Structure activity relationships of new inhibitors of mammalian 2,3-oxidosqualene cyclase designed from isoquinoline derivatives

Article abstract of DOI:10.1248/cpb.50.316

We have designed more potent inhibitors from the previously reported LF 05-0038, a 6-isoquinolinol based inhibitor of 2,3-oxidosqualene cyclase (IC ₅₀: 1.1 μM). Replacement of the 3-OH group by various 3-substituted amino groups, and modification of the alkyl chain borne by the endocyclic nitrogen led to inhibitors with IC₅₀ in the range of 0.15 to 1 μM. In a second step, opening of the bicyclic ring system afforded the corresponding aminoalkylpiperidines which were slightly more potent. Finally, introduction of suitable aromatic containing moieties on the piperidine nitrogen yielded very potent inhibitors such as 20x (IC₅₀=18 nM) easy to synthesize and achiral. The recent availability of the crystal structure of squalene-hopene cyclase allowed us to construct a three-dimensional (3D) model of the related 2,3-oxidosqualene cyclase (OSC) which was tentatively used to describe the possible mode of binding of our compounds and which can be useful for designing new inhibitors.

Full text of DOI:10.1248/cpb.50.316

316
Chem. Pharm. Bull. 50(3) 316—329 (2002)
Vol. 50, No. 3
Structure Activity Relationships of New Inhibitors of Mammalian
2,3-Oxidosqualene Cyclase Designed from Isoquinoline Derivatives
Jean BINET, Didier THOMAS, Abdellah BENMBAREK, Daniel de FORNEL, and Patrice RENAUT*
Laboratoires Fournier S.A., 50 rue de Dijon, 21121 Daix, France.
Received September 14, 2001; accepted December 21, 2001
We have designed more potent inhibitors from the previously reported LF 05-0038, a 6-isoquinolinol based
inhibitor of 2,3-oxidosqualene cyclase (IC50: 1.1 mM). Replacement of the 3-OH group by various 3-substituted
amino groups, and modification of the alkyl chain borne by the endocyclic nitrogen led to inhibitors with IC50 in
the range of 0.15 to 1 mM. In a second step, opening of the bicyclic ring system afforded the corresponding
aminoalkylpiperidines which were slightly more potent. Finally, introduction of suitable aromatic containing
moieties on the piperidine nitrogen yielded very potent inhibitors such as 20x (IC50؍18 nM) easy to synthesize
and achiral. The recent availability of the crystal structure of squalene-hopene cyclase allowed us to construct a
three-dimensional (3D) model of the related 2,3-oxidosqualene cyclase (OSC) which was tentatively used to de-
scribe the possible mode of binding of our compounds and which can be useful for designing new inhibitors.
Key words 2,3-oxidosqualene cyclase inhibitor; 6-isoquinolineamine; aminoalkylpiperidine; squalene-hopene cyclase; 3D
model
Inhibition of 2,3-oxidosqualene cyclase (OSC; EC present our efforts based on previous results, to obtain new
5.4.99.7) is an interesting target for the design of new hypo- potent and easily accessible inhibitors of OSC.
cholesterolemic drugs useful for the prevention of cardiovas-
cular diseases.1) OSC catalyzes the conversion of (S)-2,3-oxi- Chemistry
dosqualene to lanosterol which is probably one of the most
The synthetic route to the key intermediates leading to the
complex enzymatic reaction described so far. A huge number compounds listed in Tables 1 and 2 is shown in Chart 1. Re-
of studies have been devoted to the elucidation of its mecha- ductive amination of the carbonyl compounds 1a—c6) with
nism of action for more than four decades.2) Although either NH4OAc and NaBH3CN8) in CH3OH provided amino deriva-
kinetic or structural approaches have been recently describ- tives which were acylated using TFAA in THF. Chromato-
ed,3) none of them is really able to give a full picture of the graphic separation of the isomers afforded b and a isomers
cyclisation/rearrangement process. In this perspective, crys- 2a—c and 3a, b in a 85/15 ratio. Assignments of the stereo-
1
tallographic study of this enzyme could be very helpful but chemistry of 2a—c and 3a, b were made by H-NMR analy-
has still to be performed. However, the crystal structure of a sis using the chemical shift of the proton borne by C-6.9) De-
closely-related enzyme: squalene-hopene cyclase, has been protection of the trifluoroacetyl group was carried out with
recently determined.4) Moreover, the photolabeling of this K2CO3 in refluxing aqueous CH3OH (Method A).
enzyme5a,b) with [3H]Ro48-8071, a molecule known as a po-
Deprotection of the N-Boc group of 2c (Chart 2) was
tent inhibitor of both lanosterol synthase and squalene- achieved in a conventional way with 3 N HCl in CH3OH to
hopene cyclase, has also shed some light on this issue. Fi- afford 6 which was alkylated with n-bromododecane in
nally an important review5c) on the mechanistic aspects of the CH3CN (Method B). Compound 7 was deprotected using
synthesis of polycyclic triterpene gives a general picture on method A to obtain 8a. Preparation of 8d was achieved using
the role of the enzyme in protecting the intermediate carbo- CH3I as alkylating agent with NaH in N,N-dimethylform-
cations against addition of water allowing the polycyclisation amide (DMF) followed by hydrolysis of the trifluoroacetyl
to proceed. We recently described inhibitors of OSC6) based moiety. The synthetic route to 8b, c, e—h is shown in Chart
on the 6-isoquinolinol structure. This template which is sup- 3. The intermediates 4a and 5b were converted to 9a and 10b
posed to mimic a postulated pro-C8 carbocation intermediate by reductive alkylation with HCHO and NaBH3CN (Method
I (Fig. 1) along the cyclisation-rearrangement pathway to C).10) Removal of the protective groups of 9a and 10b was
lanosterol, was initially developed by Rahier and co- achieved by either hydrogenolysis for 9a or the Olah’s
workers.7) Our study focused on the investigation of the method11) for 10b to afford 11 and 12, respectively. Alkyla-
structural requirements of 6-isoquinolinol-based inhibitors tion of 12 with n-bromododecane in CH3CN (Method B) af-
for OSC inhibition. Unfortunately, the obtained inhibitors re- forded 8b. The isoquinolines 8c, e—h were obtained by ei-
mained synthetically poorly accessible due to the presence of ther alkylation using 1-bromo-6,6-dimethyl-2-hepten-4-yne
several chiral centers. Nevertheless, we have determined or a reductive alkylation when aldehydes or ketones were
some important features that can be used for the design of commercially available (Method D), or by a two-step proce-
more readily accessible molecules. In this publication, we dure involving the formation of an amide followed by reduc-
tion with Red-Al (Method E). The preparation of piperidi-
neethanamine derivatives (Tables 3, 5) is illustrated in Charts
4—6. Aldol condensation between 4-piperidone 13 and ethyl
isobutyrate in the presence of lithium diisopropylamide
(LDA) led to 4-hydroxy-piperidine12) 14 which was subse-
Fig. 1. Postulated pro-C8 Carbocation Intermediate I
quently dehydrated with SOCl2 in CHCl3 to give 15 (Chart
To whom correspondence should be addressed. e-mail: p.renaut@fournier.fr
© 2002 Pharmaceutical Society of Japan

March 2002
317
Reagents: (a) NH4OAc, NaBH3CN, MeOH; (b) TFAA, Et3N, THF; (c) chromatographic separation; (d) K2CO3, MeOH, H2O, reflux.
Chart 1
Reagents: (a) 3 N HCl, MeOH; (b) n-C12H25Br, K2CO3, CH3CN; (c) NaH, CH3I, DMF then K2CO3, MeOH, H2O, reflux.
Chart 2
Reagents: (a) HCHO, NaBH3CN, MeOH; (b) H2, Pd/C, AcOH; (c) R2COR3, NaBH3CN, MeOH; (d) R4COOH, CDI, THF then Red-Al®, toluene; (e) R1Br, K2CO3, CH3CN; (f)
Me3SiCl, NaI, CH3CN.
