinꢀlayer chromatography (TLC) was carried out using EMD
silica gel 60 F254 TLC plates. TLC visualization was achieved with a UV lamp or in an iodine
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chamber. Flash column chromatography was done on a CombiFlash Rf system using ISCO
prepacked silica gel columns or using EM Science silica gel 60Å (230–400 mesh). Solvent
system: CMA80 (or DMA80) = 80:18:2 CHCl (or CH Cl ):CH OH:conc. NH OH. Unless
3
2
2
3
4
0
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otherwise stated, reagentꢀgrade chemicals were obtained from commercial sources and were used
without further purification. All moistureꢀ and airꢀsensitive reactions and reagent transfers were
carried out under dry nitrogen. See Supporting Information for the synthesis of all intermediate
compounds.
General Synthetic Procedures
General Method 1. Coupling of amines with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH. To a solution of
the amine (1.0 equiv) in CH Cl (30–50 mL) was added Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.1 equiv),
2
2
EDC (1.2 equiv), HOBt (0.11 equiv) and NEt (5.0–8.0 equiv). The mixture was stirred at room
3
temperature overnight. Saturated aqueous NaHCO (30 mL) was added to the mixture and the
3
organic product extracted with CH Cl (3 × 30 mL). The combined organic layers were dried
2
2
(
Na SO ), filtered through Celite and concentrated in vacuo. Purification of the residue on silica
2 4
gel eluted with CMA80 (or DMA80) in CH Cl to provide the desired Bocꢀprotected product that
2
2
was then subjected to General Method 2 for the cleavage of the Boc group. Alternatively, acid in
THF (0.1 M) was treated with DCC (1.2 eq.) and HOBt (1.1 eq). After 1 h at room temperature,
the amine (1.2 eq) was added. If the amine was a hydrochloride salt, NEt (3 eq) was also added.
3
After 12 h, the reaction mixture was filtered, concentrated, and the residue subjected to silica gel
chromatography to afford the desired amide.
General Method 2. Removal of Bocꢀprotection. 2a. The Bocꢀprotected compound in CH CN
3
was treated with HCl (4M in 1,4ꢀdioxane, 4 equiv.) and stirred at room temperature overnight.
The solvent was then removed in vacuo and the residue was neutralized with 1 N NaOH until the
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pH of 8–9 was obtained. Purification of the residue on silica gel and eluted with CMA80 (or
DMA80) in CH Cl provided the product. 2b. Alternatively, the Bocꢀprotected compound was
2
2
dissolved in CH OH (5 mL) then treated with 6 N aq HCl (5 mL) and stirred at room temperature
3
1
1
1
1
1
1
1
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2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
overnight. The solvent was evaporated, and the residue purified as above.
Preparation of the Hydrochloride salts. Hydrochloride salts were prepared by dissolving the
compound freebase in cold methanol, adding a slight excess of 2 N HCl in diethyl ether, then
evaporating to dryness under vacuum.
(3R)ꢀNꢀ[(1S)ꢀ1ꢀ(Azepanꢀ1ꢀylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (3) Dihydrochloride. Compound 50 (0.15 g, 0.4
mmol) and homopiperidine (110 mg, 1 mmol) in 1,2ꢀdichloroethane (3 mL) was treated with
sodium triacetoxyborohydride (200 mg, 0.9 mmol). After 12 h, the solution was washed with
saturated aqueous NaHCO , dried (Na SO ), and subjected to chromatography on silica gel
3
2
4
eluting with a gradient up to 10% CH OH in EtOAc to afford 99 mg (52%) of the Boc protected
3
intermediate. The intermediate was dissolved in CH Cl (10 mL) and treated with BBr (5 mL,
2
2
3
1
.0 M in CH Cl , 5 mmol) at –78 °C, then allowed to warm to room temperature overnight. The
2 2
solution was cooled to –78 °C, quenched with methanol, concentrated and then dissolved in
dilute aqueous NH OH (1:1). The aqueous solution was brought to a reflux, then cooled and the
4
solvent removed in vacuo. The residue obtained was purified bychromatography on silica gel
1
eluted with a gradient of 0–50% CMA80 in CH Cl to afford 3 freebase: H NMR (300 MHz,
2
2
CDCl ) δ 7.23 (d, J = 9.42 Hz, 1H), 6.85 (d, J = 8.29 Hz, 1H), 6.49 (d, J = 8.29 Hz, 1H), 6.43 (s,
3
1
H), 4.14 (td, J = 7.30, 14.41 Hz, 1H), 3.57–3.76 (m, 2H), 3.30 (dd, J = 5.09, 11.49 Hz, 1H),
.75–3.03 (m, 5H), 2.69 (d, J = 6.78 Hz, 2H), 2.35 (dd, J = 11.96, 15.92 Hz, 1H), 1.77–1.94 (m,
2
1
3
1H), 1.46–1.78 (m, 8H), 0.94 (dd, J = 1.79, 6.69 Hz, 6H); C NMR (75 MHz, CDCl ) δ 173.5,
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1
54.9, 137.2, 130.4, 125.1, 113.8, 112.2, 57.4, 56.8, 55.0, 50.6, 48.1, 31.4, 29.7, 27.4, 25.5, 19.1,
+
8.0; MS (ESI) m/z 360.4 (M + H) . The freebase 3 was converted to 25.5 mg (14% from 50) of
25
the dihydrochloride salt as a paleꢀyellow powder: mp 160–164 °C (fusion), [α]D +65.5° (c
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
0
.165, CH OH). Anal. (C H Cl N O •1.5 H O) C, H, N.
3
21 35
2
3
2
2
(3R)ꢀ7ꢀHydroxyꢀNꢀ[(1S)ꢀ2ꢀmethylꢀ1ꢀ(pyrrolidinꢀ1ꢀylmethyl)propyl]ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (4) Dihydrochloride. Compound 53a (1.03 g, 6.02
mmol) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.77 g, 6.02 mmol) following the protocol
described in General Method 1 to provide the Boc protected product Bocꢀ4 (1.43 g, 55% yield).
