Potent and Selective Tetrahydroisoquinoline Kappa Opioid Receptor Antagonists of Lead Compound (3 R)- N-[1 R)-1-(Cyclohexylmethyl)-2-methylpropyl]-7-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamide (CDTic)

Article abstract of DOI:10.1021/acs.jmedchem.8b00674

Animal pharmacological studies suggest that potent and selective κ opioid receptor antagonists have potential as pharmacotherapies targeting depression, anxiety, and substance abuse (opiates, alcohol, nicotine, cocaine). We recently reported lead compound 1 as a new class of κ opioid receptor antagonists with only one basic amine group. Analogues were synthesized and evaluated for their in vitro opioid receptor antagonist properties using a [³⁵S]GTPγS binding assay. All analogues were pure opioid receptor antagonists with no agonist activity. Compounds 1, 8, 9, 13, and 14 (K_e values 0.058-0.64 nM) are highly potent and highly selective for the κ relative to the μ and δ opioid receptors. Favorable calculated physiochemical properties were confirmed in rat PK studies, demonstrating brain penetration for selected compounds 1, 9, and 13. High κ opioid receptor potency and selectivity and highly favorable calculated physiochemical and PK properties for brain penetration suggest these compounds should be considered for further development.

Full text of DOI:10.1021/acs.jmedchem.8b00674

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Article
Potent and Selective Tetrahydroisoquinoline Kappa
Opioid Receptor Antagonists of Lead Compound (3R)-
N-[(1R)-1-(Cyclohexylmethyl)-2-methylpropyl]-7-
hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamide (CDTic)
Chad M. Kormos, Pauline W. Ondachi, 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.8b00674 • Publication Date (Web): 22 Jul 2018
Downloaded from http://pubs.acs.org on July 23, 2018
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Potent and Selective Tetrahydroisoquinoline Kappa
Opioid Receptor Antagonists of Lead Compound
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(3R)ꢀNꢀ[1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀ
methylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (CDTic)
Chad M. Kormos, Pauline W. Ondachi, 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: Animal pharmacological studies suggest that potent and selective κ opioid
receptor antagonists have potential as pharmacotherapies targeting depression, anxiety, and
substance abuse (opiates, alcohol, nicotine, cocaine). We recently reported lead compound 1 as a
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new class of κ opioid receptor antagonists with only one basic amine group. Analogues were
synthesized and evaluated for their in vitro opioid receptor antagonist properties using a
35
[ S]GTPγS binding assay. All analogues were pure opioid receptor antagonists with no agonist
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activity. Compounds 1, 8, 9, 13, and 14 (K values 0.058–0.64 nM) are highly potent and highly
e
selective for the κ relative to the ꢁ and δ opioid receptors. Favorable calculated physiochemical
properties were confirmed in rat PK studies, demonstrating brain penetration for selected
compounds 1, 9, and 13. High κ opioid receptor potency and selectivity, and highly favorable
calculated physiochemical and PK properties for brain penetration, suggest these compounds
should be considered for further development.
INTRODUCTION
The opioid receptors belong to the superfamily of Gꢀprotein coupled receptors (GPCRs) and
1
ꢀ4
consist of the ꢁ, δ, κ subtype with the κ opioid receptor being the most abundant of the three
5
subtypes in the human brain. Since activation of the κ opioid receptor by the endogenous
dynorphin results in mood modulation, learning and memory behavioral responses to drugs of
abuse, κ opioid receptor antagonists are of high interest as potential pharmacotherapies as
6
treatments for substance abuse as well as depression and anxiety disorders. Studies from our
laboratory led to the development of the potent and selective κ opioid receptor antagonist JDTic
7
ꢀ15
16
(Figure 1) that was evaluated in a Phase I clinical study.
In addition to JDTic, LY2456302
1
7,18
and PF4455242
were developed as κ opioid receptor antagonists which reached clinical
evaluation (Figure 1). To our knowledge LY2456302, now referred to as CERCꢀ501, is the only
one of the three compounds still in clinical evaluation. CYM51317 (no structure provided) has
1
9
been reported as a new κ opioid antagonist for migraine prevention.
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In a recent communication, we reported that the structurally simple tetrahydroisoquinoline 1
(
CDTic) was a pure opioid receptor antagonist lead structure for the design and development of a
2
0
new structural class of potent and selective κ opioid receptor antagonists. In the current study,
we report the design, synthesis, and in vitro opioid receptor binding properties using the
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[
S]GTPγS binding assay of analogues of 1 represented by the general structure 2 where the R ,
2
3
4
5
R , R , R , and R groups were varied to afford the target compounds 3–20 (see Tables 1–5 for
structures). In addition, physiochemical properties were calculated to determine if the
compounds would be predicted to enter the brain and pharmacokinetic studies were conducted
on the most potent and selective κ opioid receptor antagonists which showed that the compounds
did enter the brain.
RESULTS AND DISCUSSION
Chemistry. The synthetic methods (Schemes 1–5) used to prepare the analogues of 1
20
presented in this study were analogous to the synthetic methods reported for the synthesis of 1.
As shown in Scheme 1, target compounds 3, 10, and 11 could be prepared from the same amine
2
0
2
1
which had previously been used in the synthesis of 1. Amide coupling of 21 using
dicyclohexylcarbodiimide (DCC) and hydroxybenzotriazole (HOBt) with commercially
available Bocꢀ7ꢀhydroxyꢀ(S)ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxylic acid was followed by
acid deprotection using hydrogen chloride in methanol to afford 3, a diastereomer of 1. Coupling
of amine 21 and commercially available Bocꢀ(R)ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxylic
acid using conditions similar to those used for the synthesis and deprotection of 3 afforded 10.
To prepare the target compound 11, amine 21 was coupled with Bocꢀ7ꢀfluoroꢀ(R)ꢀ1,2,3,4ꢀ
2
1
tetrahydroisoquinolineꢀ3ꢀcarboxylic acid, prepared as previously reported, using DCC and
HOBt followed by deprotection with hydrogen chloride in methanol.
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Target compounds 9, 12, and 19 (also Scheme 1) were prepared using the previously prepared
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0
Bocꢀprotected intermediate 22. Compound 9 was prepared using a sequence and conditions
2
1
similar to those previously used to synthesize JDTic analogues. First, the phenol in 22 was
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converted to an aryl triflate using Nꢀphenylꢀbis(trifluoromethanesulfonimide) (PhNTf ) followed
2
by
palladiumꢀcatalyzed
cyanation
to
give
the
intermediate
NꢀBocꢀ7ꢀcyanoꢀ
tetrahydroisoquinoline which on basic hydrolysis provided the NꢀBocꢀ7ꢀcarbamoylꢀ
tetrahydroisoquinoline intermediate. Finally, acid deprotection using hydrogen chloride in
methanol provided 9. OꢀMethylation of the phenol in 22 using methyl iodide and potassium
carbonate in acetone was followed by acid deprotection using hydrogen chloride in methanol to
afford 12. Reductive amination of formaldehyde with 1 (obtained by treating 22 with hydrogen
chloride in methanol) using sodium triacetoxyborohydride afforded the Nꢀmethyl final product
1
9.
In order to prepare the analogues 4 and 5, which are diastereomers of 1, the chiral amine 26
was prepared as shown in Scheme 2. Cyclohexylacetaldehyde (23a) was condensed with the
chiral auxiliary (S)ꢀtertꢀbutylsulfinamide to afford the sulfinimine 24. Isopropylmagnesium
chloride was added to 24 to afford the chiral sulfinamide 25. As with the preparation of amine
2
0
2
1, this reaction proceeded with high stereoselectivity. The minor diastereomer was separable
by silica gel chromatography. The chirally pure sulfinamide 25 was then cleaved to the amine 26
with hydrogen chloride in a methanol dioxane mixture. Amide coupling of 26 with the (R)ꢀ and
(S)ꢀ isomers of Bocꢀ7ꢀhydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxylic acid using DCC and
HOBt and subsequent Boc deprotection with hydrogen chloride in methanol afforded the desired
diastereomers 4 and 5, respectively. Compounds 1, 3, 4, 5 were found to be single peaks by
HPLC analysis, whereas a coꢀinjection of a either pair of diastereomers resolved as two peaks.
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As shown in Scheme 3, the same chiral auxiliary strategy was implemented with a variety of
starting aldehydes and (R)ꢀtertꢀbutylsulfinamide in order to afford the preferred chirality for
amines 29a–29e. Cyclohexylacetaldehyde (23a) was converted to sulfinimine 27a then treated
with phenylmagnesium bromide or cyclopropylmagnesium bromide to afford sulfinamides 28a
and 28b, respectively. Cyclopentylacetaldehyde (23b) was converted to sulfinimine 27b which
was treated with isopropylmagnesium chloride or cyclopropylmagensium bromide to afford the
sulfinamides 28c and 28d, respectively. Cycloheptylacetaldehyde (23c) was carried through
sulfinimine 27c then treated with isopropylmagnesium chloride to afford sulfinamide 28e using
conditions similar to that used to synthesize 28a. The sulfinamides 28a–28e were separated from
the minor diastereomer by silica gel chromatography then treated with hydrogen chloride in
methanol and dioxane to afford the chirally pure amines 29a–29e, which were used to synthesize
1
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, 8, 13, 14, 16, 17, and 20 (see Schemes 4–6).