Chart 3
Reagents: (a) LDA, (CH3)2CHCOOEt, THF, Ϫ50 °C; (b) SOCl2, CHCl3, cat DMF; (c) 80 atm H2, Pd/C, MeOH, 70 °C; (d) NaOH, EtOH, H2O then 5 N HCl; (e) SOCl2; (f)
R2R3NH; (g) Red-Al®, toluene, reflux; (h) Ac2O, Et3N, CH2Cl2.
Chart 4

318
Vol. 50, No. 3
Reagents: (a) R2R3NH, HCHO, AcOH; (b) PtO2, AcOH, H2 45 psi, 60 °C.
Chart 5
Reagents: (a) N2H4·H2O, EtOH; (b) Me2CH(CH2)3COCl, Et3N, CH2Cl2; (c) H2, Pd/C, MeOH; (d) CH3I, Et2O; (e) Me2CH(CH2)3NH2, toluene, reflux.
Chart 6
Reagents: (a) acrylonitrile, Triton B, tert-BuOH; (b) Raney Ni, EtOH, NH3, 50 °C, H2 50 psi; (c) H2, PtO2, AcOH then NaOH; (d) LiAlH4, THF; (e) HCOOH, HCHO.
Chart 7

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319
25.14) Hydrogenation of 25 and simultaneous cyclization of
the resulting amino ester was performed in a Parr apparatus
with Raney nickel as catalyst and afforded 26 in good yield.
Catalytic hydrogenation of the pyridine ring of 26 with PtO2
in AcOH followed by alkylation of the resulting compound
27 yielded 28. Reduction of the piperidone 28 with LiAlH4
led to 21a. This compound was finally methylated following
Eschweiler–Clarke15a—c) procedure to provide 21b.
4). Hydrogenation of the double bond and hydrogenolysis of
the benzyl group of 15 proceeded in one step with 5% Pd/C
as catalyst under 80 atm H2 pressure to afford 16. Alkylation
of 16 gave 17 which was hydrolyzed with NaOH to afford
18. Reaction of acid 18 with SOCl2 followed by condensa-
tion of the resulting acid chloride with various amines, af-
forded amide derivatives 19a—f, j, k (Method F) which were
reduced with Red-Al (Method G). An alternative original
three-step synthesis has been developed for the preparation
of 20i, l, m, p, s, u—ab (Chart 5) which involved a Mannich
reaction (Method H)13a,b) between commercially available 4-
isopropylpyridine, formaldehyde and secondary amines in
the first step. Hydrogenation of the pyridine ring with PtO2 as
catalyst in the second step was followed by alkylation of the
resulting piperidine derivatives using methods B, D or E. The
preparation of compounds 20n, o, q, r, t was performed fol-
lowing the pathways described in Chart 6. Hydrazinolysis of
20ac and subsequent acylation of the resulting amine with 5-
methyl hexanoyl chloride in CH2Cl2 in the presence of Et3N
gave 20o. Compound 20n was prepared by hydrogenation of
the unsaturated bonds of 20p with Pd/C as catalyst. Quater-
nary ammonium salt 20t was obtained by reacting 20s with
CH3I in ether. Refluxing 20ad with 4-methyl pentaneamine
in toluene gave 20q which was reduced following Method G.
Preparation of bipiperidine derivatives (Table 4) is shown in
Chart 7. Michael addition of acrylonitrile with 24 afforded
Results and Discussion
OSC inhibition was measured using rat liver microsomes
and synthetic (R,S)-2,3-oxidosqualene. The inhibition poten-
cies were expressed as IC50 values. The 6-isoquinolinol de-
rivative LF 05-0038 (see Table 1)6) was designed as a mimic
of the postulated pro-C8 carbocation intermediate I along the
cyclisation-rearrangement pathway, i.e. the second intermedi-
ate step of the 2,3-oxidosqualene cyclization (Fig. 1). The
hydroxyl group of 6-isoquinolinol was the equivalent of the
hydroxyl group of the A ring system in the intermediate I.
On the other hand, the positive charge borne by the proto-
nated nitrogen was supposed to mimic the C-8 carbocation of
I. Most of the results obtained with various analogues were
consistent with this hypothesis.6) In this study we turned our
attention to several features of the 6-isoquinolinol derivatives
with the aim of finding synthetically more accessible in-
hibitors with more drug-like structures. We first investigated
Table 1. 1,2,3,5,6,7,8,8a-Octahydro-5,5,8a-trimethyl-6-isoquinolineamine Derivatives
Compd.
R1
R2
mp, °C
Yield, % (Method)
Formulaa)
OSC inh IC50 mM
LF05-0038d)
OH
NH2
H
NMe2
NHMe
H
H
NMe2
H
H
1.1
85
5.7
0.44
25
b)
8a
8b
8c
8d
170
139
193
130
75 (A)
34 (D)
80 (C)
47 (A)
C24H46N2·C4H4O4
c)
C26H50N2·2C2H2O4b)
C26H50N2·3C4H4O4
c)
C25H48N2·C2H2O4
a) Analytical results are within Ϯ0.4% of theoretical values unless otherwise noted. b) Fumarate. c) Oxalate. d) Reference 6.
Table 2. N,N-Dimethyl-1,2,3,5,6,7,8,8a-Octahydro-5,5,8a-trimethyl-6-isoquinolineamine Derivatives
Compd.
8c
R1
mp, °C
193
Yield, % (Method)
74 (D)
Formulaa)
OSC inh IC50 mM
b)
n-C12H25
C26H50N2·3C4H4O4
0.44
0.23
b)
8e
142
41 (D)
C27H44N2·C4H4O4
8f
oil
26 (B)
59 (E)
C23H38N2
0.26
0.15
8g
210
C23H34N2·2C7H8O3Sc)
d)
8h
150
95 (E)
C29H38N2·2C2H2O4
0.32
a) Analytical results are within Ϯ0.4% of theoretical values unless otherwise noted. b) Fumarate. c) Tosylate. d) Oxalate.

320
Vol. 50, No. 3
Table 3. b,b-Dimethyl-1-dodecyl-4-piperidineethanamine Derivatives
Compd.
R2
R3
mp, °C
Yield, % (Method)
Formulaa)
OSC inh IC50 mM
b)
20a
20b
20c
20d
20e
20f
20g
20h
20i
H
Me
Et
H
H
H
H
H
H
Me
H
Me
Et
Bn
100
139
160
186
114
174
102
113
132
108
124
129
64 (G)
79 (G)
100 (G)
95 (G)
80 (G)
95 (G)
97
C21H44N2·C4H4O4
7.1
0.34
0.66
Ͼ50
55
Ͼ50
18.9
14.3
0.12
13.7
Ͼ50
35
C22H46N2·2C7H8O3bS)d)
C23H48N2·2C4H4O4
b)
Pr
C24H50N2·C4H4O4
i-Pr
Bn
Ac
Ac
Me
Et
C24H50N2·2C7H8O3bS)d)
C28H50N2·2C4H4O4
C24H48N2O·C7H8O3bS)d)
C23H46N2O·C4H4O4
86
b)
100 (B)
85 (G)
82 (G)
70 (D)
C23H48N2·2C4H4O4b)
20j
20k
20l
C25H52N2·2C4H4O4
b)
Me
C29H52N2·C4H4O4
c)
(CH2)5
C26H52N2·2C4H4O4
a) Analytical results are within Ϯ0.4% of theoretical values unless otherwise noted. b) Fumarate. c) Maleate. d) Tosylate.