1
H NMR (300 MHz, CDCl ) δ 7.81 (br. s., 1H), 6.91 (d, J = 8.10 Hz, 1H), 6.48–6.70 (m, 2H),
3
5.94–6.31 (m, 1H), 4.58–4.87 (m, 1H), 4.31–4.57 (m, 2H), 3.56–3.81 (m, 1H), 3.07–3.31 (m,
2
H), 2.91 (d, J = 10.17 Hz, 1H), 2.08–2.35 (m, 4H), 1.71–1.91 (m, 1H), 1.57 (br. s., 4H), 1.38–
13
1
.50 (m, 9H), 1.07–1.34 (m, 1H), 0.77 (dd, J = 6.69, 13.28 Hz, 6H); C NMR (75 MHz, CDCl )
3
δ 171.8, 155.5, 134.0, 129.0, 123.8, 114.7, 113.1, 81.3, 60.4, 57.9, 56.5, 54.0, 53.1, 44.9, 44.5,
+
3
0.9, 30.2, 28.3, 23.4, 18.8, 17.5; MS (ESI) m/z 432.3 (M + H) . Bocꢀ4 (1.43 g, 3.32 mmol) was
subjected to Bocꢀcleavage according to General Method 2b to provide amine 4 (839 mg, 76%
1
yield). H NMR (300 MHz, CDCl ) δ 7.14 (d, J = 10.17 Hz, 1H), 6.78 (d, J = 8.10 Hz, 1H),
3
6
.22–6.39 (m, 2H), 5.75–6.17 (m, 1H), 4.16 (t, J = 10.55 Hz, 1H), 3.59–3.73 (m, 1H), 3.47–3.58
m, 1H), 3.20 (dd, J = 5.27, 11.68 Hz, 1H), 2.95 (t, J = 12.15 Hz, 1H), 2.84 (dd, J = 5.09, 16.58
Hz, 1H), 2.72 (br. s., 2H), 2.61 (br. s., 2H), 2.27 (dd, J = 2.64, 12.43 Hz, 1H), 2.01–2.15 (m, 1H),
(
1
3
1.70–1.92 (m, 5H), 0.75–1.02 (m, 6H); C NMR (75 MHz, CDCl ) δ 173.4, 155.1, 137.6, 130.8,
3
1
25.0, 113.2, 112.0, 57.2, 56.5, 54.0, 51.8, 48.5, 32.0, 28.9, 23.1, 19.0, 18.0; MS (ESI) m/z 332.5
+
25
D
(M + H) . A white solid was obtained of the dihydrochloride salt of 4. mp 148 °C (dec.); [α]
=
+67.3° (c 1.1, CH OH). Anal. (C H Cl N O •H O) C, H, N. To make a fumarate salt, 4 (376.6
3
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mg, 1.14 mmol) was dissolved in chloroform (2 mL) in a vial and treated with fumaric acid in
MeOH (2.0 equiv. 3.5 mL, 0.65 M in MeOH) and allowed to stand in a refrigerator overnight.
The excess solvent was then removed under reduced pressure and the residue salt was
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
redissolved in minimal amount of MeOH. The fumarate salt was recrystallized from MeOH
25
using diethyl ether to provide 329 mg of 4•2C H O as a beige solid; mp 152 °C (dec.); [α]
D
=
4
4
4
+
65.0° (c 1.1, CH OH). Anal. (C H N O •1.25 H O) C, H, N.
3 27 37 3 10 2
(3R)ꢀNꢀ[(1S)ꢀ1ꢀ(7ꢀAzabicyclo[2.2.1]heptꢀ7ꢀylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (5) Dihydrochloride. solution of
A
dicyclohexylcarbodiimide (DCC) (120 mg, 0.58 mmol) in THF (2 mL) was treated with a THF
(3 mL) solution of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH (150 mg, 0.51
mmol)and stirred at room temperature for 1 h. Amine 53b (140 mg, 0.77 mmol) and NEt (0.2
3
mL, 1.4 mmol) were added to the suspension and stirred for an additional 12 h at room
temperature. . The solids were removed by filtration and the filtrate concentrated under reduced
pressure. The residue obtained was purified by chromatography on silica gel eluted with a
gradient of 0–50% DMA80 in CH Cl . The fractions containing the product were concentrated
2
2
and the residue dissolved in CH OH (5 mL) and treated with 6 N HCl aq (5 mL). After 12 h, the
3
solvent was removed in vacuo, and the residue partitioned between CH Cl and 7 M aq NH OH.
2
2
4
The organic layer was dried (Na SO ) and concentrated. The resulting residue was subjected to
2
4
chromatography on silica gel eluting with a gradient of 0–75% DMA80 in CH Cl to afford 36.4
2
2
1
mg (10%) of the freebase 5: H NMR (300 MHz, CDCl ) δ 7.11 (d, J = 9.61 Hz, 1H), 6.78 (d, J
3
=
8.10 Hz, 1H), 6.44 (dd, J = 2.35, 8.19 Hz, 1H), 6.32 (d, J = 2.26 Hz, 1H), 3.86–4.00 (m, 1H),
3
.36–3.68 (m, 4H), 3.08 (dd, J = 5.09, 11.68 Hz, 1H), 2.81 (dd, J = 4.90, 16.39 Hz, 1H), 2.51–
2.71 (m, 1H), 2.40 (dd, J = 2.54, 12.90 Hz, 1H), 2.13–2.30 (m, 1H), 1.63–1.91 (m, 5H), 1.23–
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5
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6
13
1
1
.44 (m, 4H), 0.72–0.94 (m, 6H); C NMR (75 MHz, CDCl ) δ 173.4, 155.2, 137.4, 130.6,
3
25.0, 113.8, 112.1, 59.8, 56.7, 52.2, 48.4, 48.0, 31.7, 29.7, 28.2, 18.8, 18.3. The freebase was
+
converted into a pale yellow powder as the dihydrochloride salt: MS (ESI) m/z 358.4 (M + H) ;
25
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
m.p. 194–198 °C (fusion); [α]D = +72° (c 0.10, CH OH). Anal. (C H Cl N O •1.5 H O) C, H,
3
21 33
2
3
2
2
N.