As shown in Scheme 4, commercially available amine 30 was coupled to 7ꢀhydroxyꢀBocꢀDꢀ
TicꢀOH using DCC and HOBt and deprotected in methanol with hydrochloric acid to afford
target compound 6. Amines 29a and 29b (Scheme 3) were coupled with 7ꢀhydroxyꢀBocꢀDꢀTicꢀ
OH using DCC and HOBt followed by treatment with hydrogen chloride in dioxane and
methanol to afford target compounds 7 and 8, respectively. As shown in Scheme 5, compound 14
was synthesized by coupling amine 29e (Scheme 3) with 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH using DCC
and HOBt in THF followed by treatment with 4 N HCl in dioxane and acetonitrile.
Scheme 6 illustrates the synthesis of the analogues 13, 16, 17, and 20 starting with 29c or 29d,
1
where R = cyclopentyl in the general structure 2. Amines 29c and 29d (Scheme 3) were coupled
to 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH using DCC and HOBt to give 31 and Bocꢀ17, respectively.
Removal of the BOC groups with hydrogen chloride in dioxane and acetonitrile or methanol
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afforded the target compounds 13 and 17, respectively. A sample of 31 was converted to the aryl
triflate 32 using Nꢀphenylꢀbis(trifluoromethanesulfonamide). As an alternative to the cyanation
chemistry which was used to synthesize 9, palladiumꢀcatalyzed aminocarbonylation under sealed
vessel microwave heating directly afforded the benzamide 33. Removal of the protecting BOC
group using hydrogen chloride in dioxane and acetonitrile afforded target compound 16. Amine
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9c (Scheme 3) was also coupled to 7ꢀmethoxyꢀ3ꢀmethylꢀBocꢀDꢀTicꢀOH. Global deprotection
with boron tribromide in dichloromethane yielded the target compound 20.
Due to the immediate availability of starting materials, the cyclobutyl analogue 15 (Scheme 7)
was prepared by inverting the Grignard and sulfinimine chemistry previously illustrated in
Scheme 3. Isobutryaldehyde (34) was condensed with (S)ꢀtertꢀbutylsulfinamide using
magnesium sulfate as a dehydrating agent and pyridinium pꢀtoluenesulfonate as an acid catalyst
to afford the sulfinimine 35. Magnesium metal was used to prepare the
cyclobutylmethylmagnesium reagent from the alkyl bromide. Addition of this Grignard reagent
to the sulfinimine 35 afforded the desired sulfinamide 36. Treatment of a methanol solution of 36
with 4 N HCl in dioxane afforded the amine 37 hydrochloride, which was coupled to 7ꢀhydroxyꢀ
BocꢀDꢀTicꢀOH using propylphosphonic anhydride (T3P) and Nꢀethyldiisopropylamine in ethyl
acetate and tetrahydrofuran. Subsequent deprotection using anhydrous hydrogen chloride in
methanol afforded the desired target compound 15.
Finally, target compound 18 was accessed according to Scheme 8. Birch reduction of the
toluene derivative 38 was followed by catalytic hydrogenation using palladium on carbon
catalyst to afford the saturated ethanol derivative 39. Swern oxidation afforded the acetaldehyde,
which was condensed to the sulfinamide 40 using the same conditions used to prepare 27a–27c
in Scheme 3. Addition of isopropylmagnesium chloride to 40 and subsequent treatment with
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hydrogen chloride in dioxane and methanol afforded the amine 41 hydrochloride. This amine
was coupled with 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH using DCC and HOBt in THF followed by
deprotection using anhydrous hydrogen chloride in methanol to afford 18.
1
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Pharmacology Studies. All the synthesized compounds were tested for their abilities to inhibit
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agonistꢀstimulated [ S]GTPγS binding in membranes prepared from CHO cells expressing the
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0
ꢁ
, δ, and κ opioid receptors. In these assays, concentration response curves of control agonists
U69,593 (κ), DAMGO (ꢁ), or DPDPE (δ)) were run in the presence and absence of a single
concentration of test compound. K values were calculated with the equation K = [L]/(ER – 1)
(
e
e
where [L] is the concentration of test compound and ER is the ratio of EC50 values in the
presence and absence of test compound. K values were considered valid when the ER was at
e
least 4. Compounds were also evaluated for agonist activity at 10 ꢁM final concentration in the
35
[
S]GTPγS binding assays.
In contrast to JDTic with four stereocenters, 1 has only two asymmetric centers and thus three
diastereomeric isomers: 3, 4, and 5 (Table 1). In order to determine if one of these isomers is a
more potent and selective κ opioid receptor antagonist, the three isomers were synthesized and
tested. The three isomers (3, 4, and 5) had K values at the κ opioid receptor of 14.2, 12.6, and
e
4
.40 nM, respectively, and thus were 101ꢀ, 90ꢀ and 31ꢀfold less potent κ opioid antagonists than
1
. Compounds 3, 4, and 5 had ꢁ/κ values of 80, 41, and >682, respectively, and thus were
selective for the κ opioid receptor relative to the ꢁ opioid receptor. All three isomers have Ke
values of >3000 nM at the δ opioid receptor, making them highly selective for the κ relative to
the δ opioid receptor. However, none of the three diastereomers have better κ opioid receptor
potency and selectivity than 1. Given the stereochemical similarity of 1 and JDTic, they may
interact with the κ opioid receptor in the same fashion. This is supported by initial docking
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studies of 1 to the xꢀray structure, which predicted the two compounds to interact similarly with
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the κ opioid receptor.
The data in Table 2 gives information on the importance of the isopropyl group to the κ opioid
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receptor potency of 1. Replacement of the isopropyl group in 1 with a hydrogen to give 6
changes its K value at the κ opioid receptor from 0.14 nM for 1 to 23.5 nM for 6, a 168ꢀfold loss
e
in κ antagonist potency (Table 2). Changing the isopropyl in 1 to a phenyl ring gives 7, which
has a K = 15.2 nM at the κ opioid receptor and thus is a 109ꢀfold less potent κ opioid receptor
e
antagonist than 1. Compound 8, with a cyclopropyl group replacing the similarlyꢀsized isopropyl
group in 1, has a K = 0.64 nM at the κ opioid receptor and thus is only 4.6ꢀtimes less potent than
e
1 as κ opioid receptor antagonist. With a ꢁ/κ = 417 and δ/κ of >4690, 8 is also a very selective κ
opioid receptor antagonist relative to the ꢁ and δ opioid receptors. These results, while limited,
strongly suggest that a substituent in the 2ꢀposition is required for potent antagonism and, like
JDTic, a 2ꢀposition isopropyl group is preferred.
The effect on κ opioid antagonist potency by replacing the 7ꢀhydroxyl group in 1 with other
substituents is given in Table 3. Replacing the 7ꢀhydroxyl group in 1 with a carboxamido group
gives 9, which has K values of 178, 1220, and 0.24 nM at the ꢁ, δ and κ opioid receptors,
e
respectively, and thus is almost as potent and selective a κ opioid receptor antagonist as 1.
Replacing the 7ꢀhydroxyl group in 1 with a hydrogen or fluorine gives 10 and 11, with K values
e
of 5.49 and 10.7 nM, respectively, making the two compounds 39ꢀ and 76ꢀfold less potent than 1
as κ opioid receptor antagonists. The methoxy compound 12 with a K = 77.4 nM at the κ opioid
e
receptor is a much less potent κ antagonist than any of the other three 7ꢀsubstituted compounds
9
–11. Even though 10 and 11 are not highly potent κ opioid receptor antagonists they remain
very selective at κ relative to the ꢁ and δ opioid receptors. These results show the hydroxyl group
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in 1 can be replaced with a carboxamido group with little loss in κ antagonist potency. However,
replacement of the hydroxyl group with a hydrogen, fluoro, or methoxy group results in a
significant loss in κ opioid receptor antagonism.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
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3
3
3
3
3
4
4
4
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4
4
4
4
4
5
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5
5
5
5
5
5
5
5
6
0
1
2
3
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5
6
7
8
9
0
1
2
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9
0
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9
0
In order to determine if the cyclohexyl group in 1 offered the optimum κ opioid receptor
potency and selectivity, the cyclopentyl 13, cycloheptyl 14, and cyclobutyl 15 analogues were
synthesized and tested (Table 4). It was extremely pleasing to find that the cyclopentanyl
analogue 13 had a K = 0.058 nM at the κ opioid receptor and was 5900ꢀ and 27,000ꢀfold
e
selective for the κ relative to the ꢁ and δ receptors, respectively. With a K = 0.20 nM at the κ
e
opioid receptor, the cycloheptyl analogue 14 was almost as potent as the lead compound 1 as a κ
opioid receptor antagonist. Compound 14 also has ꢁ/κ and δ/κ values of 292 and 3760,
respectively, and thus is very selective for the κ relative to the ꢁ and δ opioid receptors. In
contrast to 1, 13, and 14, which possess cyclohexyl, cyclopentyl, and cycloheptyl rings,
respectively, the smaller cyclobutane ring analogue 15 had a K = 2.61 nM at the κ opioid
e
receptor and was only 69ꢀfold selective for the κ relative to the ꢁ opioid receptor. However, with
a δ/κ value >1150, 15 remained highly selective for the κ relative to the δ opioid receptor. Since
the carboxamide 9 (see Table 3) and the cyclopropyl 8 analogues of 1 (see Table 2) both had
subnanomolar κ potencies and high selectivity for the κ relative to the ꢁ and δ receptors, the
carboxamide 16 and cyclopropyl 17 analogues of 13 were synthesized and tested (Table 4).