Table 4. 3-[4-(1-Dodecylpiperidinyl)]piperidine Derivatives
piperidineethanamine derivatives.19) We have indeed shown
in a previous study,6) that the angular methyl group was not
necessary for the activity. The flexibility brought by the ring
opening seems to be favorable to the activity as shown by the
resulting primary amine 20a found to be about ten-fold more
potent than the corresponding bicyclic analogue 8a. We then
investigated in details the influence of the substituents borne
by the terminal nitrogen atom. Among the secondary amines,
the smaller the substituent was, the better the activity: the
IC50 was 0.34 mM for 20b, 0.66 mM for 20c and Ͼ50 mM for
20d—f. The same trend was observed with tertiary amines,
where the best activity, similarly to the bicyclic series, was
observed for the dimethyl derivative 20i (IC50ϭ0.12 mM). Fi-
OSC inh
IC50 mM
Compd.
R
mp, °C Yield, %
Formulaa)
21a
21b
H
Me
176
160
97
95
C22H44N2·2C7H8O3Sb) Ͼ50
C23H46N2·2C7H8O3Sb)
42
a) Analytical results are within Ϯ0.4% of theoretical values unless otherwise noted.
b) Tosylate.
the importance of the hydroxyl group. Indeed, the cyclization nally, we synthesized the amides 20g and 20h.
process mediated by the enzyme is triggered by the protona-
The decrease of activity observed between 20h and 20c
tion of the epoxide and the proton donor is very likely the seems to be consistent with the existence of an ionic interac-
Asp456.5c,20) We thus introduced several types of amine in tion. The last structural change made on this part of the mol-
place of the hydroxyl group in order to increase the affinity ecule was the insertion of the nitrogen atom in a ring, result-
for the active site by the putative resulting ionic interaction ing into two 3-(piperidinyl)-piperidine derivatives 21a and
with the Asp456. A similar approach was fruitful in the case 21b (Table 4). This new constraint proved to be detrimental
of squalene based inhibitors.1b) Table 1 shows that the pri- to the activity: 21a, which can be viewed as a rigid analogue
mary amine 8a is much less active than the parent hydroxy- of the active compound 20c, was found inactive (i.e. IC50Ͼ
lated analogue. However, the corresponding dimethylated ter- 50 mM) whereas the corresponding methylated analogue 21b
tiary amine 8c18) is about two orders of magnitude more po- proved to be a weak inhibitor. A similar structure activity re-
tent than the primary amine 8a and about two-fold more po- lationship has been published for azasqualene based in-
tent than the corresponding hydroxylated compound. As pre- hibitors of pea seedlings and rat liver OSC.24)
viously observed for the corresponding a-hydroxylated ana-
Having optimized the core structure i.e. a b,b-dimethyl-4-
logue,6) the a-isomer 8b is about ten-fold less active than the piperidineethanamine, we then studied different replacements
b-isomer 8c. The monomethyl derivative 8d is fifty-fold less of the saturated dodecyl chain (Table 5). In our previous
active than the dimethyl derivative 8c. These results are con- work, we found that the optimal carbon chain length corre-
sistent with the formation of an ionic interaction with the sponded to a 10 to 12 carbon unit substituent. In the present
Asp456 although the part played by the methyl groups is still study we confirmed that a very short chain (a methyl group)
unclear. Table 2 presents a few derivatives in which the satu- led to an inactive compound 20m. The branched chain of
rated dodecyl chain was replaced by various unsaturated sub- terbinafine led to an active compound 20p. Its complete re-
stituents intended to better mimic the terpenic chain of the duction afforded 20n showing the same activity. In contrast,
natural substrate. The chains supposed to mimic the squale- introduction of polar functions such as amides or amines in
noid moiety encountered in terbinafine25) and naftifine,26) led the chain afforded weak inhibitors: 20o and 20r, except 20q
to more potent compounds 8f and 8g. In order to simplify the which is rather active. As previously observed6,16) in related
core of these inhibitors, we opened the ring, mimicking the A series, the conversion of the tertiary amine of 20i into a ter-
ring system of the pro-C8 carbocation intermediate I,17) and tiary amide afforded an almost equipotent derivative 20s. In
removed the angular methyl group leading to the achiral 4- contrast, the quaternarisation of the amine of this derivative

March 2002
321
Table 5. b,b-Dimethyl-N,N-dimethyl-4-piperidineethanamine Derivatives
Yield, %
(Method)
OSC inh
IC50 mM
Compd.
R1
mp, °C
Formulaa)
c)
20m
20i
20n
20o
Me
n-C12H25
(CH2)5C(CH3)3
(CH2)3NHCO(CH2)3CH(CH3)2
160
132
138
87
100 (B)
100 (B)
100
C12H26N2·2C4H4O4c)
C23H48N2·2C4H4O4c)
C20H42N2·2C4H4O4
C21H43N3O·2C2H2O4
Ͼ50
0.12
0.28
1.9
d)
c)
32
e)
20p
192
56 (B)
C20H36N2·2C2H2O4
0.23
20q
20r
20s
20t
20u
20v
20w
20x
(CH2)3CONH(CH2)3CH(CH3)2
(CH2)4NH(CH2)3CH(CH3)2
CO(CH2)10CH3b)
140
142
138
208
169
150
194
110
71
83 (G)
66
100
52
95 (G)
60
83 (G)
C21H43N3O·2C4H4O4
0.7
18
0.26
1.7
0.76
0.73
0.33
0.018
c)
C21H45N3·3C4H4O4
d)
C23H46N2O·C2H2O4
C24H49IN2O
C20H30N2O·C4H4O4
CO(CH2)10CH3
COCHϭCHC6H5
c)
c)
CH2CHϭCHC6H5
COC(CH3)2OC6H4-4Cl
CH2C(CH3)2OC6H4-4Cl
C20H32N2·2C4H4O4
C21H33ClN2O2·C4H4O4
c)
c)
C21H35ClN2O·2C4H4O4
d)
20y
20z
169
166
58
C25H36N2O2·C2H2O4
41
c)
100 (G)
C25H38N2O·2C4H4O4
0.82
c)
20aa
20ab
COCH(CH3)C6H4-4iBu
CH2CH(CH3)C6H4-4iBu
172
145
74
88 (G)
C24H40N2O·C4H4O4
C24H42N2·2C4H4O4
2.7
0.42
c)
a) Analytical results are within Ϯ0.4% of theoretical values unless otherwise noted. b) Quaternary methylammonium iodide. c) Fumarate. d) Oxalate. e) Maleate.
led to 20t which was six-fold less active. Different com- nitrogen nearby the Asp456 which corresponds to Asp376 in
pounds bearing aromatic containing substituents were then hopene-squalene cyclase. The docking of the two inhibitors
synthesized as amides and their corresponding amines. In 8c and 20x was made starting from this assumption (Figs. 2,
general, the amines proved to be more active than the 3). The cavity surrounding the Asp456 can easily accommo-
amides. For example, 20ab is six-fold more active than 20aa. date one or two methyl groups but not bulkier groups without
This trend culminates with compounds 20w and 20x, this destroying the possible salt bridge. In the case of compound
one being the most potent inhibitor of this series with an IC50 8c, the two methyl groups come in close contact to the aro-
of 0.018 mM.
matic ring of Trp388 (Figs. 2, 3). However a dramatic de-
The publication of the crystal structure of squalene-hopene crease of potency was observed in the piperidine series and
cyclase led us to construct a 3D model of the rat OSC start- with compounds bearing moieties bulkier than the dimethy-
ing from the sequence alignment suggested by Wendt et al.4) lamino group such as 20d, 20e, 20f, 20j, 20k, 20l, 21a and
The conformation of the inserted loops was then deduced 21b. However, this model does not explain the very bad ac-
from similar sequences encountered in proteins structures of tivities of the primary amine 8a and the secondary amine 8d.