(
3R)ꢀ7ꢀHydroxyꢀNꢀ[(1S)ꢀ2ꢀmethylꢀ1ꢀ(morpholinꢀ4ꢀylmethyl)propyl]ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (6) Dihydrochloride. A solution of 50 (0.15 g, 0.4
mmol) in dichloroethane (3 mL) was treated with morpholine (0.09 mL, 1 mmol) then sodium
triacetoxyborohydride (200 mg, 0.9 mmol). After 12 h, the solution was washed with saturated
aqueous NaHCO , dried (Na SO ), and subjected to chromatography on silica gel eluting with
3
2
4
EtOAc to afford 100 mg (54%) of the Bocꢀprotected intermediate. The Boc intermediate was
dissolved in CH Cl (10 mL), cooled to –78 °C, treated with BBr (5 mL, 1.0 M in CH Cl , 5
2
2
3
2
2
mmol) and allowed to warm to room temperature overnight. The solution was cooled to –78 °C,
quenched with methanol, concentrated and then dissolved in 50% dilute aqueous NH OH. The
4
aqueous solution was brought to a reflux, then cooled and concentrated. The residue was
subjected to chromatography on silica gel eluting with a gradient of 0–50% CMA80 in CH Cl to
2
2
1
afford 6. H NMR (300 MHz, CDCl ) δ 7.10 (d, J = 9.80 Hz, 1H), 6.91 (d, J = 8.29 Hz, 1H),
3
6
.60 (dd, J = 2.45, 8.29 Hz, 1H), 6.45 (d, J = 2.07 Hz, 1H), 4.11–4.18 (m, 1H), 3.63–3.78 (m,
H), 3.37 (dd, J = 5.18, 10.83 Hz, 1H), 2.98 (dd, J = 5.09, 16.39 Hz, 1H), 2.47–2.68 (m, 4H),
6
13
2.29–2.43 (m, 3H), 1.85 (dd, J = 6.78, 11.87 Hz, 1H), 0.89–0.96 (m, 6H); C NMR (75 MHz,
CDCl ) δ 173.5, 154.7, 137.1, 130.4, 125.3, 114.0, 112.2, 66.6, 60.5, 56.7, 53.8, 49.7, 47.8, 31.1,
3
+
2
9.8, 19.2, 17.8; MS (ESI) m/z 348.3 (M + H) . The freebase was converted to 42.2 mg (44%) of
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the dihydrochloride salt as a white powder: mp 186–190 °C (fusion), [α]D +62° (c 0.16,
CH OH). Anal. (C H Cl N O •1.5 H O) C, H, N.
3
19 31
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3
3
2
(3R)ꢀ7ꢀHydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[(4ꢀmethylpiperizinꢀ1ꢀyl)methyl]propyl}ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (7) Trihydrochloride. Diamine 53c (937 mg, 5.06
mmol) and Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.6 g, 5.31 mmol) in a solvent mixture of THF (4 mL)
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
and CH CN were coupled using HBTU (2.32 g, 6.07 mmol) (instead of EDC/HOBt) and
3
triethylamine (2.8 mL, 20.5 mmol) to provide Bocꢀprotected product Bocꢀ7 (1.82 g mg, 78%
1
yield). H NMR (300 MHz, CDCl ) δ 6.95 (d, J = 8.1 Hz, 1H), 6.67 (d, J = 8.3 Hz, 1H), 6.65 (s,
3
1
H), 5.97–6.41 (m, 1H), 4.71–4.80 (br. s., 1H), 4.40–4.58 (m, 2H), 3.83 (br. s., 1H), 3.18–3.24
(dd, J = 2.5, 15.3 Hz, 1H), 2.95–3.02 (m, 1H), 2.74–2.82 (m, 2H), 2.20–2.25 (m, 2H), 1.85–1.92
(
m, 2H), 1.51 (s, 9H), 1.40–1.60 (m, 3H), 1.12–1.33 (m, 6H), 0.85–0.95 (m, 3H), 0.45–0.59 (m,
1
3
3
H); C NMR (75 MHz, CDCl ) δ 171.8, 155.2, 134.0, 129.1, 123.9, 114.7, 113.2, 81.1, 65.8,
3
59.5, 57.9, 54.3, 53.8, 51.2, 45.1, 34.1, 31.4, 30.8, 30.5, 29.6, 28.4 (3Cs), 21.8, 18.5, 16.6; MS
+
(
ESI) m/z 460.4 (M + H) . Bocꢀ7 (689 mg, 1.5 mmol) was treated according to the General
Method 2b for removal of the Bocꢀprotection to provide 348 mg (64%) of the freebase amine 7:
1
H NMR (300 MHz, CD OD) δ 6.97 (d, J = 8.3 Hz, 1H), 6.66 (dd, J = 8.4, 2.4 Hz, 1H), 6.56 (d,
3
J = 2.5 Hz, 1H), 4.07–4.16 (m, 2H), 3.95–4.01 (m, 1H), 3.78–3.82 (dd, J = 5.0, 4.4 Hz, 1H),
2
0
.87–3.09 (m, 2H), 2.60–2.80 (m, 6H), 2.48 (s, 3H), 2.45–2.57 (m, 3H), 1.78–1.87 (m, 1H),
1
3
.93–0.96 (m, 6H); C NMR (75 MHz, CD OD) δ 174.0, 157.1, 135.4, 131.1, 124.7, 115.6,
3
113.5, 60.7, 58.4, 57.7, 55.4, 52.8, 52.6, 47.1, 45.1, 32.2, 31.8, 20.2, 18.5, 18.3; MS (ESI) m/z
+
25
3
60.3 (M + H) . A white solid was obtained as the trihydrochloride salt of 7: mp >240 °C; [α]
D
=
+71.2° (c 1.1, CH OH) Anal. (C H Cl N O •1.75 H O) C, H, N.