Although the carboxamide analogue 16 had a K = 2.04 nM at the κ opioid receptor and was 102ꢀ
e
and 1245ꢀfold selective for the κ relative to the ꢁ and δ opioid receptors, respectively, it was not
as potent and κ selective as the carboxamide analogue 9. Similarly, the cyclopropyl analogue 17,
with a K = 3.74 nM at the κ opioid receptor, did not retain the potency nor selectivity of the
e
analogous cyclopropyl analogue 8. The most important finding from this study is that
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replacement of the cyclohexyl group in 1 with a cyclopentyl group resulted in a significant
increase in κ opioid receptor antagonist potency. It is also interesting that replacement of the
isopropyl group in 13 with a cyclopropyl group to give 17 resulted in a large loss in κ antagonist
potency.
0
1
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It is well documented that methyl groups can have a significant effect on the potency of target
2
1,23
24
compounds.
the 4ꢀposition on the piperidine ring of compound 42 to give the 4ꢀmethyl analogue 4ꢀMePDTic
43) resulted in a 18ꢀfold increase in the κ opioid receptor potency relative to 42; therefore, we
Furthermore, in a recent study we found that the addition of a methyl group to
(
investigated the effect of adding a 4ꢀmethyl group to 1 (Table 5). Compound 18, which is the 4ꢀ
methyl analogue of 1, has a K = 1.27 nM at the κ opioid receptor and thus is 9 times less potent
e
than 1, which has a K = 0.14 nM at the κ opioid receptor. With ꢁ/κ and δ/κ values of >174 and
e
>2400, 18 remains very selective for κ relative to ꢁ and δ opioid receptors.
Two methylꢀsubstituted JDTicꢀanalogues, 44 and 45, were potent and selective κ opioid
2
2,25
receptor antagonists with shorter durations of action in a mouse antinociception test.
For
comparison, the Nꢀmethyl 19 analogue of 1 and the 3ꢀmethyl 20 analogue of 13 were synthesized
and tested (Table 5). The Nꢀmethyl analogue 19 (Table 5) had K values of 245, >3000, and 4.23
e
nM at the ꢁ, δ, and κ opioid receptors, respectively. Thus, 19 is 30ꢀfold less potent than its parent
1
at the κ opioid receptor. In the JDTic series, the Nꢀmethyl analogue 44, with a K = 0.16 nM
e
represented only an 8ꢀfold decrease in potency from its parent, JDTic. The 3ꢀmethyl analogue 20
had K values of 1650, >3000, and 6.20 nM at the ꢁ, δ, and κ opioid receptors, respectively.
e
Thus, 20 is 107ꢀfold less potent at the κ opioid receptor than its parent compound 13. In contrast,
the methylatedꢀJDTic analogue 45 had K values of 3.6, 854, and 0.03 nM at the ꢁ, δ and κ
e
opioid receptors, respectively, and was thus only 1.5ꢀtimes less potent than JDTic at the κ opioid
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receptor. These comparisons show that this new tetrahydroisoquinoline class of opioid
antagonists has a different structure–activity relationship than JDTic, 44, and 45.
Table 6 shows a comparison of the calculated physiochemical properties of six of the more
potent κ opioid receptor antagonists from this study, along with JDTic. Reports from other
laboratories predict that compounds with topological polar surface area (TPSA) values less than
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
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5
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7
8
9
0
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9
0
2
6
27
28
7
6 Å, cLogP values in the range of 2–4, logBB values greater than –1, and CNS MPO
2
9
values greater than 4 will penetrate the brain. All the compounds represented in Table 6 except
have TPSA values of 61.36 Å, which is less than 76 Å. Like JDTic, compound 9 has a TPSA
9
value of 84.22 Å which is similar to the 84.83 Å value for JDTic. The cLogP values for the six
new tetrahydroisoquinolines ranged from 3.31 for 9 to 4.48 for 14 compared to 3.60 for JDTic.
All six new tetrahydroisoquinoline analogues, as well as JDTic, have logBB values greater than
–
1 and thus would be predicted to penetrate the brain. Compounds 8, 13, and 9 have favorable
CNS MPO values of 4.2, 4.2, and 4.4, respectively. Compounds 1, 14, and 18 had CNS MPO
scores of 3.7, 3.4, and 3.5, respectively. In a recent review concerning the various methods used
for predicting the ability of a compound to cross the blood/brain barrier, Pike pointed out that
lower molecular weight compounds tended to penetrate the brain better than higher molecular
2
9,30
weight compounds.
The six new tetrahydroisoquinoline compounds in Table 6 had molecular
weights ranging from 330.4 Daltons for 13 up to 371.5 Daltons for 9. The highly potent and
selective κ opioid receptor antagonist 13, with a molecular weight of 330.4 Daltons, has a
molecular weight 135.2 Daltons less than JDTic at 465.8 Daltons.
Pharmacokinetic Studies. Rats were administered a single 5 mg/kg s.c. dose for 1, 9, or 13,
and each compound was quantitated in plasma and brain homogenate at times between 1 and 168
h. Concentration versus time data was analyzed by a noncompartmental analysis using Phoenix
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WinNonlin 6.3 (Pharsight, Cary, NC). In plasma, tmax for 1 was 1 h in plasma and brain, with
Cmax values of 111 and 524 ng/mL, respectively, indicating rapid absorption (Table 7 and Figure
2). Compound 1 was readily determined throughout the 168 h collection period in both brain and
plasma. The halfꢀlife was determined to be 34.2 h in plasma and 78.2 h in brain. The levels of 1
in brain remained elevated while the levels in plasma dropped substantially, resulting in a
substantially higher value for area under the curve (AUC) in brain, and a ratio of AUC in
brain:plasma of 8.15:1; the clearance was 11.7 times slower from the brain relative to plasma.
Compound 9 was rapidly cleared from plasma and brain with Cmax in both at 1 h, with values of
0
1
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9
0
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9
0
3
76 and 131 ng/mL, respectively (Figure 2, see Figure S1 in Supporting Information for an extra
depiction of Figure 2.). Compound 9 was not detected in plasma or brain at timepoints after 24 h,
with the halfꢀlives of 1.9 h in plasma, and 2.3 h in brain (Table 7). In plasma, 13 reached Cmax of
1
36 ng/mL at 1 h post dose; in brain, a Cmax of 575 ng/mL was also achieved at 1 h post dose.
The halfꢀlife was determined to be 32 h in plasma, and 45 h in brain. Compound 13 crossed the
bloodꢀbrain barrier and persisted in plasma and brain for 168 h post dose. The ratio of
brain:plasma AUC was 6.08:1 and the clearance was 6.1 times slower from the brain relative to
the plasma, indicating that 13 crossed the bloodꢀbrain barrier and persisted in brain. JDTic in
comparison had a half life of 28.4 and 51.8 h in plasma and brain, respectively, and a ratio of
31
brain/plasma AUClast of 6.87. Both 1 and 13 have similar pharmacokinetic behavior to JDTic,
whereas 9 is very different, with a much shorter half life in both brain and plasma, and no
differential persistence in the brain.
Conclusions
In conclusion, analogues 3–20 of the lead structure 1 were synthesized and evaluated for their
3
5
ability to antagonize [ S]GTPγS binding at the ꢁ, δ, and κ opioid receptors. The data showed
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that 13, which has a cyclopentyl in place of the cyclohexyl in 1, with a K = 0.058 nM at the κ
e
opioid receptor and 5900ꢀ and 27,000ꢀfold selectivity for the κ relative to the ꢁ and δ receptors,
respectively, was the most potent and selective κ opioid receptor analogue of 1. In addition, the
1
1
1
1
1
1
1
1
1
1
2
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0
7
ꢀcarboxamido analogue 9 and the cycloheptyl analogue 14 had subnanomolar K values at the κ
e
opioid receptor and were highly selective for the κ relative to the ꢁ and δ opioid receptors.
Calculated logBB and CNS MPO values along with low molecular weight values relative to
JDTic suggested that 1, 9, and 13 would penetrate the brain. Data from PK studies in rats showed
that 1 and 13 did indeed penetrate the brain. The cyclopentyl group (13) in place of the
cyclohexyl group (1) did not make a significant change in Cmax, tmax, or AUC in plasma, but in
brain, the change substantially decreased halfꢀlife and AUC. Substitution of the hydroxy group in
1
with the carboxamido group in 9 substantially reduced the halfꢀlives in brain and plasma, as
well as the AUC values in brain and plasma.
Experimental Procedures
Melting points were determined using a MELꢀTEMP II capillary melting point apparatus.
1
13
19
Nuclear magnetic resonance ( H NMR, C NMR and F NMR ) spectra were obtained on a
Bruker Avance DPXꢀ300 MHz NMR spectrometer or a Varian Unity Inova 500 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 the 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 chamber. Flash
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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: DMA80 =
80:18:2 CH Cl :CH OH:conc. NH OH. Unless otherwise stated, reagentꢀgrade chemicals were
2
2
3
4
0
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obtained from commercial sources and were used without further purification. All moistureꢀ and
airꢀsensitive reactions and reagent transfers were carried out under dry nitrogen. Sealed tube
reactions were run in a CEM Discover SP microwave synthesizer. 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.