the Protein Data Bank according to a well-validated homol- It should not be forgotten that this enzyme is membrane
ogy modeling methodology.21) The amino-acids close to the bound and that the inhibitor, similarly to the substrate,4)
site which triggers the cyclisation, i.e. around the Asp456 (or should diffuse to the active site through the phospholipid bi-
the corresponding Asp376 of the squalene-hopene cyclase), layer. The amount of the inhibitor available at the active site
are well conserved among the two enzymes, except Asp377 is thus depending on the partitioning of the inhibitor between
which is only present in squalene-hopene cyclase.4,5c) This the aqueous phase and the membrane, and a direct analysis
suggests a high similarity of the active sites of the two en- of the structure activity relationships is consequently diffi-
zymes at least in this region. Consequently, although our cult. Fig. 4 shows a possible mode of binding of the best in-
model should be confirmed by further studies, it could be hibitor 20x in the active site of the enzyme. It is worthnoting
tentatively used a posteriori to explain some of the features that the flexibility brought by the opening of the bicycle in-
of the structure activity relationships observed in our series duces a better positioning of the dimethylamino group of this
of inhibitors. The crystal structure of the squalene-hopene derivative towards the Asp456 and Trp388, optimizing ionic
cyclase co-crystallized with a competitive inhibitor: N,NЈ-di- interaction and Van der Waals contacts (the distance between
methyldodecylamine-N-oxide shows that the nitrogen atom the nitrogen of 20x and the closest oxygen of Asp486 is
of this inhibitor is close to the Asp376. It was previously 2.84 Å versus 3.23 Å for 8c). A H-bond between the hydro-
shown6,16) that the 6-isoquinolinol-based inhibitors of OSC gen of the cyclic ammonium and the oxygen of Tyr99 is
behave as competitive inhibitors. In the hypothesis that the made possible with this compound (the distance between the
closely-related amino analogues behave similarly, their bind- corresponding atoms in the case of 8c is 3.99 Å compared to
ing to the active site should position the exocyclic protonated 2.54 Å with 20x). Finally, the 4-chlorophenoxy moiety is lo-

322
Vol. 50, No. 3

March 2002
323
cated in a cavity suitably adapted and highly hydrophobic 1.4845; 1H-NMR (CDCl3) d: 1.08 (3H, s), 1.24 (11H, m), 1.27 (3H, t,
Jϭ5.08 Hz), 1.47 (1H, m), 1.75 (1H, m), 2.21 (1H, m), 2.56 (1H, m), 3.77
where the Phe697 develops a clear T-shape interaction with
(1H, m), 3.95 (1H, m), 4.17 (2H, q, Jϭ5.08 Hz), 4.34 (1H, m), 5.50—5.55
the phenyl of 20x and where the chlorine atom is surrounded
(1H, m), 6.01 (1H, d, Jϭ7.16 Hz).
with aliphatic and aromatic residues (Fig. 5). All these fea-
(6b,8ab)-3,5,6,7,8,8a-Hexahydro-5,5,8a-trimethyl-6-trifluoroacetyl-
tures may explain the high potency of this inhibitor. A closer
look at these docking models could help the design of more
potent inhibitors, for instance, replacing the chlorine atom of
20x by a hydrophobic group such a phenyl which could bring
a supplementary interaction surface. It can be noticed that
halogenated aryl substituents have been successfully intro-
duced in Roche and Karl Thomae OSC inhibitors.1c,d) In con-
clusion, based on a good OSC inhibitor (LF 05-0038) ob-
tained in a previous study, we designed structurally simpler
molecules and found a rather potent inhibitor: 20x. Contrary
to LF 05-0038, this molecule, which is achiral and readily
accessible, deserves further biological tests, in particular in
vivo studies. Furthermore, the recent availability of the crys-
tal structure of hopene-squalene cyclase led us to construct a
3D model of OSC that could help designing new inhibitors
of this enzyme.
amino-2(1H)-isoquinolinecarboxylic Acid 2-Methyl-2-propyl Ester (2c)
1
mp 156 °C; H-NMR (CDCl3) d: 1.08 (3H, s), 1.12 (3H, s), 1.18 (3H, s),
1.34—1.61 (11H, m), 1.73—1.87 (2H, m), 2.48—2.59 (1H, m), 3.64—3.76
(1H, m), 3.79—3.84 (1H, m), 5.52—5.58 (1H, m), 6.13 (1H, d, Jϭ9.5 Hz).
(6b,8ab)-6-Amino-3,5,6,7,8,8a-hexahydro-5,5,8a-trimethyl-2(1H)-iso-
quinolinecarboxylic Acid Phenylmethyl Ester (4a) Method A A mix-
ture of 2a (35 g, 80 mmol), of K2CO3 (115 g, 0.8 mol) in 500 ml of CH3OH
and 100 ml of H2O was refluxed for 8 h. Upon cooling at room temperature,
the mixture was evaporated and the residue was partitioned between EtOAc
and water. The organic solution was washed with water, dried (MgSO4) and
1
concentrated to give 27 g (100%) of 4a. H-NMR (CDCl3) d: 0.99 (3H, s),
1.17—1.28 (8H, m), 1.46—1.67 (3H, m), 2.17 (2H, br s), 2.45—2.61 (1H,
m), 3.65—3.86 (2H, m), 4.24—4.36 (1H, m), 5.16 (2H, s), 5.50 (1H, m),
7.30—7.38 (5H, m).
The following compounds were prepared in a similar manner from 2b, c
and 3a, b.
(6b,8ab)-6-Amino-3,5,6,7,8,8a-hexahydro-5,5,8a-trimethyl-2(1H)-iso-
quinolinecarboxylic Acid Ethyl Ester (4b) 1H-NMR (CDCl3) d: 0.99
(3H, s), 1.13—2.04 (16H, complex m), 2.39—2.60 (2H, m), 3.82—3.84
(1H, m), 4.12—4.20 (2H, m), 4.25—4.35 (1H, m), 5.50 (1H, d).
(6a,8ab)-6-Amino-3,5,6,7,8,8a-hexahydro-5,5,8a-trimethyl-2(1H)-iso-
quinolinecarboxylic Acid Ethyl Ester (5b) 1H-NMR (CDCl3) d: 1.10
Experimental
Melting points were determined on a Büchi melting point apparatus and
were uncorrected. IR spectra were measured on a Perkin-Elmer 782 spec- (3H, s), 1.15—1.84 (14H, complex m), 2.58—2.68 (1H, m), 2.75 (1H, br),
trophotometer. 1H- and 13C-NMR spectra were obtained on a Bruker AC300 3.67—3.84 (2H, m), 4.12—4.34 (3H, m), 5.39—5.44 (1H, m).
spectrometer using tetramethylsilane as internal standard. MS spectra were
measured with a Nermag Model R30-10 spectrometer. Structural assign- 6-isoquinolineamine (6) A solution of 2c (3.27 g, 8.37 mmol) in methanol
(6b,8ab)-N-Trifluoroacetyl-1,2,3,5,6,7,8,8a-octahydro-5,5,8a-trimethyl-
ments for all new compounds are consistent with their spectra. Elemental (30 ml) and 3 N HCl (4.2 ml) was refluxed for 6 h. After cooling, the solution
analyses were performed on a Perkin-Elmer 240C apparatus.
(6b,8ab)-3,5,6,7,8,8a-Hexahydro-5,5,8a-trimethyl-6-trifluoroacetyl-
was evaporated, the resulting residue was poured into ice-cold 1 N NaOH
(15 ml) and extracted with EtOAc. The combined organic layer was washed
amino-2(1H)-isoquinolinecarboxylic Acid Phenylmethyl Ester (2a) and with brine, dried over MgSO4 and evaporated to afford 6 as a white solid
(6a,8ab)-3,5,6,7,8,8a-Hexahydro-5,5,8a-trimethyl-6-trifluoroacetyl-
(2.1 g, 87.5%): mp 160 °C. 1H-NMR (CDCl3) d: 1.08 (3H, s, CH3), 1.09
amino-2(1H)-isoquinolinecarboxylic Acid Phenylmethyl Ester (3a) To (3H, s, CH3), 1.22—1.34 (4H, m, CH3, H-8a), 1.46—1.53 (1H, m, H-8b),
a solution of 1a (65 g, 20 mmol) in 700 ml of methanol was added ammo- 1.63 (1H, br s, NH), 1.70—1.86 (2H, m, H-7), 2.48 (1H, d, Jϭ12.2 Hz, H-
nium acetate (153 g, 2 mol), the pH of the resulting solution was adjusted at 1a), 2.87 (1H, d, Jϭ12.1 Hz, H1b), 3.36 (1H, dd, Jϭ3.8, 18 Hz, H-3a), 3.45
7.3 with AcOH then NaBH3CN (20 g, 30 mmol) was added portionwise. The (1H, dd, Jϭ2.4, 18.0 Hz, H-3b), 3.74—3.82 (1H, m, 6a-H), 5.59 (1H, t,
mixture was stirred for 2 d at room temperature then concentrated. The Jϭ3.8 Hz, H-4), 6.13 (1H, br d, CF3CONH). This solid was converted into
residue was extracted with EtOAc, washed with water, dried (MgSO4) its tosylate: mp Ͼ260 °C. Anal. Calcd for C14H21F3N2O·C7H8O3S: C, 53.73;
and evaporated to afford 3,5,6,7,8,8a-hexahydro-5,5,8a-trimethyl-6-amino- H, 6.39; N, 5.97. Found: C, 53.73; H, 6.28; N, 5.93.