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(
3R)ꢀNꢀ{(1S)ꢀ1ꢀ[(4,4ꢀDiethylamino)methyl]ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (8) Dihydrochloride. Diamine 53d (336 mg, 1.45
mmol) in CH Cl (30 mL) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (426 mg, 1.45 mmol)
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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1
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3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
following the protocol described in General Method 1 to provide 200 mg (32%) of the product
1
Bocꢀ8: H NMR (300 MHz, CDCl ) δ 7.78 (br. s., 1H), 6.94 (d, J = 8.2 Hz, 1H), 6.66 (dd, J =
3
2
.6, 8.3 Hz, 1H), 6.61 (s, 1H), 6.25–6.40 (m, 1H), 4.70–4.85 (m, 1H), 4.43–4.55 (m, 2H), 3.77
(
br s, 1H), 3.17–3.24 (dd, J = 3.8, 15.6 Hz, 1H), 2.95–3.02 (dd, J = 6.2, 16.2 Hz, 1H), 2.51–2.78
(
m, 2H), 2.25–2.50 (m, 3H), 1.83–2.12 (m, 2H), 2.05 (s, 1H), 1.49 (s, 9H), 1.18–1.35 (m, 4H),
1
3
0
.78–1.07 (m, 11H); C NMR (75 MHz, CDCl ) δ 171.8, 155.6, 134.1, 129.1, 124.2, 114.6,
3
113.2, 81.5, 56.7, 52.9, 51.7, 46.5, 44.9, 30.9, 29.4, 28.4 (3Cs), 21.0, 18.8, 17.4, 14.1; MS (ESI)
+
m/z 434.5 (M + H) . A solution of Bocꢀ8 (517 mg, 1.19 mmol) in CH CN (20 mL) was subjected
3
1
to Boc cleavage following the General Method 2a to provide the freebase 8: H NMR (300 MHz,
CD OD) δ 6.98 (d, J = 8.6 Hz, 1H), 6.68 (dd, J = 8.4, 2.6 Hz, 1H), 6.57 (d, J = 2.6 Hz, 1H),
3
4
.06–4.21 (m, 2H), 4.11 (s, 1H), 3.83–3.89 (dd, J = 5.1, 11.3 Hz, 1H), 3.10–3.33 (m, 5H), 3.36
13
(
s, 1H), 2.84–3.07 (m, 2H), 1.84–1.95 (m, 1H), 1.28–1.34 (m, 5H), 0.91–1.05 (m, 6H); C NMR
(
75 MHz, CD OD) δ 174.5, 157.2, 134.7, 131.2, 124.7, 115.7, 113.5, 58.1, 55.4, 51.2, 47.3, 32.6,
3
+
3
1.3, 20.0, 18.5, 9.2; MS (ESI) m/z 334.5 (M + H) . The freebase was converted into a white
25
solid as the dihydrochloride salt (332 mg, 84%): mp 152–155 °C; [α]D = +70.5° (c 1.1,
CH OH). Anal. (C H Cl N O •1.25 H O) C, H, N.
3
22 37
2
3
2
2
(3R)ꢀN-{(1S)ꢀ1ꢀ[(Dipropylamino)methyl]ꢀ2ꢀmethylpropyl}ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (9) Dihydrochloride. To a solution of 53e (544 mg,
2
.1 mmol) in CH Cl (45 mL) was added Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (677 mg, 2.31 mmol), EDC
2 2
(483 mg, 2.52 mmol), HOBt (35.3 mg, 0.23 mmol) and NEt (0.7 mL, 5.04 mmol) and reacted as
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described in General Method 1 to provide Bocꢀ9 (864.8 mg, 89% yield): H NMR (300 MHz,
CDCl ) δ 6.95 (d, J = 8.7 Hz, 1H), 6.67 (d, J = 9.5 Hz, 1H), 6.59 (s, 1H), 5.90–6.00 (m, 1H),
3
4.38–4.67 (m, 3H), 3.69 (br. s., 1H), 3.47 (s, 1H), 3.16 (d, J = 11.4 Hz, 1H), 2.94–3.02 (dd, J =
1
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0
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8
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0
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6
.7, 4.7 Hz, 1H), 1.94–2.40 (m, 7H), 1.50 (s, 9H), 1.26–1.34 (m, 4H), 0.76–0.85 (m, 12H); C
NMR (75 MHz, CDCl ) δ 172.0, 155.6, 134.2, 129.0, 124.1, 123.9, 114.7, 113.1, 81.5, 56.7,
3
5
4
5
6
5.9, 54.2, 51.9, 50.3, 44.9, 31.1, 30.0, 28.9, 28.4, 28.3, 19.6, 18.8, 16.9, 11.8; MS (ESI) m/z
+
62.8 (M + H) . Bocꢀ9 was subjected to Boc cleavage following General Method 2a to provide
1
33 mg (79% yield) of the freebase 9: H NMR (300 MHz, CD OD) δ 6.91 (d, J = 8.1 Hz, 1H),
3
.61 (dd, J = 8.3, 2.9 Hz, 1H), 6.50 (d, J = 2.9 Hz, 1H),3.90–4.30 (m, 1H), 3.92 (d, J = 2.2 Hz,
1H), 3.53–3.58 (dd, J = 10.7, 4.5 Hz, 1H), 3.37 (s, 1H), 2.92–2.99 (dd, J = 5.2, 3.4 Hz, 1H),
2
1
.74–2.82 (m, 1H), 2.33–2.64 (m, 6H), 1.91–1.97 (m, 1H), 1.43–1.56 (m, 4H), 0.88–1.04 (m,
1
3
2H); C NMR (75 MHz, CD OD) δ 175.4, 156.9, 137.3, 130.9, 125.6, 115.1, 113.3, 58.3, 57.4,
3
57.2, 56.0, 53.0, 48.1, 32.3, 31.6, 21.0, 20.8, 20.3, 19.3, 17.7, 12.3; MS (ESI) m/z 362.4 (M +
+
25
D
H) . A white solid was obtained as the dihydrochloride salt of 9: mp 160 °C (sublime); [α]
=
+
55.1° (c 1.1, CH OH). Anal. (C H Cl N O •2 H O) C, H, N.