(3S)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (3) Hydrochloride.
A
solution
of
dicyclohexylcarbodiimide (DCC) (120 mg, 0.58 mmol) in THF (2 mL) was added to a solution
of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀLꢀTicꢀOH (150 mg, 0.51 mmol) in THF (3
mL). After 1 h, the amine 21 (120 mg, 0.6 mmol) and NEt (0.2 mL, 1.4 mmol) were added to
3
the suspension. The reaction mixture was stirred at room temperature for 12 h. The solids were
separated by filtration, and the filtrate concentrated to a residue. The residue was subjected to
chromatography on silica gel eluting with a gradient of 0–75% EtOAc in hexanes. The product
containing fractions were concentrated and the residue dissolved in CH OH (5 mL) and treated
3
with 6 N HCl (aq) (5 mL). After 1 h, the solution was concentrated, and the resulting residue
partitioned between EtOAc and 7 M NH OH (aq). The organic layer was dried (Na SO ) and
4
2
4
concentrated. The resulting residue was subjected to chromatography on silica gel eluting with a
1
gradient EtOAc in hexanes to afford the 3 freebase: H NMR (300 MHz, CDCl ) δ 7.03 (d, J =
3
9
.98 Hz, 1H), 6.97 (d, J = 8.29 Hz, 1H), 6.66 (dd, J = 2.54, 8.19 Hz, 1H), 6.54 (d, J = 2.45 Hz,
1H), 3.85–3.97 (m, 3H), 3.58 (dd, J = 5.27, 9.98 Hz, 1H), 3.12 (dd, J = 5.18, 16.11 Hz, 1H), 2.76
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(
dd, J = 9.98, 16.01 Hz, 1H), 1.54–1.92 (m, 9H), 1.04–1.38 (m, 6H), 0.72–1.02 (m, 7H);
C
NMR (75 MHz, CDCl ) δ 172.3, 154.8, 135.7, 129.9, 125.1, 114.2, 112.2, 56.5, 51.2, 46.9, 39.8,
3
34.6, 34.2, 32.6, 32.3, 30.5, 26.5, 26.4, 26.1, 19.1, 17.5. The freebase was converted into the
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
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3
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3
3
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4
4
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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
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2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
hydrochloride salt to afford 123.3 mg (63% over two steps) of a white powder: MS (ESI) m/z
+
3
45.2 (M + H) ; mp 149–153 °C (fusion); [α]D = –43° (c 0.10, CH OH). Anal.
3
(C H ClN O ꢂ0.5 H O) C, H, N.
21 33 2 2 2
(3R)ꢀNꢀ[(1S)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (4) Hydrochloride. A solution of DCC (110 mg, 0.53
mmol) in THF (2 mL) was added to a solution of HOBt (70. mg, 0.52 mmol) and 7ꢀhydroxyꢀ
BocꢀDꢀTicꢀOH (150 mg, 0.50 mmol) in THF (3 mL). After 1 h, the amine 26 (90. mg, 0.44
mmol) and NEt (0.3 mL, 2.2 mmol) were added to the suspension. The reaction mixture was
3
stirred at room temperature for 12 h. The solids which precipitated during the course of the
reaction were separated by filtration, and the filtrate concentrated to a residue. The residue was
subjected to chromatography on silica gel eluting with 0–100% EtOAc in hexanes. The product
containing fractions were concentrated and the residue dissolved in CH OH (5 mL) and treated
3
with 6 N HCl (aq) (5 mL). After 1 h, the solution was concentrated, and the residue partitioned
between EtOAc and sat. NaHCO . The organic layer was dried (Na SO ) and concentrated. The
3
2
4
residue was subjected to chromatography on silica gel eluting with a gradient of 0–75% EtOAc
1
in hexanes to afford the 4 freebase: H NMR (300 MHz, CDCl ) δ 6.94 (d, J = 8.29 Hz, 1H),
3
6.66 (dd, J = 2.45, 8.29 Hz, 1H), 6.52 (d, J = 2.26 Hz, 1H), 3.95 (d, J = 8.48 Hz, 2H), 3.88 (td, J
=
4.59, 9.47 Hz, 1H), 3.63 (dd, J = 5.09, 10.17 Hz, 1H), 3.06 (dd, J = 5.09, 16.01 Hz, 1H), 2.71–
2
.84 (m, 1H), 1.82 (d, J = 13.19 Hz, 1H), 1.54–1.76 (m, 5H), 1.07–1.38 (m, 7H), 0.87–1.04 (m,
13
1H), 0.83 (d, J = 6.97 Hz, 6H); C NMR (75 MHz, CDCl ) δ 172.3, 155.1, 135.3, 129.8, 124.6,
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1
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2
2
2
2
2
2
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3
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1
14.3, 112.2, 56.4, 51.2, 46.7, 39.7, 34.6, 34.1, 32.6, 32.3, 30.5, 26.5, 26.3, 26.1, 19.0, 17.4. The
freebase was converted into the hydrochloride salt to afford 14.5 mg (9% over two steps) of a
+
white powder: MS (ESI) m/z 345.2 (M + H) ; mp 150–154 °C (fusion); [α] = +38° (c 0.10,
D
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
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1
2
3
4
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7
8
9
0
1
2
3
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5
6
7
8
9
0
CH OH). Anal. (C H ClN O ꢂ1.15 H O) C, H, N.
3
21 33
2
2
2
(3S)ꢀNꢀ[(1S)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (5) Hydrochloride. A solution of DCC (120 mg, 0.58
mmol) in THF (2 mL) was added to a solution of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀ
LꢀTicꢀOH (150 mg, 0.51 mmol) in THF (3 mL). After 1 h, the amine 26 hydrochloride (116 mg,
0
.57 mmol) and NEt (0.2 mL, 1.4 mmol) were added to the suspension. The reaction mixture
3
was stirred at room temperature for 12 h. The solids were separated by filtration, and the filtrate
concentrated to a residue. The residue was subjected to chromatography on silica gel eluting with
a gradient of 0–75% EtOAc in hexanes. The product containing fractions were concentrated and
the residue dissolved in CH OH (5 mL) and treated with 6 N HCl (aq) (5 mL). After 1 h, the
3
solution was concentrated and taken up in 50% DMA80. The solids were separated by filtration
and the organic layer was concentrated. The resulting residue was subjected to chromatography
1
on silica gel eluting with a 25% DMA80 in CH Cl to afford the 5 freebase: H NMR (300 MHz,
2
2
CDCl ) δ 6.83–7.02 (m, 2H), 6.61 (dd, J = 2.45, 8.10 Hz, 1H), 6.49 (d, J = 2.26 Hz, 1H), 3.76–
3
3
1
.97 (m, 3H), 3.52 (dd, J = 5.09, 10.17 Hz, 1H), 3.07 (dd, J = 5.18, 16.11 Hz, 1H), 2.67 (dd, J =
1
3
0.17, 16.01 Hz, 1H), 1.40–1.82 (m, 6H), 0.93–1.33 (m, 7H), 0.61–0.92 (m, 9H); C NMR (75
MHz, CDCl ) δ 172.7, 154.7, 136.3, 130.0, 125.4, 114.3, 112.3, 56.7, 51.2, 47.2, 39.7, 34.6,
3
3
4.2, 32.6, 32.4, 30.6, 26.5, 26.3, 26.1, 19.1, 17.7. The freebase was converted into the
hydrochloride salt to afford 68.3 mg (36% over two steps) of a white powder: MS (ESI) m/z
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+
3
45.3 (M + H) ; mp 265–269 °C (fusion); [α] = –101° (c 0.10, CH OH). Anal. (C H ClN O )
D 3 21 33 2 2
C, H, N.
(3R)ꢀNꢀ(2ꢀCyclohexylethyl)ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀcarboxamide (6)
Hydrochloride. A solution of DCC (120 mg, 0.58 mmol) in THF (2 mL) was added to a solution
of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH (150 mg, 0.51 mmol) in THF (3
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
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4
4
4
4
4
4
5
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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
mL). After 1 h, 2ꢀcyclohexylethylamine (30) hydrochloride (96 mg, 0.6 mmol) and NEt (0.25
3
mL, 1.7 mmol) were added to the suspension. The reaction mixture was stirred at room
temperature for 12 h. The solids were separated by filtration, and the filtrate concentrated to a
residue. The residue was subjected to chromatography on silica gel eluting with a gradient of 0–
50% EtOAc in hexanes. The product containing fractions were concentrated and the residue
dissolved in CH OH (5 mL) and treated with 4 N HCl in dioxane (5 mL). After 12 h, the solution
3
was concentrated, and the residue partitioned between EtOAc and sat. NaHCO (aq). The organic
3
layer was dried (Na SO ) and concentrated. The residue was subjected to chromatography on
2
4
1
silica gel eluting with a gradient of 0–100% EtOAc in hexanes to afford the 6 freebase: H NMR
300 MHz, CD OD) δ 8.38 (br. s., 1H), 7.08 (d, J = 8.48 Hz, 1H), 6.75 (dd, J = 2.45, 8.48 Hz,
(
3
1
4
H), 6.63 (s, 1H), 4.33 (s, 2H), 4.11 (dd, J = 4.80, 11.77 Hz, 1H), 3.53–3.78 (m, 1H), 3.22 (d, J =
13
.71 Hz, 1H), 2.92–3.13 (m, 1H), 1.60–1.82 (m, 6H), 1.07–1.53 (m, 7H), 0.80–1.06 (m, 2H); C
NMR (75 MHz, CD OD) δ 169.5, 169.4, 158.1, 131.1, 129.7, 122.1, 116.9, 113.7, 56.9, 45.6,
3
3
8.5, 38.4, 37.8, 36.5, 34.3, 34.2, 30.4, 27.6, 27.3. The freebase was converted into the
+
hydrochloride salt to afford 50 mg (28%) of an offꢀwhite powder: MS (ESI) m/z 303.1 (M + H) ;
mp 78–82 °C (fusion); [α] = +99° (c 0.32, CH OH). Anal. (C H ClN O ꢂ0.75 H O) C, H, N.