2(1H)-isoquinolinecarboxylic acid phenylmethyl ester (52 g, 82%) as an oil.
To a solution of this product (50 g, 0.15 mol) and Et3N (25.5 ml) in 200 ml of
(6b,8ab)-N-Trifluoroacetyl-1,2,3,5,6,7,8,8a-octahydro-2-dodecyl-
5,5,8a-trimethyl-6-isoquinolineamine (7) Method B A suspension of 6
THF was added dropwise TFAA (25.8 ml, 0.18 mol) in 50 ml of THF keep- (2.38 g, 8.2 mmol), K2CO3 (2.37 g, 16.4 mmol) and of 1-bromododecane
ing the temperature at 0 °C then the mixture was stirred overnight at room
(2.25 g, 9.03 mmol) in 50 ml of acetonitrile was refluxed for 8 h. After cool-
temperature. After evaporation, the residue was dissolved in ether, washed ing, the mixture was poured into brine and extracted with EtOAc. The com-
with 1 N HCl, with water, dried (MgSO4) and evaporated. Purification of the
bined organic layer was washed with water, dried (MgSO4) and concentrated
oily residue by silica-gel column chromatography (isopropyl ether–methyl- in vacuo. The oily residue was separated on a silica gel column eluting with
cyclohexane, 9/1) gave 2a (37.1 g, 59%) as a solid: mp 138 °C and 3a (6.5 g, a solvent mixture of hexane–EtOAc (9/1) to afford 7 as a solid (3.2 g, 85%):
1
1
12%) as an oil: nD36ϭ1.5145. 2a: H-NMR (CDCl3) d: 1.07—1.09 (6H, br s,
mp 80 °C. H-NMR (CDCl3) d: 0.89 (3H, t, Jϭ6.46 Hz), 1.07 (3H, s), 1.09
CH3), 1.16 (1.5H, s, CH3), 1.20 (1.5H, s, CH3), 1.28—1.39 (1H, m, H-8a), (3H, s), 1.28—1.34 (23H, m), 1.45—1.51 (2H, m), 1.68—1.87 (3H, m),
1.53—1.64 (1H, m, H-8b), 1.71—1.85 (2H, m, H-7a, H-7b), 2.56 (0.5H, d, 2.21—2.39 (2H, m), 2.46 (1H, d, Jϭ11.3 Hz), 2.65 (1H, dd, Jϭ2.09,
Jϭ12.5 Hz, H-1a), 2.62 (0.5H, d, Jϭ12.7 Hz, H-1a), 3.67—3.91 (3H, m, H- 16.7 Hz), 3.30 (1H, dd, Jϭ3.96, 16.7 Hz), 3.71—3.80 (1H, m), 5.55 (1H, dd,
3a, H-1b, H-6a), 4.25—4.38 (1H, m, H-3b), 5.16 (2H, s, CH2–Ph), 5.55 (1H,
d, Jϭ21.9 Hz, H-4), 6.19 (1H, d, Jϭ9.4 Hz, CF3CONH), 7.30—7.38 (5H, m,
Jϭ2.4, 4 Hz), 6.11 (1H, br d).
(6b,8ab)-N-Methyl-1,2,3,5,6,7,8,8a-octahydro-2-dodecyl-5,5,8a-
Ph). Anal. Calcd for C22H27F31N2O3: C, 62.25; H, 6.41; N, 6.60. Found: C, trimethyl-6-isoquinolineamine (8d) A solution of 7 (3.5 g , 11 mmol) in
62.17; H, 6.39; N, 6.54. 3a: H-NMR (250 MHz, CDCl3) d: 1.08 (3H, s, 20 ml of DMF was carefully added to a suspension of NaH (0.43 g, 60% dis-
CH3), 1.22—1.27 (7H, m, CH3, H-8a), 1.43—1.54 (1H, m, H-8b), 1.70—
persion in mineral oil). After completion of the addition, the mixture was
1.81 (1H, m, H-7a), 2.09—2.27 (1H, m, H-7b), 2.54—2.65 (1H, m, H-1a), heated at 40 °C for 1 h. The mixture was cooled, iodomethane (0.8 ml,
3.73—4.03 (3H, m, H-3a, H-1a, H-6b), 4.28—4.41 (1H, m, H-3b), 5.17 (2H,
13 mmol) was then added and the reaction mixture was stirred at room tem-
s, CH2–Ph), 5.49—5.56 (1H, m, H-4), 6.00 (1H, d, Jϭ7.5 Hz, CF3CONH), perature for 48 h. The mixture was poured into water and extracted with
7.31—7.38 (5H, m, Ph).
ether. The organic phase was washed with water, dried (MgSO4) and evapo-
The following compounds were prepared in a similar manner from 1b and rated to give (6b,8ab)-N-methyl-N-trifluoroacetyl-1,2,3,5,6,7,8,8a-octahy-
1c.
dro-2-dodecyl-5,5,8a-trimethyl-6-isoquinolineamine as a solid (2.6 g, 72%):
mp 60 °C. 2.5 g (5 mmol) of the previous compound was refluxed for 48 h in
200 ml of methanol, 50 ml of water and K2CO3 (14.6 g, 0.1 mol). After cool-
ing, the reaction mixture was evaporated. The residue was partitioned be-
tween water and methylene chloride. The organic phase was washed with
water, dried (MgSO4) and concentrated in vacuo. The residue was purified
by chromatography with CH2Cl2–CH3OH–NH4OH (98.5/1/0.5) as eluent to
give 8d as an oil (1.5 g, 79%). 1H-NMR (CDCl3) d: 0.88 (3H, t, Jϭ6.42 Hz),
(6b,8ab)-3,5,6,7,8,8a-Hexahydro-5,5,8a-trimethyl-6-trifluoroacetyl-
amino-2(1H)isoquinolinecarboxylic Acid Ethyl Ester (2b) mp 70—
80 °C. H-NMR (CDCl3) d: 1.08 (3H, s), 1.10 (3H, s), 1.18 (1.5H, s), 1.19
(1.5H, s), 1.27 (3H, t, Jϭ5.08 Hz), 1.37 (1H, m), 1.55 (1H, m), 1.80 (2H,
m), 2.56 (1H, m), 3.76 (3H, m), 4.17 (2H, q, Jϭ5.08 Hz), 4.32 (1H, m), 5.55
(1H, m), 6.13 (1H, d, Jϭ9.5 Hz).