3 21 37 2 3 2 2
(
3R)ꢀNꢀ{(1S)ꢀ1ꢀ{[Bis(2ꢀmethylpropyl)amino]methyl}ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (10) Dihydrochloride. The diamine 53f (865 mg, 2.82
mmol) in CH Cl (30 mL) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (803 mg, 2.74 mmol)
2
2
1
following the protocol described in General Method 1 to provide 537 mg (40%) of Bocꢀ10. H
NMR (300 MHz, CDCl ) δ 7.78 (br. s., 1H), 6.94 (d, J = 8.2 Hz, 1H), 6.66 (dd, J = 2.6, 8.3 Hz,
3
1
3
H), 6.61 (s, 1H), 6.25–6.40 (m, 1H), 4.70–4.85 (m, 1H), 4.43–4.55 (m, 2H), 3.77 (br. s., 1H),
.17–3.24 (dd, J = 3.8, 15.6 Hz, 1H), 2.95–3.02 (dd, J = 6.2, 16.2 Hz, 1H), 2.51–2.78 (m, 2H),
2.25–2.50 (m, 3H), 2.05 (s, 1H), 1.90–2.18 (m, 6H), 1.50 (s, 9H), 1.46–1.70 (m, 3H), 0.70–0.96
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13
(
m, 18H); C NMR (75 MHz, CDCl ) δ 171.8, 155.6, 134.3, 129.0, 124.3, 114.8, 113.1, 81.5,
3
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4.1, 56.9, 56.6, 52.0, 44.9, 31.4, 29.4, 28.4 (3Cs), 28.0, 26.4, 26.3, 20.9, 20.8, 19.6, 15.7; MS
+
(ESI) m/z 490.7 (M + H) . Bocꢀ10 (655 mg, 1.34 mmol) in CH CN (20 mL) was subjected to
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Boc cleavage following the General Method 2a afford the freebase 10: H NMR (300 MHz,
CD OD) δ 6.93 (d, J = 8.6 Hz, 1H), 6.61 (dd, J = 2.8, 8.4 Hz, 1H), 6.51 (d, J = 2.1 Hz, 1H),
3
3
1
2
.96–4.01 (m, 2H), 3.95 (s, 1H), 3.53–3.59 (dd, J = 4.7, 11.5 Hz, 1H), 2.94–3.01 (dd, J = 4.3,
5.8 Hz, 1H), 2.72–2.81 (dd, J = 10.5, 15.8 Hz, 1H), 2.48–2.55 (dd, J = 7.6, 13.4 Hz, 1H), 2.23–
13
.30 (dd, J = 7.2, 13.3 Hz, 1H), 2.05–2.20 (m, 5H), 1.67–1.80 (m, 2H), 0.89–1.05 (m, 18H); C
NMR (75 MHz, CD OD) δ 175.1, 156.9, 137.1, 130.8, 125.5, 115.1, 113.2, 58.9, 58.2, 53.3,
3
+
47.9, 32.4, 30.7, 27.7, 21.5, 20.5, 16.8; MS (ESI) m/z 374.5 (M + H) . The freebase was
converted into a white solid as the dihydrochloride salt (332 mg, 72% yield): mp 178–180 °C;
2
5
[
α]D = +75.5° (c 1.1, CH OH). Anal. (C H Cl N O •1.5 H O) C, H, N.
3 22 37 2 3 2 2
(3R)ꢀ7ꢀHydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[(2ꢀoxopiperidinꢀ1ꢀyl)methyl]propyl}ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (11) Hydrochloride. Compound 57 (400 mg, 2.2
mmol) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (638 mg, 2.2 mmol) following the protocol
1
described in General Method 1 to provide Bocꢀ11 (389 mg, 39%): H NMR (300 MHz, CDCl ) δ
3
6
2
1
.86–7.15 (m, 1H), 6.50–6.77 (m, 2H), 6.34 (br. s., 1H), 4.73 (br. s., 1H), 4.55 (d, J = 16.58 Hz,
H), 4.25–4.48 (m, 1H), 3.73–4.02 (m, 1H), 3.25 (br. s., 1H), 2.87–3.21 (m, 4H), 2.67 (br. s.,
1
3
H), 2.11–2.33 (m, 2H), 1.62–1.84 (m, 2H), 1.40–1.62 (m, 12H), 0.86 (br. s., 6H); C NMR (75
MHz, CDCl ) δ 172.1, 171.4, 155.9, 134.3, 128.8, 123.8, 114.4, 113.0, 80.9, 56.6, 54.9, 51.8,
3
4
7.6, 45.0, 44.3, 42.1, 31.8, 30.6, 30.3, 28.3, 22.7, 20.8, 19.0, 17.7; MS (ESI) m/z 460.3 (M +
+
H) . Bocꢀ11 (370 mg, 0.81 mmol) was subjected to Bocꢀcleavage according to General Method
1
2a to provide the amine 11 (245 mg, 85%): H NMR (300 MHz, CDCl ) δ 7.09–7.38 (m, 1H),
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.85 (d, J = 8.29 Hz, 1H), 6.54–6.71 (m, 1H), 6.40–6.53 (m, 1H), 4.21–4.40 (m, 1H), 3.99–4.19
(m, 1H), 3.48–3.79 (m, 3H), 3.34 (dd, J = 4.52, 11.30 Hz, 1H), 2.88–3.19 (m, 2H), 2.65 (dd, J =
2.83, 13.37 Hz, 1H), 2.20–2.53 (m, 3H), 1.38–1.89 (m, 5H), 1.13–1.34 (m, 1H), 0.70–1.01 (m,
1
3
1
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9
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0
6
5
H); C NMR (75 MHz, CDCl ) δ 173.6, 171.4, 155.3, 136.8, 130.0, 124.7, 113.9, 112.1, 56.9,
3
+
1.4, 48.7, 47.8, 44.8, 41.8, 32.2, 30.8, 22.9, 20.9, 19.4, 18.3; MS (ESI) m/z 360.4 (M + H) . A
2
5
white solid was obtained as the hydrochloride salt of 11: mp 154–157 °C (dec.); [α]D = +68.8°
c 1.1, CH OH). Anal. (C H ClN O •0.5 H O) C, H, N.