D
3
18 27
2
2
2
(
3R)ꢀNꢀ[(1R)ꢀ2ꢀCyclohexylꢀ1ꢀphenylethyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀ
carboxamide (7) Hydrochloride. A solution of DCC (120 mg, 0.58 mmol) in THF (2 mL) was
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6
added to a solution of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH (150 mg, 0.51
mmol) in THF (3 mL). After 1 h, the amine 29a (144 mg, 0.60 mmol) and NEt (0.2 mL, 1.4
3
mmol) were added to the suspension. The reaction mixture was stirred at room temperature for
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
1
2 h. The solids were removed by filtration, and the filtrate concentrated to a residue. The
residue was subjected to chromatography on silica gel eluting with a gradient of 0–50% EtOAc
in hexanes. The product containing fractions were concentrated and the residue dissolved in
CH OH (5 mL) and treated with 4 N HCl in dioxane (5 mL). After 12 h, the solution was
3
concentrated, and the residue partitioned between EtOAc and sat. NaHCO (aq). The organic
3
layer was dried (Na SO ) and concentrated. The residue was subjected to chromatography on
2
4
1
silica gel eluting with a gradient of 0–100% EtOAc in hexanes to afford the 7 freebase: H NMR
(
300 MHz, CD OD) δ 7.14–7.38 (m, 5H), 6.88 (d, J = 8.10 Hz, 1H), 6.57 (dd, J = 2.54, 8.19 Hz,
3
1
H), 6.48 (d, J = 2.26 Hz, 1H), 5.00 (dd, J = 6.03, 9.42 Hz, 1H), 3.91 (s, 2H), 3.53 (dd, J = 4.71,
10.17 Hz, 1H), 2.74–2.90 (m, 1H), 2.58–2.74 (m, 1H), 1.47–1.87 (m, 8H), 1.07–1.36 (m, 5H),
13
0
.80–1.06 (m, 3H); C NMR (75 MHz, CD OD) d 174.7, 156.8, 144.8, 137.1, 130.8, 129.6,
3
1
28.1, 127.5, 125.5, 114.9, 113.1, 58.0, 52.0, 47.8, 45.5, 35.6, 34.7, 33.9, 32.1, 27.6, 27.3, 27.2.
The freebase was converted into the hydrochloride salt to afford 25.3 mg (12%) of an offꢀwhite
+
powder: MS (ESI) m/z 379.5 (M + H) ; mp 139–143 °C (fusion); [α] = +67° (c 0.10, CH OH).
D
3
Anal. (C H ClN O ꢂ0.75 H O) C, H, N.
2
4
31
2
2
2
(3R)ꢀNꢀ[(1R)ꢀ2ꢀCyclohexylꢀ1ꢀcyclopropylethyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ
3ꢀcarboxamide (8) Hydrochloride. A solution of DCC (120 mg, 0.58 mmol) in THF (2 mL)
was added to a solution of HOBt (72 mg, 0.54 mmol) and 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH (150 mg,
0
.51 mmol) in THF (3 mL). After 1 h, the amine 29b (120 mg, 0.59 mmol) and NEt (0.2 mL,
3
1.4 mmol) were added to the suspension. The reaction mixture was stirred at room temperature
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for 12 h. The solids were removed by filtration, and the filtrate concentrated to a residue. The
residue was subjected to chromatography on silica gel eluting with a gradient of 0–50% EtOAc
in hexanes. The product containing fractions were concentrated and the residue dissolved in
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
CH OH (5 mL) and treated with 6 N HCl (aq) (5 mL). After 12 h, the solution was concentrated,
3
and the residue partitioned between EtOAc and sat. NaHCO (aq). The organic layer was dried
3
(
Na SO ) and concentrated. The residue was subjected to chromatography on silica gel eluting
2 4
1
with a gradient of 0–100% EtOAc in hexanes to afford 51.8 mg (30%) of the 8 freebase: H
NMR (300 MHz, CD OD) δ 6.91 (d, J = 8.29 Hz, 1H), 6.60 (dd, J = 2.45, 8.29 Hz, 1H), 6.49 (d,
3
J = 2.26 Hz, 1H), 3.83–4.00 (m, 2H), 3.37–3.55 (m, 2H), 2.67–2.99 (m, 2H), 1.79 (d, J = 12.43
Hz, 1H), 1.55–1.73 (m, 4H), 1.40–1.50 (m, 2H), 1.05–1.39 (m, 6H), 0.72–1.04 (m, 4H), 0.25–
13
0
.57 (m, 3H), 0.11–0.25 (m, 1H); C NMR (75 MHz, CD OD) δ 174.8, 156.8, 137.1, 130.9,
3
1
25.6, 115.0, 113.2, 58.0, 51.8, 47.8, 44.2, 35.4, 35.2, 33.9, 32.4, 27.7, 27.4, 27.3, 17.9, 4.2, 2.9.
The freebase was converted into the hydrochloride salt to afford an offꢀwhite powder: MS (ESI)
+
m/z 343.4 (M + H) ; mp >250 °C; [α] = +88° (c 0.10, CH OH). Anal. (C H ClN O ) C, H, N.
D
3
21 31
2
2
3
(
3R)ꢀN ꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3,7ꢀ
dicarboxamide (9) Hydrochloride. A sample of the white foam 22 (3.16 g, 7.1 mmol) was
dissolved in CH Cl (50 mL) and treated with PhNTf (3.6 g, 10 mmol) and NEt (22 mmol, 3
2
2
2
3
mL). After 12 h, the reaction mixture was washed with sat. NH Cl (aq) then NaHCO and dried
4
3
over Na SO . The organic layer was concentrated to a residue which was subjected to
2
4
chromatography on silica gel eluting with a gradient of 0–50% EtOAc in hexanes to afford 3.57
1
g (87%) of the desired aryl triflate: H NMR (300 MHz, CDCl ) δ 7.32 (d, J = 8.29 Hz, 1H), 7.15
3
(d, J = 8.10 Hz, 1H), 7.10 (br. s., 1H), 5.30–6.03 (m, 1H), 4.74–5.13 (m, 1H), 4.63 (br. s., 2H),
3.77 (br. s., 1H), 3.34–3.52 (m, 1H), 2.88–3.15 (m, 1H), 1.31–1.73 (m, 16H), 0.89–1.23 (m, 5H),
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2
2
2
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5
5
5
5
5
5
5
6
19
0
.83 (dd, J = 6.78, 12.62 Hz, 6H), 0.42–0.74 (m, 2H); F NMR (282 MHz, CDCl ) δ –126.3. A
3
solution of the aryl triflate (1.0 g, 1.7 mmol) with Zn(CN) (347 mg, 3.0 mmol) in DMF (2.1
2
mL) was deꢀgassed before Pd(PPh ) (70 mg, 3.5 mol%) was added. The reaction mixture was
3
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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9
0
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8
9
0
1
2
3
4
5
6
7
8
9
0
heated in a sealed microwave tube for 4 h at 100 °C. The reaction mixture was diluted with ether,
washed with water, then sat. NaHCO (aq), then LiCl (aq), then brine. The resulting organic
3
layer was dried (Na SO ) then concentrated. The resulting residue was subjected to
2
4
chromatography on silica gel elution with a gradient of 0–50% EtOAc in hexanes to afford 0.60
+
g (75%) of the desired benzonitrile: MS (ESI) m/z 454.3 (M + H) . The benzonitrile (0.60 g, 1.3
mmol) was dissolved in dioxane (8 mL) and treated with LiOHꢂH O (133 mg, 3.2 mmol) in
2
water (4 mL). Finally, 30% H O (1 mL) was added and the reaction mixture was stirred for 48
2
2
h. The reaction mixture was diluted with ether, washed with sat. NH Cl (aq), dried (Na SO ) and
4
2
4
then concentrated. The resulting residue was subjected to chromatography on silica gel eluting
with a gradient of 0–50% EtOAc in hexanes to afford the Boc protected compound. This
intermediate was dissolved in CH OH (5 mL) and added to a cold solution of methanoic HCl
3
prepared earlier from CH OH (5 mL) and acetyl chloride (1 mL). After 12 h under a stream of
3
nitrogen, the solids were reꢀdissolved in a minimum of methanol and diluted with EtOAc. A
small addition of hexanes initiated crystallization. The solids were collected and dried to afford
5
10 mg (89% over two steps) of the desired hydrochloride salt as a white crystalline solid. A
1
sample of the 9 hydrochloride salt was converted to the 9 freebase for NMR characterization: H
NMR (300 MHz, CD OD) δ 7.65 (d, J = 8.10 Hz, 1H), 7.59 (s, 1H), 7.19 (d, J = 7.91 Hz, 1H),
3
3
.95–4.15 (m, 2H), 3.86 (d, J = 5.65 Hz, 1H), 3.54–3.70 (m, 1H), 3.33–3.39 (m, 1H), 2.82–3.16
(
m, 2H), 1.98–2.08 (m, 2H), 1.85 (d, J = 12.06 Hz, 1H), 1.53–1.77 (m, 5H), 1.05–1.40 (m, 7H),
1
3
0.69–1.04 (m, 8H); C NMR (75 MHz, CD OD) δ 173.6, 170.9, 138.4, 135.7, 131.7, 129.0,
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25.6, 125.3, 56.1, 51.5, 46.4, 39.5, 34.5, 34.3, 32.8, 32.5, 32.0, 26.6, 26.4, 26.1, 18.7, 17.3. The
+
compound was further characterized as the hydrochloride salt: MS (ESI) m/z 372.3 (M + H) ; mp
132–136 °C (fusion); [α] = +96° (c 0.10, CH OH). Anal. (C H ClN O ꢂ1.75 H O) C, H, N.