1
(6a,8ab)-3,5,6,7,8,8a-Hexahydro-5,5,8a-trimethyl-6-trifluoroacetyl-
amino-2(1H)-isoquinolinecarboxylic Acid Ethyl Ester (3b) nD32ϭ 0.94 (3H, s), 1.00 (3H, s), 1.13 (3H, s), 1.25 (24H, complex m), 1.42—1.56

324
Vol. 50, No. 3
(1H, m), 1.74—1.96 (2H, m), 2.19—2.45 (6H, m), 2.59—2.85 (1H, dd, was adjusted to 7 by addition of AcOH, NaBH3CN (0.82 g, 13.0 mmol) was
Jϭ2.11, 16.3 Hz), 3.25—3.32 (1H, dd, Jϭ4.28, 16.3 Hz), 5.47—5.49 (1H, then carefully added. The resulting solution was stirred overnight. After
m). This oil was converted into its oxalate: mp 134 °C. Anal. Calcd for evaporation, the residue was poured into ice-cooled dilute NaOH and ex-
C25H48N2·C2H2O4: C, 65.72; H, 10.04; N, 5.47. Found: C, 65.38; H, 9.79; N, tracted with EtOAc. The organic layer was washed with brine, dried
5.49.
(MgSO4) evaporated and purified by silica gel column chromatography
(6b,8ab)-1,2,3,5,6,7,8,8a-Octahydro-2-dodecyl-5,5,8a-trimethyl-6-iso- (toluene, iso-PrOH 98/2) to give 8c (3.25 g, 74%) as a solid. This solid was
quinolineamine (8a) Following Method A the title compound was pre- converted into its fumarate salt: mp 193 °C. 1H-NMR (CD3OD) d: 0.89 (3H,
1
pared from 7 as an oil. H-NMR (CDCl3) d: 0.88 (3H, t, Jϭ6.46 Hz), 1.00 t, Jϭ6.5 Hz), 1.29 (20H, m), 1.39 (6H, s), 1.48 (3H, s), 1.80 (2H, m), 2.08
(3H, s), 1.10 (3H, s), 1.16—1.71 (29H, m), 1.77 (1H, d, Jϭ10.6 Hz), 2.19— (1H, m), 2.20 (1H, m), 2.78 (1H, d, Jϭ11.8 Hz), 2.89 (6H, s), 3.10 (3H, m),
2.45 (4H, m), 2.62 (1H, dd, Jϭ2.15, 16.4 Hz), 3.29 (1H, dd, Jϭ3.52, 3.27 (1H, d, Jϭ11.8 Hz), 3.59 (1H, dd, Jϭ16.9, 2.0 Hz), 3.90 (1H, dd,
16.40 Hz), 5.48 (1H, dd, Jϭ2.19, 4.43 Hz). This oil was converted into
Jϭ16.9, 3.5 Hz), 5.75 (1H, t, Jϭ2.4 Hz), 6.73 (6H, s). Anal. Calcd for
its fumarate (1.25 g, 75%): mp 170—173 °C. Anal. Calcd for C26H50N2·3C4H4O4: C, 61.76; H, 8.46; N, 3.79. Found: C, 61.87; H, 8.54; N,
C24H46N2·C4H4O4: C, 74.23; H, 11.50; N, 6.66. Found: C, 74.24; H, 11.61; 3.41.
N, 6.54.
(6b,8ab)-3,5,6,7,8,8a-Hexahydro-6-dimethylamino-5,5,8a-trimethyl-
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-[-1-[2-methyl-3-
[4-isopropylphenyl]-propyl]-5,5,8a-trimethyl-6-isoquinolineamine (8e)
2(1H)-isoquinolinecarboxylic Acid Phenylmethyl Ester (9a). Method C This compound was prepared using Method D starting from 11 (3 g,
To a solution of 4a (27 g, 80 mmol) in 500 ml of acetonitrile were added 13.5 mmol), 3-[4-isopropyl phenyl)]-2-methyl propanal (2.8 g, 14.7 mmol),
74 ml of formaldehyde (37% solution in water). The pH of the resulting
mixture was adjusted to 7.5 by addition of acetic acid. NaBH3CN (15.5 g,
NaBH3CN (1.28 g, 20.3 mmol), Na2SO4 (2 g, 13.5 mmol) in CH3OH
(100 ml) as an oil in a 41% yield (2.2 g). This oil was converted into its fu-
0.25 mol) was added portionwise, then the reaction mixture was stirred at marate: mp 142 °C. 1H-NMR (CD3OD) d: 0.84 (3H, d, Jϭ6.6 Hz), 1.22 (6H,
room temperature for 12 h and evaporated. The residue was taken up with d, Jϭ6.9 Hz), 1.26 (3H, s), 1.34 (3H, s), 1.40 (2H, m), 1.43 (3H, s), 1.70
1 N NaOH and extracted with EtOAc. The organic layers were washed with (1H, m), 1.99 (3H, m), 2.23 (4H, m), 2.63 (1H, d, Jϭ10.8 Hz), 2.68 (1H, dd,
water, dried (MgSO4) and concentrated. Purification of the residue with Jϭ18.4, 2.1 Hz), 2.84 (2H, m), 2.86 (6H, s), 3.0 (1H, dd, Jϭ12.6, 3.4 Hz),
chromatography (eluent CH2Cl2–CH3OH–NH4OH, 8.5/1/0.5) gave 9a
(23.5 g, 80%) as an oil. H-NMR (CDCl3) d: 1.02 (3H, s), 1.07—1.25 (8H,
m), 1.54—1.73 (4H, m), 1.96—2.02 (1H, m), 2.29 (6H, s), 2.46—2.59 (1H,
m), 3.62—3.84 (2H, m), 4.20—4.36 (1H, m), 5.16 (2H, s), 5.40—5.48 (1H,
s), 7.32—7.35 (5H, m).
5.67 (1H, dd, Jϭ4.1, 2.4 Hz), 6.67 (2H, s), 7.09 (4H, m). 13C-NMR
(CD3OD) d: 18.1, 18.5, 24.5, 24.7, 26.5, 27.5, 33.8, 34.9, 36.5, 37.5, 41.4,
41.7, 43.9, 55.7, 65.4, 67.9, 76.3, 121.3, 127.1, 130.2, 138.3, 139.3, 147.3,
147.5, 171.8. Anal. Calcd for C27H44N2·C4H4O4: C, 72.62; H, 9.44; N, 5.46.
Found: C, 72.73; H, 9.28; N, 5.41.
1
(6a,8ab)-3,5,6,7,8,8a-Hexahydro-6-dimethylamino-5,5,8a-trimethyl-
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-(6,6-dimethyl-2-
2(1H)-isoquinolinecarboxylic Acid Ethyl Ester (10b) The titled com- hepten-4-yn-1-yl)-5,5,8a-trimethyl-6-isoquinolineamine (8f) The titled
pound was prepared using the same procedure as described above, starting compound was prepared starting from 11 (3.5 g, 15.8 mmol), 1-bromo-6,6-
from 5b (1.2 g, 4.5 mmol) in 60% yield as an oil (0.82 g). 1H-NMR (CDCl3) dimethyl-2-hepten-4-yne (3.8 g, 18.8 mmol) and K2CO3 in CH3CN to afford
d: 1.15—1.20 (9H, m), 1.26 (3H, t, Jϭ6.74 Hz), 1.38—1.47 (2H, m), 1.78—
1.88 (2H, m), 2.30 (6H, s), 2.43 (1H, t, Jϭ4.45 Hz), 2.53—2.63 (1H, m), (1H, m), 1.14 (1.95H, s), 1.15 (1.05H, s), 1.25 (9H, s), 1.27 (1.05H, s), 1.28
8f (1.4 g, 26%) as an oil (E/Z 65/35). 1H-NMR (CDCl3) d: 1.05 (3H, s), 1.10
3.64—3.81 (2H, m), 4.12—4.26 (3H, m), 5.44 (1H, br d).