(
3
20 30
3
3
2
(3R)ꢀ7ꢀHydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[(4ꢀmethylpiperidinꢀ1ꢀyl)methyl]propyl}ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (12) Dihydrochloride. Compound 60a (908 mg, 3.53
mmol) in CH Cl (50 mL), Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.14 g, 3.88 mmol), EDC (812 mg, 4.23
2
2
mmol), HOBt (59 mg, 0.39 mmol) and NEt (1.2 mL, 8.48 mmol) were reacted as described in
3
1
General Method 1 to provide 1.1 g (68%) of the Bocꢀ12. H NMR (300 MHz, CDCl ) δ 6.96 (d,
3
J = 9.2 Hz, 1H), 6.65 (d, J = 9.7 Hz, 1H), 5.90–6.00 (m, 1H), 6.60 (s, 1H), 4.41–4.58 (m, 2H),
3
2
0
1
1
.80 (br s, 1H), 3.45 (s, 1H), 3.17–3.29 (m, 1H), 2.95–3.02 (d, J = 11.4 Hz, 1H), 2.40–2.63 (m,
H), 2.03–2.25 (m, 2H) 1.70–1.87 (m, 3H), 1.50 (s, 9H), 1.40–1.60 (m, 3H), 1.02–1.30 (m, 3H),
1
3
.78–0.88 (m, 9H); C NMR (75 MHz, CDCl ) δ 171.6, 155.6, 134.1, 129.1, 123.9, 114.7,
3
13.1, 81.4, 59.3, 56.9, 56.5, 54.3, 53.5, 51.3, 45.1, 44.8, 34.2, 34.0, 30.5, 30.2, 28.4 (3Cs), 21.8,
+
8.9, 17.4; MS (ESI) m/z 460.2 (M + H) . Bocꢀ12 (1.1 g, 2.3 mmol) in CH CN (20 mL) was
3
subjected to Bocꢀcleavage using General Method 2a to provide compound 12 (594 mg, 72%) as
1
the freebase: H NMR (300 MHz, CD OD) δ 6.96 (d, J = 8.7 Hz, 1H), 6.68 (dd, J = 8.4, 2.9 Hz,
3
4
.16–4.21 (m, 1H), 1H), 6.58 (d, J = 2.5 Hz, 1H), 4.09 (d, J = 3.3 Hz, 1H), 3.96–4.06 (m, 1H),
.83–3.89 (dd, J = 5.6, 5.2 Hz, 1H), 3.58–3.64 (m, 1H), 3.37 (s, 1H) 3.31–3.39 (m, 2H), 3.10–
3
3.17 (m, 2H), 3.00–3.07 (m, 1H), 2.86–2.96 (m, 2H), 2.71–2.79 (m, 1H), 1.96 (s, 1H), 1.78–1.91
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13
(
m, 3H), 1.39–1.63 (m, 3H), 0.97–1.00 (m, 9H); C NMR (75 MHz, CD OD) δ 174.5, 157.2,
3
1
35.0, 131.2, 124.5, 115.7, 113.5, 60.7, 58.1, 55.5, 53.5, 51.1, 50.0, 47.5, 32.6, 32.5, 31.5, 30.1,
+
21.6, 20.0, 18.5; MS (ESI) m/z 360.3 (M + H) . A white solid was obtained as the
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dihydrochloride salt of 12: mp 180 °C (dec.); [α]D = +65° (c 1.1, CH OH). Anal.
3
(C H Cl N O •1.25 H O) C, H, N.
21 35 2 3 2 2
(
3R)ꢀ7ꢀHydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[((3RS)ꢀ3ꢀmethylpiperidinꢀ1ꢀyl)methyl]propyl}ꢀ
1
,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxamide (13) Dihydrochloride. Diamine 60b (839 mg,
4
.55 mmol) and Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.6 g, 5.46 mmol) were coupled according to the
General Method 1 to provide desired product Bocꢀ13 (1.6 g, 59%) as a mixture of diastereomers:
1
H NMR (300 MHz, CDCl ) δ 6.82–7.18 (m, 2H), 6.51–6.82 (m, 3H), 5.85–6.40 (m, 1H), 4.68
3
(
br. s., 1H), 4.50–4.64 (m, 1H), 4.29–4.49 (m, 1H), 3.65–3.92 (m, 1H), 3.08–3.34 (m, 2H), 2.81–
3
.08 (m, 1H), 2.58 (br. s., 2H), 1.95–2.30 (m, 2H), 1.85 (d, J = 15.45 Hz, 1H), 1.69 (d, J = 9.98
1
3
Hz, 1H), 1.50 (s., 9H), 1.34–1.61 (m, 4H), 0.67–0.97 (m, 9H); C NMR (75 MHz, CDCl ) δ
3
1
3
71.6, 155.5, 134.1, 129.1, 124.0, 114.7, 113.0, 81.1, 62.6, 60.4, 59.3, 54.6, 53.2, 51.4, 44.9,
+
2.8, 30.7, 30.1, 28.4, 28.3 (3 C’s), 25.3, 19.6, 18.8, 17.5; MS (ESI) m/z 460.5 (M + H) . Bocꢀ13
(
1.24 g, 2.69 mmol) was treated as described in General Method 2a to remove the Bocꢀprotection
and 626 mg (65% yield) of the freebase compound 13 was obtained as a mixture of
1
diastereomers: H NMR (300 MHz, CD OD) δ 6.86–6.95 (m, 1H), 6.61 (dd, J = 2.45, 8.10 Hz,
3
1
H), 6.49 (d, J = 2.26 Hz, 1H), 3.97–4.09 (m, 1H), 3.83–3.97 (m, 2H), 3.44–3.67 (m, 3H), 2.87–
3.09 (m, 2H), 2.64–2.87 (m, 2H), 2.32–2.61 (m, 2H), 1.75–2.00 (m, 2H), 1.45–1.75 (m, 4H),
13
0
1
.77–1.06 (m, 9H); C NMR (75 MHz, CD OD) δ 175.3, 156.8, 137.4, 130.9, 125.6, 115.0,
3
13.3, 66.9, 63.8, 62.7, 61.7, 58.2, 55.8, 54.5, 52.3, 34.0, 32.3, 26.4, 20.0, 18.5, 18.0; MS (ESI)
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+
m/z 360.4 (M + H) . A white solid was obtained as the dihydrochloride salt of 13: mp 178 °C
2
2
(
dec.); [α]D = +75.5° (c 1.1, CH OH). Anal. (C H Cl N O •H O) C, H, N.