D
3
22 35
3
2
2
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
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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
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1
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7
8
9
0
1
2
3
4
5
6
7
8
9
0
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3ꢀ
carboxamide (10) Hydrochloride. Dicyclohexylcarbodiimide (47.5 mg, 0.23 mmol) was added
to a solution of HOBt (29 mg, 0.22 mmol) and BocꢀDꢀTicꢀOH (55.4 mg, 0.20 mmol) in THF (2
mL). After 1 h, the amine 21 hydrochloride (49.4 mg, 0.24 mmol) and NEt (0.08 mL, 0.6 mmol)
3
were added to the suspension. The reaction mixture was stirred at room temperature for 12 h.
The solids were separated by filtration, and the filtrate concentrated to a residue. The residue was
subjected to chromatography on silica gel eluting with a gradient of 0–75% EtOAc in hexanes.
The product containing fractions were concentrated and the residue dissolved in CH OH (5 mL)
3
and treated with 6 N HCl (aq) (5 mL). After 1 h, the solution was concentrated, and the residue
partitioned between CH Cl and sat. Na CO (aq). The organic layer was dried (Na SO ) and
2
2
2
3
2
4
concentrated. The residue was subjected to chromatography on silica gel eluting with a gradient
1
EtOAc in hexanes to afford the 10 freebase: H NMR (300 MHz, CDCl ) δ 7.12–7.23 (m, 3H),
3
7
1
1
1
.03–7.12 (m, 1H), 6.97 (d, J = 9.80 Hz, 1H), 4.04 (s, 2H), 3.85–3.99 (m, 1H), 3.74–3.82 (m,
H), 3.56–3.70 (m, 2H), 3.25 (dd, J = 5.09, 16.39 Hz, 1H), 2.85 (dd, J = 10.17, 16.39 Hz, 1H),
13
.51–1.89 (m, 6H), 1.05–1.40 (m, 6H), 0.71–1.01 (m, 7H); C NMR (75 MHz, CDCl ) δ 172.5,
3
35.8, 134.4, 129.1, 126.7, 126.2, 125.6, 56.5, 50.9, 47.4, 39.8, 34.6, 34.2, 32.6, 32.4, 31.4, 26.5,
26.4, 26.1, 19.1, 17.7. The freebase was converted into the hydrochloride salt to afford 48.5 mg
+
(
66% over two steps) of a white powder: MS (ESI) m/z 329.3 (M + H) ; mp 210–214 °C
fusion); [α] = +104° (c 0.10, CH OH). Anal. (C H ClN O) C, H, N.
(
D
3
21 33
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(
3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀfluoroꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (11) Hydrochloride. Dicyclohexylcarbodiimide (63
mg, 0.31 mmol) was added to a solution of HOBt (44 mg, 0.33 mmol) and 7ꢀfluoroꢀBocꢀDꢀTicꢀ
OH (81 mg, 0.27 mmol) in THF (2.5 mL). After 1 h, the amine 21 (62 mg, 0.30 mmol) and NEt3
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
(
0.2 mL, 1.4 mmol) in THF (0.5 mL) were added to the suspension. The reaction mixture was
stirred at room temperature for 12 h. The solids were separated by filtration, and the filtrate
concentrated to a residue. The residue was subjected to chromatography on silica gel eluting with
a gradient of 0–50% EtOAc in hexanes. The product containing fractions were concentrated and
the residue dissolved in CH OH (5 mL) and treated with 6 N HCl (aq) (5 mL). After 12 h, the
3
solution was concentrated, and the residue partitioned between EtOAc and sat. Na CO (aq). The
2
3
organic layer was dried (Na SO ) and concentrated. The residue was subjected to
2
4
chromatography on silica gel eluting with a gradient of 0–75% EtOAc in hexanes to afford the
1
11 freebase: H NMR (300 MHz, CDCl ) δ 7.13 (dd, J = 5.65, 8.29 Hz, 1H), 6.83–7.00 (m, 2H),
3
6
.78 (dd, J = 2.45, 9.04 Hz, 1H), 4.01 (d, J = 5.09 Hz, 2H), 3.93 (dt, J = 4.90, 9.80 Hz, 1H), 3.59
(
dd, J = 5.27, 9.80 Hz, 1H), 3.20 (dd, J = 5.18, 16.29 Hz, 1H), 2.81 (dd, J = 9.80, 16.20 Hz, 1H),
1
3
1
.95 (br. s., 1H), 1.51–1.87 (m, 6H), 1.02–1.40 (m, 6H), 0.70–1.01 (m, 8H); C NMR (75 MHz,
CDCl ) δ 172.2, 161.2 (d, J = 243 Hz), 137.4 (d, J = 7.3 Hz), 130.5 (d, J = 7.3 Hz), 129.9 (d, J =
3
3
.6 Hz), 113.7 (d, J = 21 Hz), 112.1 (d, J = 21 Hz), 56.4, 50.9, 47.3, 39.8, 34.6, 34.2, 32.6, 32.4,
3
0.6, 26.5, 26.3, 26.1, 19.1, 17.7. The freebase was converted into the hydrochloride salt to
+
afford 58.1 mg (56% over two steps) of a white powder: MS (ESI) m/z 347.5 (M + H) ; mp 232–
2
36 °C (fusion); [α] = +107° (c 0.10, CH OH). Anal. (C H ClFN Oꢂ0.25 H O) C, H, N.
D 3 21 32 2 2
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀmethoxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (12) Hydrochloride. A solution of 22 (127 mg, 0.29
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mmol) in acetone (5 mL) was treated with K CO (140 mg, 1 mmol) and iodomethane (460 mg,
2
3
3
.2 mmol). After stirring 12 h at ambient temperature, the suspension was filtered. The filtrate
was concentrated, and the resulting residue dissolved in CH OH (5 mL) and treated with 6 M
3
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
HCl (aq) (5 mL). After 2 h, the solution was concentrated, and the resulting residue was
dissolved in EtOAc and washed with sat. Na CO (aq). The organic layer was concentrated and
2
3
the residue subjected to chromatography on silica gel eluting with a gradient of EtOAc in
1
hexanes to afford the 12 freebase: H NMR (300 MHz, CDCl ) δ 7.10 (d, J = 8.48 Hz, 1H), 6.95
3
(d, J = 9.98 Hz, 1H), 6.76 (dd, J = 2.64, 8.29 Hz, 1H), 6.62 (d, J = 2.64 Hz, 1H), 3.86–4.05 (m,
3
H), 3.79 (s, 3H), 3.53–3.66 (m, 1H), 3.19 (dd, J = 5.18, 16.11 Hz, 1H), 2.78 (dd, J = 10.17,
13
16.20 Hz, 1H), 1.51–1.88 (m, 6H), 1.05–1.40 (m, 7H), 0.71–1.00 (m, 8H); C NMR (75 MHz,
CDCl ) δ 172.4, 158.0, 136.6, 130.0, 126.4, 112.6, 110.7, 56.8, 55.3, 50.9, 47.6, 39.8, 34.6, 34.2,
3
3
2.6, 32.4, 30.6, 26.5, 26.3, 26.1, 19.1, 17.7. The freebase was converted into the hydrochloride
+
salt to afford 29.4 mg (25% over two steps) of a white powder: MS (ESI) m/z 359.5 (M + H) ;
mp 238–242 °C (fusion); [α] = +84° (c 0.10, CH OH). Anal. (C H ClN O ꢂ0.25 H O) C, H,
D
3
22 35
2
2
2
N.