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-5,5,8a-trimethyl-6-
isoquinolineamine (11) A mixture of 9a (21.5 g, 60 mmol) and 3.5 g of
(1.95H, s), 1.51 (1H, m), 1.60—1.85 (3H, m), 1.95 (1H, m), 2.29 (6H, s),
2.43 (1H, m), 2.65 (0.65H, dd, Jϭ10.3, 2.1 Hz), 2.75 (0.35H, dd, Jϭ10.5,
2.2 Hz), 2.88 (0.65H, dd, Jϭ14.0, 7.0 Hz), 3.08 (0.65H, dd, Jϭ12.5, 5.8 Hz),
5% Pd/C in 250 ml of acetic acid was stirred at room temperature under 3.25 (1.7H, m), 5.45 (1H, m), 5.62 (1H, m), 5.92 (0.35H, m), 6.04 (0.65H,
1 atm of H2. The catalyst was filtered and the solvent was removed. The m). Anal. Calcd for C23H38N2: C, 80.64; H, 11.18; N, 8.18. Found: C, 80.35;
residue was taken up with 1 N NaOH and extracted with ether. The organic H, 10.86; N, 8.00.
solution was washed with water, dried over MgSO4 and concentrated to give
11 (12.6 g, 95%) as a solid: mp 92 °C. H-NMR (CDCl3) d: 1.04 (3H, s,
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-(3-phenyl-2-
propen-1-yl)-5,5,8a-trimethyl-6-isoquinolineamine (8g). Method E
1
CH3), 1.08—1.22 (4H, m, H-8a CH3), 1.48 (3H, s, CH3), 1.49—1.54 (1H, m, 1,1Ј-Carbonyldiimidazole (2.6 g, 16 mmol) was added portionwise to a solu-
H-8b), 1.63—1.73 (3H, m, H-7, NH), 1.96—2.01 (1H, s, H-6a), 2.29 (6H, s, tion of trans-cinnamic acid (2.4 g, 16 mmol) in 50 ml of THF and the reac-
N(CH3)2), 2.43 (1H, d, Jϭ12.2 Hz, H-1a), 2.60 (1H, d, Jϭ12.2 Hz, H-1a), tion mixture was stirred at room temperature for 0.5 h then heated at 50 °C
3.31 (1H, dd, Jϭ17.8, 3.74 Hz, H-3a), 3.41 (1H, dd, Jϭ17.7, 2.39 Hz, H-3b), for 1 h. After cooling at 5 °C, a solution of 11 (3 g, 13.5 mmol) in 40 ml of
5.48 (1H, m, H-4).
(6a,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-5,5,8a-trimethyl-6-
THF was added dropwise. The reaction mixture was stirred overnight, di-
luted with water then extracted with ether. The organic phase was washed
isoquinolineamine (12) Trimethylsilyl chloride (4 ml) were carefully with water, dried (MgSO4) and concentrated to leave an oil which was puri-
added at room temperature to a solution of 10b (0.8 g, 2.7 mmol) and NaI fied by chromatography on silica gel eluting with a mixture of CH2Cl2–
(5.2 g, 34 mmol) in 15 ml of acetonitrile. The resulting mixture was refluxed CH3OH–NH4OH (9/0.9/0.1) to afford (6b,8ab)-N,N-dimethyl-1,2,3,5,6,7,
for 24 h. After cooling the solvent was removed under reduced pressure and 8,8a-octahydro-2-(3-phenyl-2-propenoyl)-5,5,8a-trimethyl-6-isoquinoline-
the residue was taken up with 1 N HCl, then washed with ether. The aqueous
amine (2.76 g, 59%). This material (1.5 g, 4.26 mmol) was dissolved in
phase was made basic with 1 N NaOH and extracted with ether. The ethereal 30 ml of toluene and a 70% solution of Red-Al in toluene (2.5 ml, 8.6 mmol)
phase was washed with water, dried over MgSO4 and the solvent was re- was added dropwise. The reaction mixture was stirred at room temperature
moved under reduced pressure to provide 12 as a crude solid (0.5 g, 77%):
for 2.5 h then cooled to 0 °C. A solution (50 ml) of 5 N NaOH was carefully
mp 103 °C. 1H-NMR (CDCl3) d: 1.15 (3H, s, CH3), 1.17 (3H, s, CH3), added and the resulting mixture was allowed to warm to room temperature
1.22—1.49 (5H, m, CH3, H-8), 1.70 (1H, s, NH), 1.78—1.88 (2H, m, H-7), with stirring for 0.5 h. Ether was then added and the mixture was washed
2.32 (6H, s, N(CH3)2), 2.41 (1H, m, H-6b), 2.49 (1H, d, Jϭ12.2 Hz, H-1a), with water, dried then concentrated to dryness to give 8g (1.4 g, 100%) as a
1
2.60 (1H, d, Jϭ12.2 Hz, H-1b), 3.36 (1H, dd, Jϭ17.8, 4.15 Hz, H-3a), 3.45
(1H, dd, Jϭ17.9, 2.55 Hz, H-3b), 5.46 (1H, m, H-4).
pale-yellow oil. This oil was converted to a tosylate: mp 210 °C. H-NMR
(DMSO-d6) d: 1.14 (3H, s), 1.25 (1H, m), 1.29 (3H, s), 1.38 (3H, s), 1.75
(6a,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-dodecyl-5,5,8a- (1H, d, Jϭ13.1 Hz), 2.05 (2H, m), 2.28 (6H, s), 2.76 (4H, m), 2.87 (3H, m),
trimethyl-6-isoquinolineamine (8b) The title compound was prepared 2.99 (1H, t, Jϭ7.3 Hz), 3.32 (1H, d, Jϭ12.1 Hz), 3.67 (1H, m), 3.82 (1H,
following Method B starting from 12 (0.42 g, 1.89 mmol), n-bromododecane m), 4.0 (2H, m), 5.66 (1H, s), 6.38 (1H, dt, Jϭ15.8, 7.1 Hz), 6.85 (1H, d,
(0.5 g, 2 mmol) and K2CO3 in CH3CN to afford 8b (37%) as an oil which
Jϭ15.8 Hz), 7.12 (4H, d, Jϭ7.9 Hz), 7.35 (3H, m), 7.47 (6H, m), 8.45 (1H,
was converted into its oxalate: mp 139 °C. 1H-NMR (DMSO-d6) d: 0.85 br s), 9.19 (1H, br s). 13C-NMR (DMSO-d6) d: 16.3, 20.7, 23.4, 24.6, 25.5,
(3H, t, Jϭ6.4 Hz), 1.21 (3H, s), 1.25 (21H, m), 1.35 (3H, s), 1.47 (4H, m), 32.7, 33.7, 34.5, 46.1, 50.3, 57.8, 61.3, 73.0, 115.1, 117.3, 125.4, 126.8,
2.0 (1H, m), 2.68 (6H, s), 2.73 (3H, m), 2.91 (1H, d, Jϭ11.0 Hz), 3.19 (2H, 128.0, 128.7, 135.2, 137.7, 139.0, 145.3, 146.2. Anal. Calcd for
m), 3.84 (1H, dd, Jϭ17.6, 3.5 Hz), 5.52 (1H, br s), 6.9 (4H, br s). Anal. C23H34N2·2C7H8O3S: C, 64.10; H, 7.23; N, 3.86. Found: C, 63.92; H, 7.22;
Calcd for C26H50N2·2C4H4O4: C, 63.13; H, 9.54; N, 4.91. Found: C, 62.81; N, 4.05.
H, 9.50; N, 5.09.
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-(3,3-diphenyl-2-
propen-1-yl)-5,5,8a-trimethyl-6-isoquinolineamine (8h) The title com-
(6b,8ab)-N,N-Dimethyl-1,2,3,5,6,7,8,8a-octahydro-2-dodecyl-5,5,8a-
trimethyl-6-isoquinolineamine (8c). Method D The pH of a solution of pound was prepared following Method E starting from 11 (3 g, 13.5 mmol),
11 (2.3 g, 10.3 mmol) and dodecanal (2.3 g, 12.5 mmol) in 60 ml of methanol 3-phenyl-2-propenoic acid (3.6 g, 16 mmol) and carbonyl diimidazole (2.6 g,

March 2002
325
16 mmol) in THF (50 ml) to afford the corresponding amide. This was re- Calcd for C21H41NO2·HCl: C, 67.07; H, 11.26; N, 3.73. Found: C, 67.02; H,
duced with RedAl (7 ml, 24 mmol) to give 8h (5.1 g, 95%) which was con-
verted into its oxalate: mp 150 °C. H-NMR (DMSO-d6) d: 1.14 (3H, s),
11.32; N, 3.85.