3 21 35 2 3 2 2
(3R)ꢀ7ꢀHydroxyꢀNꢀ{(1S)ꢀ2ꢀmethylꢀ1ꢀ[((2RS)ꢀ2ꢀmethylpiperidinꢀ1ꢀyl)methyl]propyl}ꢀ
,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxamide (14) Dihydrochloride. The diamine 60c (1.37
1
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0
1
g, 5.34 mmol) and Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.57 g, 5.34 mmol) were coupled according to the
General Method 1 to provide desired product Bocꢀ14 (1.1 g, 44%) as a mixture of diastereomers:
1
H NMR (300 MHz, CDCl ) δ 6.95 (d, J = 9.3 Hz, 1H), 6.67 (d, J = 7.6 Hz, 1H), 6.48 (d, J = 3.2
3
Hz, 1H), 5.70–6.40 (br. m., 3H), 4.70–4.84 (m, 1H), 4.43–4.58 (m, 2H), 3.98 (br. s., 1H), 3.63–
3
.85 (m, 3H), 3.25–3.60 (m, 3H), 3.13–3.23 (m, 1H), 2.82–3.05 (m, 2H), 2.10–2.60 (m, 2H),
1.78–1.98 (m, 1H), 1.65–1.69 (m, 1H), 1.50 (s, 9H), 1.30–1.45 (m, 1H), 1.02–1.29 (m, 2H),
13
0
.74–0.96 (m, 6H); C NMR (75 MHz, CDCl ) δ 173.4, 155.6, 135.1, 134.0, 130.0, 129.1,
3
1
24.0, 114.5, 113.1, 81.6, 62.4, 56.0, 52.2, 47.1, 34.2, 33.8, 30.7, 29.9, 28.4 (3Cs), 25.7, 23.2,
+
18.7, 16.4; MS (ESI) m/z 460.5 (M + H) . Bocꢀ14 (1.1 g, 2.4 mmol) was treated according to the
General Method 2a for removal of the Bocꢀprotection to provide 853 mg, (99% yield) of the
1
freebase compound 14 as a mixture of diastereomers: H NMR (300 MHz, CD OD) δ 6.95 (d, J
3
=
8.3 Hz, 1H), 6.63 (dd, J = 8.2, 2.6 Hz, 1H), 6.50 (d, J = 2.4 Hz, 1H), 4.01–4.10 (m, 1H), 3.93–
.95 (dd, J = 5.6, 5.2 Hz, 1H), 3.53–3.64 (m, 2H), 3.35 (s, 1H), 3.31–3.39 (m, 2H), 3.10–3.17
m, 2H), 3.00–3.07 (m, 1H), 2.80–2.99 (m, 4H), 2.38–2.56 (m, 1H), 1.80–1.87 (m, 1H), 1.55–
3
(
1
3
1
.72 (m, 2H), 1.39–1.47 (m, 1H), 0.85–0.96 (m, 9H); C NMR (75 MHz, CD OD) δ 175.4156.7,
3
137.2, 131.0, 125.6, 115.1, 113.3, 67.0, 63.5, 61.9, 61.2, 58.3, 52.2, 50.0, 43.1, 32.6, 32.2, 31.8,
+
2
0.0, 18.5, 18.1; MS (ESI) m/z 360.3 (M + H) . A white solid was obtained as the
23
dihydrochloride salt of 14: mp 164–166 °C; [α]D = +76.2° (c 1.1, CH OH). Anal.
3
(C H Cl N O •1.25 H O) C, H, N.
2
1
35
2
3
2
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Journal of Medicinal Chemistry
Page 28 of 84
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(
3R)ꢀNꢀ[(1S)ꢀ1ꢀ{[(3RS,4RS)ꢀ3,4ꢀDimethylpiperidinꢀ1ꢀyl]methyl}ꢀ2ꢀmethylpropyl]ꢀ7ꢀ
hydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxamide (15) Dihydrochloride. Compound
60d (864 mg, 4.40 mmol) in CH Cl (30 mL) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.36
2
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0
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9
0
g, 4.62 mmol) following the protocol described in General Method 1 to provide Bocꢀ15 (1.38 g,
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6
1
1
0
6%) as a mixture of diastereomers: H NMR (300 MHz, CDCl ) δ 6.98 (d, J = 8.29 Hz, 1H),
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.67 (d, J = 8.29 Hz, 1H), 6.59 (br. s., 1H), 5.76–6.35 (m, 1H), 4.64–4.93 (m, 1H), 4.48–4.63 (m,
H), 4.33–4.48 (m, 1H), 3.80 (br. s., 1H), 3.08–3.32 (m, 2H), 2.81–3.08 (m, 1H), 2.44–2.70 (m,
H), 1.80–2.39 (m, 6H), 1.69 (d, J = 11.30 Hz, 1H), 1.45–1.58 (m, 11H), 1.29–1.42 (m, 1H),
1
3
.71–1.04 (m, 12H); C NMR (75 MHz, CDCl ) δ 171.6, 155.6, 134.0, 129.1, 124.1, 114.7,
3
113.0, 81.4, 62.4, 59.0, 58.2, 56.5, 54.9, 53.6, 51.6, 44.7, 37.3, 34.3, 33.7, 32.0, 30.6, 29.8, 28.4
+
(
3 C’s), 19.2, 17.1; MS (ESI) m/z 474.7 (M + H) . Bocꢀ15 (1.38 g, 2.92 mmol) in CH CN (20
3
mL) was subjected to Boc cleavage following the General Method 2a to provide 15 (1.05 g,
1
96%) as a mixture of diastereomers: H NMR (300 MHz, CD OD) δ 6.93 (d, J = 8.29 Hz, 1H),
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6
2
2
1
1
1
.61 (dd, J = 2.54, 8.19 Hz, 1H), 6.44–6.54 (m, 1H), 3.85–4.06 (m, 2H), 3.44–3.64 (m, 1H),
.67–3.01 (m, 3H), 2.09–2.63 (m, 4H), 1.74–1.98 (m, 2H), 1.39–1.72 (m, 3H), 1.05–1.37 (m,
1
3
H), 0.81–1.02 (m, 12H); C NMR (75 MHz, CD OD) δ 175.3, 156.8, 137.4, 130.9, 125.6,
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15.0, 113.2, 63.7, 61.5, 58.2, 56.1, 54.8, 54.1, 53.2, 52.5, 38.7, 35.4, 35.1, 33.6, 32.3, 20.0,
+
7.9; MS (ESI) m/z 374.3 (M + H) . A beige solid was obtained as the dihydrochloride salt of
2
3
5: mp 158–162 °C; [α]D = +69.4° (c 1.1, CH OH). Anal. (C H Cl N O •0.75 H O) C, H, N.