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclopentylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (13) Hydrochloride. A solution of DCC (76 mg, 0.37
mmol) in THF (1 mL) was added to a solution of HOBt (46 mg, 0.33 mmol) and 7ꢀhydroxyꢀBocꢀ
DꢀTicꢀOH (94 mg, 0.32 mmol) in THF (2 mL). After 1 h, the amine 29c hydrochloride (55.8 mg,
0.29 mmol) and NEt (0.125 mL, 0.90 mmol) were added to the suspension. The reaction
3
mixture was stirred at room temperature overnight. The solids were separated by filtration, and
the filtrate concentrated to a residue. The residue was subjected to chromatography on silica gel
eluting with a gradient of 0–50% EtOAc in hexanes. The fractions containing product 31 were
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1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
4
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4
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5
5
6
concentrated and the residue dissolved in CH CN (5 mL) and treated with 4 N HCl in dioxane (5
3
mL). After 1 h, the solution was concentrated, and the residue was subjected to chromatography
1
on silica gel eluting with a gradient of 0–100% EtOAc in hexanes to afford the freebase 13: H
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
NMR (300 MHz, CD OD) δ 8.12 (d, J = 9.23 Hz, 1H), 7.09 (d, J = 8.48 Hz, 1H), 6.75 (dd, J =
3
2
.35, 8.38 Hz, 1H), 6.64 (d, J = 2.26 Hz, 1H), 4.34 (d, J = 4.14 Hz, 2H), 4.15 (dd, J = 4.71, 11.87
Hz, 1H), 3.76–3.92 (m, 1H), 3.23–3.37 (m, 2H), 3.10 (d, J = 11.87 Hz, 1H), 1.38–1.94 (m, 11H),
1
3
1
1
3
.01–1.20 (m, 2H), 0.92 (d, J = 6.59 Hz, 6H); C NMR (75 MHz, CD OD) δ 169.5, 169.4,
3
58.1, 131.1, 129.8, 122.1, 116.9, 113.7, 56.9, 55.6, 55.5, 45.5, 39.1, 39.1, 38.4, 34.2, 34.0, 33.4,
0.9, 26.1, 26.0, 19.8, 18.2. The freebase was converted into the hydrochloride salt to afford 56.6
+
mg (51% over two steps) of a white powder: MS (ESI) m/z 331.6 (M + H) ; mp 142–146 °C
(
fusion); [α] = +99° (c 0.20, CH OH). Anal. (C H ClN O ꢂ0.75 H O) C, H, N.
D 3 20 31 2 2 2
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cycloheptylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (14) Hydrochloride. A solution of DCC (62 mg, 0.30
mmol) in THF (1 mL) was added to a solution of HOBt (38 mg, 0.28 mmol) and 7ꢀhydroxyꢀBocꢀ
DꢀTicꢀOH (76 mg, 0.26 mmol) in THF (2 mL). After 1 h, the amine 29e (135 mg, 0.61 mmol)
and NEt (0.1 mL, 0.72 mmol) were added to the suspension. The reaction mixture was stirred at
3
room temperature for 3 h. The solids were separated by filtration, and the filtrate concentrated to
a residue. The residue was subjected to chromatography on silica gel eluting with a gradient of
0
–100% EtOAc in hexanes. The product containing fractions were concentrated and the residue
dissolved in CH CN (10 mL) and treated with 4 N HCl in dioxane (4 mL). After 1 h, the solution
3
was concentrated, and the residue partitioned between EtOAc and sat. NaHCO . The organic
3
layer was dried (Na SO ) and concentrated. The residue was subjected to chromatography on
2
4
1
silica gel eluting with a gradient EtOAc in hexanes to afford the 14 freebase: H NMR (300
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9
MHz, CDCl ) δ 6.78–7.04 (m, 2H), 6.61 (dd, J = 2.17, 8.19 Hz, 1H), 6.49 (d, J = 1.70 Hz, 1H),
3
3
.71–3.96 (m, 3H), 3.50 (dd, J = 5.09, 10.17 Hz, 1H), 3.06 (dd, J = 5.09, 16.01 Hz, 1H), 2.67
13
(dd, J = 10.17, 16.01 Hz, 1H), 1.57–1.74 (m, 2H), 0.94–1.57 (m, 13H), 0.74–0.87 (m, 6H); C
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
NMR (75 MHz, CDCl ) δ 173.0, 154.9, 136.4, 130.0, 125.3, 114.3, 112.3, 56.8, 51.7, 47.3, 40.3,
3
3
5.9, 35.8, 33.4, 32.4, 30.7, 28.6, 28.4, 26.4, 26.1, 19.2, 17.7. The freebase was converted into
the hydrochloride salt to afford 23.1 mg (23% over two steps) of a white powder: MS (ESI) m/z
+
3
59.4 (M + H) ; mp 138–142 °C (fusion); [α]D = +84° (c 0.10, CH OH). Anal.
3
(
C H ClN O ꢂH O) C, H, N.
22 35 2 2 2
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclobutylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (15) Hydrochloride. A solution of the amine 37
hydrochloride (250 mg, 1.4 mmol) and 7ꢀhydroxyꢀBocꢀDꢀTicꢀOH (154 mg, 0.5 mmol) in THF (5
mL) was treated with T3P (50 wt.% in EtOAc, 0.9 mL) and diisopropylethylamine (0.5 mL) in
an ice bath. The reaction mixture warmed to room temperature overnight then was partitioned
between sat. NaHCO (aq) and EtOAc. The aqueous layer was extracted with EtOAc and the
3
combine organic layers were washed with water, then dried (Na SO ) and concentrated. The
2
4
resulting residue was subjected to chromatography on silica gel eluting with a gradient of 0–50%
EtOAc in hexanes to afford 120.2 mg (58%) of the desired Bocꢀprotected product. Acetyl
chloride (0.5 mL) was added to CH OH (2.5 mL) at –50 °C and the resulting solution was
3
allowed to warm to 0 °C. A solution of the Bocꢀprotected compound (120.2 mg, 0.29 mmol) in
CH OH (2.5 mL) was then added to the HCl solution at –50 °C. External cooling was removed
3
then the reaction mixture was concentrated, the residue was dissolved in fresh CH OH and then
3
concentrated, then concentrated again from EtOAc to afford 100 mg (quantitative yield) of 15
hydrochloride as a white solid. A sample of the hydrochloride salt was converted to the freebase
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1
1
1
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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
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4
4
4
4
4
4
4
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5
5
5
5
5
5
5
5
5
6
1
for NMR characterization: H NMR (300 MHz, CD OD) δ 6.94 (d, J = 8.29 Hz, 1H), 6.55–6.68
3
(
m, 1H), 6.50 (s, 1H), 3.95 (s, 1H), 3.65 (td, J = 4.69, 9.65 Hz, 1H), 3.56 (dd, J = 4.80, 10.27 Hz,
1H), 2.70–2.99 (m, 2H), 2.14–2.38 (m, 1H), 1.94–2.11 (m, 2H), 1.39–1.93 (m, 8H), 0.89 (dd, J =
1
3
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
3
1
.49, 6.69 Hz, 6H); C NMR (126 MHz, CD OD) δ 175.0, 157.1, 136.9, 130.9, 125.5, 115.2,
3
13.3, 58.1, 54.0, 47.8, 40.2, 34.8, 33.8, 32.7, 29.7, 29.6, 19.9, 19.5, 18.4. The compound was
+
further characterized as the hydrochloride salt: MS (ESI) m/z 317.3 (M + H) ; mp begins at 115
°
C (fusion); [α] = +102° (c 0.10, CH OH). Anal. (C H ClN O ꢂ0.5 H O) C, H, N.
D 3 19 29 2 2 2
3
(
3R)ꢀN ꢀ[(1R)ꢀ1ꢀ(Cyclopentylmethyl)ꢀ2ꢀmethylpropyl]ꢀ1,2,3,4ꢀtetrahydroisoquinolineꢀ3,7ꢀ
dicarboxamide (16) Hydrochloride. The Bocꢀprotected compound (33) (55.4 mg, 0.12 mmol)
was dissolved in CH CN (5 mL) and treated with HCl (4 N in dioxane, 4 mL). After 1 h, the
3
reaction mixture was concentrated and the residue subjected to chromatography on silica gel
eluting with a gradient of 0–50% DMA80 in CH Cl to afford 37.7 mg (88%) of the desired 16
2
2
1
freebase: H NMR (300 MHz, CD OD) δ 7.53–7.73 (m, 2H), 7.22 (d, J = 7.91 Hz, 1H), 3.94–
3
4
2
6
5
.18 (m, 2H), 3.76 (dd, J = 4.43, 9.70 Hz, 1H), 3.66 (dd, J = 5.09, 9.61 Hz, 1H), 2.82–3.14 (m,
H), 1.85–1.96 (m, 3H), 1.29–1.84 (m, 10H), 0.97–1.17 (m, 2H), 0.91 (dd, J = 3.01, 6.78 Hz,
1
3
H); C NMR (75 MHz, CD OD) δ 174.6, 172.1, 139.4, 136.6, 133.0, 130.1, 126.8, 126.4, 57.2,
3
4.8, 47.4, 39.2, 38.3, 34.3, 34.0, 33.4, 33.1, 26.1, 26.0, 19.8, 18.3. The freebase was converted
+
into the hydrochloride salt to afford a pale yellow powder: MS (ESI) m/z 358.2 (M + H) ; mp
1
53–157 °C (fusion); [α] = +98° (c 0.10, CH OH). Anal. (C H ClN O ꢂH O) C, H, N.
D 3 21 32 3 2 2
(3R)ꢀNꢀ[(1R)ꢀ2ꢀCyclopentylꢀ1ꢀcyclopropylethyl]ꢀ7ꢀhydroxyꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (17) Hydrochloride. To a rapidly stirring solution of
DCC (0.66 g, 3.2 mmol) and HOBt (0.36 g, 2.6 mmol) in THF (7.5 mL) was added 7ꢀhydroxyꢀ
BocꢀDꢀTicꢀOH (752 g, 2.5 mmol). After 1 h, the amine 29d hydrochloride (519 mg, 2.7 mmol)
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was converted to the freebase, dissolved in THF (2.5 mL), and added to the suspension. The
reaction mixture was stirred at room temperature for 12 h. The solids were separated by filtration
and the filtrate concentrated to a residue. The residue was subjected to chromatography on silica
gel eluting with a gradient of 0–5% isopropanol in CH Cl to afford 1.03 g (96%) of the Bocꢀ
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
2
2
protected intermediate as a white foam. A cold volume of methanol (5 mL) was treated with
acetyl chloride (1 mL) at –78 °C then allowed to warm to room temperature. The solution was
chilled before the addition of a sample of the Bocꢀprotected compound (253 mg, 0.59 mmol),
prepared above, in methanol (5 mL). After 12 h under a stream of nitrogen, the solids were reꢀ
dissolved in a minimum of methanol and diluted with EtOAc. A small addition of hexanes
initiated crystallization. The solids were collected and dried to afford 197 mg (92%) of the
1
desired 17 hydrochloride salt as a white crystalline solid: H NMR (300 MHz, CD OD) δ 8.32
3
(d, J = 9.04 Hz, 1H), 7.10 (d, J = 8.29 Hz, 1H), 6.76 (dd, J = 1.98, 8.38 Hz, 1H), 6.65 (s, 1H),
4.24–4.44 (m, 2H), 4.03–4.19 (m, 1H), 3.19–3.55 (m, 2H), 2.99–3.14 (m, 1H), 1.02–2.06 (m,
1
3H), 0.82–1.01 (m, 1H), 0.56 (dt, J = 4.99, 8.62 Hz, 1H), 0.45 (dt, J = 3.86, 8.52 Hz, 1H), 0.14–
0
.37 (m, 2H); mp 145–150 °C; [α] = +78° (c 0.10, CH OH). Anal. (C H ClN Oꢂ0.5 H O) C,
D
3
20 29
2
2
H, N.
(3R)ꢀ7ꢀHydroxyꢀNꢀ{(1R)ꢀ2ꢀmethylꢀ1ꢀ[(4ꢀmethylcyclohexyl)methyl]propyl}ꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (18) Hydrochloride. To a rapidly stirring solution of
DCC (0.66 g, 3.2 mmol) and HOBt (0.33 g, 2.5 mmol) in THF (7.5 mL) was added 7ꢀhydroxyꢀ
BocꢀDꢀTicꢀOH (600 mg, 2.0 mmol). After 1 h, the freebase amine 41 (419 mg, 2.3 mmol) in
THF (2.5 mL) was added to the suspension. The reaction mixture was stirred at room
temperature for 12 h. The solids were separated by filtration and the filtrate concentrated to a
residue. The residue was subjected to chromatography on silica gel to afford the Bocꢀprotected
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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
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5
6
intermediate, which was treated with a solution of methanoic HCl (10 mL) prepared from acetyl
chloride (1 mL). The solvent was concentrated to afford 236 mg (60%) of the 18 hydrochloride
salt. A sample of the hydrochloride salt was converted into the freebase for NMR
1
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
characterization: H NMR (300 MHz, CD OD) δ 8.12 (d, J = 9.04 Hz, 1H), 7.09 (d, J = 8.29 Hz,
3
1
1
1
1
3
H), 6.75 (d, J = 7.54 Hz, 1H), 6.65 (s, 1H), 4.24–4.45 (m, 2H), 4.17 (dd, J = 4.62, 11.77 Hz,
H), 3.81–4.00 (m, 1H), 3.48 (q, J = 7.10 Hz, 1H), 2.98–3.17 (m, 1H), 1.91 (d, J = 7.54 Hz, 1H),
1
3
.61–1.82 (m, 4H), 1.08–1.59 (m, 7H), 0.75–1.07 (m, 12H); C NMR (75 MHz, CD OD) δ
3
68.0, 156.6, 129.7, 128.3, 120.6, 115.4, 112.2, 55.4, 55.4, 52.1, 52.0, 44.0, 39.0, 38.9, 35.0,
4.8, 33.9, 33.9, 32.6, 32.5, 32.1, 29.4, 21.6, 18.3, 16.7. The compound was further characterized
+
as the hydrochloride salt: mp 173–177 °C (fusion); MS (ESI) m/z 459.4 [M+H] ; [α] = +94.2°
D
(
c 1.00, CH OH). Anal. (C H ClN O ꢂ0.5 H O) C, H, N.
3 22 35 2 2 2
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclohexylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ2ꢀmethylꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (19) Hydrochloride. A sample of 1 hydrochloride (60
mg, 0.16 mmol) in 1,2ꢀdichloroethane (1.6 mL) was treated with 37% formaldehyde (0.1 mL, 1.3
mmol) and NaBH(OAc) (170 mg, 0.8 mmol). The sealed vial was left to stir for 72 h. The
3
reaction mixture was then diluted with CH Cl and dried with Na SO . The solids were separated
2
2
2
4
by filtration and washed with EtOAc. The filtrates and washing were combined and
concentrated. The residue was subjected to chromatography on silica gel eluting with a gradient
1
of 0–75% EtOAc in hexanes to afford 54.4 mg (95%) of the 19 freebase: H NMR (300 MHz,
CDCl ) δ 8.10 (br. s., 1H), 7.20–7.33 (m, 1H), 6.94 (d, J = 8.10 Hz, 1H), 6.72 (dd, J = 2.26, 8.10
3
Hz, 1H), 6.60 (d, J = 2.07 Hz, 1H), 3.82–3.95 (m, 1H), 3.60–3.82 (m, 2H), 3.39 (t, J = 6.78 Hz,
1
H), 2.90–3.11 (m, 2H), 2.50 (s, 3H), 1.53–1.83 (m, 4H), 1.46 (d, J = 12.24 Hz, 1H), 1.03–1.34
1
3
(m, 6H), 0.61–0.99 (m, 9H); C NMR (75 MHz, CDCl ) δ 172.4, 155.3, 135.0, 128.9, 124.1,
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14.6, 113.0, 64.2, 55.3, 51.2, 42.2, 39.4, 34.2, 34.2, 32.5, 32.3, 28.9, 26.5, 26.2, 26.0, 19.1, 17.7.
The freebase was converted into the hydrochloride salt as a white powder: MS (ESI) m/z 359.5
+
(M + H) ; mp 248–250 °C (fusion); [α] = +105° (c 0.10, CH OH). Anal. (C H ClN O ) C, H,
D
3
22 35
2
2
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
N.
(3R)ꢀNꢀ[(1R)ꢀ1ꢀ(Cyclopentylmethyl)ꢀ2ꢀmethylpropyl]ꢀ7ꢀhydroxyꢀ3ꢀmethylꢀ1,2,3,4ꢀ
tetrahydroisoquinolineꢀ3ꢀcarboxamide (20) Hydrochloride. A solution of DCC (132 mg, 0.64
mmol) in THF (2.5 mL) was added to a solution of HOBt (83 mg, 0.62 mmol) and 7ꢀmethoxyꢀ3ꢀ
22
methylꢀBocꢀDꢀTicꢀOH (172 mg, 0.54 mmol) in THF (3 mL). After 1 h, the amine 29c (127 mg,
0
.66 mmol) and NEt (0.30 mL, 2.0 mmol) were added to the suspension. The reaction mixture
3
was stirred at room temperature for 12 h. The solids were separated by filtration, and the filtrate
concentrated to a residue. The residue was subjected to chromatography on silica gel eluting with
a gradient of 0–40% EtOAc in hexanes. The product containing fractions were concentrated and
the residue dissolved in CH Cl (5 mL), cooled to –78 °C and treated with BBr (4 mL, 1.0 M in
2
2
3
CH Cl ) and left to warm to room temperature. After 12 h, the solution was cooled then
2
2
quenched with CH OH and concentrated. The residue was partitioned between CH Cl and sat.
3
2
2
NaHCO (aq). The organic layer was dried (Na SO ) and concentrated. The residue was
3
2
4
subjected to chromatography on silica gel eluting with a gradient of 0–100% EtOAc in hexanes
1
to afford the 20 freebase: H NMR (300 MHz, CDCl ) δ 7.38 (d, J = 9.98 Hz, 1H), 6.95 (d, J =
3
8
.10 Hz, 1H), 6.69 (dd, J = 2.35, 8.19 Hz, 1H), 6.61 (d, J = 2.07 Hz, 1H), 3.97 (s, 1H), 3.78–3.88
(m, 1H), 3.63–3.78 (m, 1H), 3.08 (d, J = 15.64 Hz, 1H), 2.74 (d, J = 15.45 Hz, 1H), 1.57–1.79
13
(m, 3H), 1.27–1.56 (m, 10H), 0.89–1.10 (m, 2H), 0.84 (dd, J = 5.37, 6.69 Hz, 6H); C NMR (75
MHz, CDCl ) d 176.1, 155.2, 136.4, 129.7, 125.3, 114.1, 112.2, 58.5, 53.1, 45.2, 38.5, 37.0,
3
36.4, 33.3, 32.4, 26.6, 25.1, 25.0, 19.2, 17.5. The freebase was converted into the hydrochloride
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