3
22 37
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3
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(3R)ꢀNꢀ[(1S)ꢀ1ꢀ{[(3RS,4SR)ꢀ3,4ꢀDimethylpiperidinꢀ1ꢀyl]methyl}ꢀ2ꢀmethylpropyl]ꢀ7ꢀ
hydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxamide (16) Dihydrochloride. Compound
0e (184 mg, 0.927 mmol) in CH Cl (30 mL) was coupled with Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (327
6
2
2
mg, 1.11 mmol) following the protocol described in General Method 1 to provide Bocꢀ16 (276
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Journal of Medicinal Chemistry
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mg, 63%) as a mixture of diastereomers: H NMR (300 MHz, CDCl ) δ 6.99 (d, J = 8.48 Hz,
3
1
H), 6.53–6.81 (m, 2H), 4.69 (br. s., 1H), 4.49–4.63 (m, 1H), 4.28–4.49 (m, 1H), 3.75–3.91 (m,
0H), 3.50–3.61 (m, 1H), 3.20 (dd, J = 3.01, 14.88 Hz, 1H), 2.98 (d, J = 14.32 Hz, 1H), 2.07–2.30
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(
m, 1H), 1.50 (br. s., 9H), 1.40 (d, J = 7.16 Hz, 1H), 1.02–1.29 (m, 6H), 0.75–0.97 (m, 7H), 0.64
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(
br. s., 2H); C NMR (75 MHz, CDCl ) δ 171.5, 155.6, 134.6, 129.2, 128.9, 124.2, 114.6, 113.0,
3
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1.4, 65.8, 58.3, 56.9, 54.9, 53.5, 50.9, 45.0, 37.5, 37.3, 34.3, 34.4, 30.1, 28.7, 28.4, 19.2, 17.0;
+
MS (ESI) m/z 474.7 (M + H) . Bocꢀ16 (276 mg, 0.584 mmol) in CH OH (20 mL) was subjected
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to Boc cleavage following the General Method 2b to provide 16 (218 mg, 91%) as a mixture of
1
diastereomers: H NMR (300 MHz, CD OD) δ 6.93 (d, J = 8.29 Hz, 1H), 6.61 (dd, J = 2.54, 8.19
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Hz, 1H), 6.44–6.54 (m, 1H), 3.85–4.06 (m, 2H), 3.44–3.64 (m, 1H), 2.67–3.01 (m, 3H), 2.09–
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.63 (m, 4H), 1.74–1.98 (m, 2H), 1.39–1.72 (m, 3H), 1.05–1.37 (m, 2H), 0.81–1.02 (m, 12H);
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C NMR (75 MHz, CD OD) δ 175.3, 156.8, 137.4, 130.9, 125.6, 115.0, 113.2, 63.7, 61.5, 58.2,
3
56.1, 54.8, 54.1, 53.2, 52.5, 38.7, 35.4, 35.1, 33.6, 32.3, 20.0, 17.9; MS (ESI) m/z 374.3 (M +
+
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D
H) . A beige solid was obtained as the dihydrochloride salt of 16: mp 178–183 °C; [α]
=
+
82.1° (c 0.2, CH OH). Anal. (C H Cl N O •1.5 H O) C, H, N.
3 22 37 2 3 2 2
(
3R)ꢀNꢀ{(1S)ꢀ1ꢀ[(3,5ꢀDimethylpiperidinꢀ1ꢀyl)methyl]ꢀ2ꢀmethylpropyl}ꢀ7ꢀhydroxyꢀ1,2,3,4
tetrahydroisoquinolineꢀ3ꢀcarboxamide (17) Dihydrochloride (mixture of isomers). The
diamine 60f (766 mg, 3.57 mmol) and Bocꢀ7ꢀhydroxyꢀDꢀTicꢀOH (1.26 g, 4.29 mmol) were
treated according to the General Method 1 to provide Bocꢀ17 (1.6 g, 93%) as a mixture of
1
isomers: H NMR (300 MHz, CDCl ) δ 6.97 (d, J = 9.3 Hz, 1H), 6.67 (d, J = 7.6 Hz, 1H), 6.63
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(
d, J = 3.2 Hz, 1H), 5.94 (br. s., 1H), 4.70–4.84 (m, 1H), 4.41– 4.58 (m, 2H), 3.79 (br. s., 1H),
3
.30 (s, 3H), 3.10–3.22 (m, 2H), 2.95–3.02 (m, 1H), 2.42–2.60 (m, 2H), 1.75–2.28 (m, 6H), 1.50
1
3
(s, 9H), 1.21–1.30 (m, 2H), 0.78–0.90 (m, 6H); C NMR (75 MHz, CDCl ) δ 171.6, 155.7,
3
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