1
a,a-Dimethyl-1-dodecyl-4-piperidineacetamide (19a). Method F The
1.17 (1H, m), 1.26 (3H, s), 1.34 (3H, s), 1.60 (1H, d, Jϭ13.0 Hz), 2.01 (3H, compound 18 (17.9 g, 0.048 mol) was added portionwise to SOCl2 (100 ml,
m), 2.6—2.9 (9H, m), 3.28 (2H, m), 3.50 (1H, dd, Jϭ16.8, 3.7 Hz), 5.56 1.37 mol), the mixture was then refluxed for 7.5 h. The solution was evapo-
(1H, s), 6.21 (1H, t, Jϭ6.7 Hz), 7.19 (4H, m), 7.39 (6H, m). Anal. Calcd for rated in vacuo to afford a,a-dimethyl-1-dodecyl-4-piperidineacetyl chloride
C29H38N2·2C2H2O4: C, 64.31; H, 7.26; N, 4.54. Found: C, 64.62; H, 6.93; N, hydrochloride which was used in the following reactions without purifica-
4.56.
4-Hydroxy-a,a-dimethyl-1-phenylmethyl-4-piperidineacetic Acid
tion.
Liquid ammonia (80 ml) at Ϫ5 °C was carefully added to a solution of the
Ethyl Ester (14) A solution of diisopropylamine (152.8 ml, 1.09 mol) in product obtained in the previous step (8.6 g, 0.022 mol) in a 2/1 mixture of
dry THF (100 ml) was stirred at Ϫ50 °C under an atmosphere of N2 and a toluene–CH2Cl2 (100 ml). After stirring for 72 h at room temperature, the re-
2.5 M solution of nBuLi in hexane (400 ml, 1 mol) was added dropwise. The
action mixture was poured in water then extracted with EtOAc. The organic
mixture was stirred at Ϫ50 °C for 45 min, then 2-methylpropanoic acid ethyl extracts were washed with water, dried over MgSO4 and concentrated in
ester (121.8 ml, 0.91 mol) in THF (100 ml) was added dropwise and stirring vacuo. Purification of the residue by flash chromatography (EtOAc–
was maintained during 1 h. A solution of 1-phenylmethyl-4-piperidone 13 CH3OH–NH4OH, 9/1/0.5) provided 19a (5.2 g, 69%) as a colorless powder:
1
(120.5 ml, 0.68 mol) in THF (100 ml) was added dropwise at Ϫ50 °C, then mp 123 °C (isopropyl ether). IR (KBr) 1630, 1650, 3220, 3400 cmϪ1; H-
the reaction mixture was warmed to room temperature overnight. Saturated NMR (CDCl3) d: 0.88 (3H, t, Jϭ6.4 Hz), 1.13 (6H, s), 1.25—1.60 (25H, m),
aqueous NH4Cl (400 ml) was added, and the resulting mixture was then ex- 1.87 (2H, t, Jϭ11.2 Hz), 2.27 (2H, m), 2.99 (2H, m), 5.47 (1H, br s), 5.63
tracted with ether. The organic layer was washed with brine, dried over (1H, br s). Anal. Calcd for C21H42N2O: C, 74.49; H, 12.51; N, 8.28. Found:
MgSO4 and concentrated in vacuo to leave an oil which was distilled under C, 74.25; H, 12.55; N, 8.25.
reduced pressure to afforded 14 (172.3 g, 83%) as an orange oil: bp 150—
The following compounds were prepared according to Method F.
1-Dodecyl-N,a,a-trimethyl-4-piperidineacetamide (19b) The title
1
156 °C/0.45 mmHg. IR (neat): 3500, 1700 cmϪ1; H-NMR (CDCl3) d: 1.23
(6H, s), 1.27 (3H, t, Jϭ7.1 Hz), 1.43 (2H, m), 1.78 (2H, dt, Jϭ4.39, compound was prepared from a,a-dimethyl-1-dodecyl-4-piperidineacetyl
12.9 Hz), 2.37 (2H, dt, Jϭ2.39, 12.99 Hz), 2.69 (2H, m), 3.48 (1H, s), 3.52 chloride hydrochloride (25 g, 63 mmol) and methaneamine (300 ml) in
(2H, s), 4.16 (2H, q, Jϭ7.1 Hz), 7.22—7.33 (5H, m). Anal. Calcd for CHCl3 (200 ml) to afford 19b (16 g, 72%) as a solid: mp 78 °C. H-NMR
1
C18H27NO3: C, 70.79; H, 8.91; N, 4.59. Found: C, 70.43; H, 8.81; N, 4.96.
1,2,3,6-Tetrahydro-a,a-dimethyl-1-phenylmethyl-4-pyridineacetic m), 1.87—1.94 (2H, m), 2.27—2.32 (2H, m), 2.80 (3H, d), 2.98—3.02 (2H,
Acid Ethyl Ester Hydrochloride (15) To a stirred solution of 14 (50 g, m), 5.66—5.67 (1H, m).
(CDCl3) d: 0.87 (3H, t), 1.10 (6H, s), 1.25—1.54 (24H, m), 1.62—1.70 (1H,
0.164 mol) in CHCl3 (200 ml) and DMF (0.52 ml) was added SOCl2 (24 ml,
1-Dodecyl-N-ethyl-a,a-dimethyl-4-piperidineacetamide (19c) This
0.33 mol) dropwise. The reaction mixture was stirred under reflux for 8 h, was obtained from a,a-dimethyl-1-dodecyl-4-piperidineacetyl chloride hy-
then the solution was evaporated in vacuo. The resulting residue was alka- drochloride (6 g, 15 mmol) and ethaneamine (500 ml) in CHCl3 (50 ml) in
lined with 10 N NaOH (20 ml) and extracted with ether. The combined ex- 54% yield: mp 67 °C. 1H-NMR (CDCl3) d: 0.87 (3H, t, Jϭ6.33 Hz), 1.10—
tracts were washed with brine, dried over MgSO4 and concentrated in vacuo. 1.15 (9H, m), 1.25—1.58 (24H, m), 1.65—1.69 (1H, m), 1.95 (2H, m), 2.34
Hydrochloride salt was prepared in iso-PrOH solution by adding HCl gas to (2H, m), 3.02—3.06 (2H, m), 3.26—3.31 (2H, m), 5.82 (1H, m).
afford 15 as a white powder, which was recrystallized from iso-PrOH
(38.9 g, 74%): mp 208 °C. H-NMR (DMSO-d6) d: 1.16 (3H, t, Jϭ7.1 Hz), Using propaneamine (21 ml, 0.25 mol) and a,a-dimethyl-1-dodecyl-4-
1.24 (6H, s), 2.17 (2H, m), 3.02—3.57 (4H, complex m), 4.05 (2H, q,
1-Dodecyl-N-propyl-a,a-dimethyl-4-piperidineacetamide (19d)
1
piperidineacetyl chloride hydrochloride (10 g, 25 mmol) in CHCl3 (100 ml),
1
Jϭ7.1 Hz), 4.27 (2H, m), 5.54 (1H, m), 7.44 (3H, m), 7.58 (2H, m), 10.90
19d was obtained (7.5 g, 79%) as a solid: mp 72—75 °C. H-NMR (CDCl3)
1
(1H, br s). H-NMR (DMSO-d6ϩD2O) d: 1.10 (3H, t, Jϭ7.1 Hz), 1.19 (6H,
d: 0.85—0.94 (6H, m), 1.10 (6H, s), 1.25 (19H, m), 1.42—1.57 (7H, m),
s), 2.21 (2H, m), 3.14 (2H, m), 3.50 (2H, m), 4.00 (2H, q, Jϭ7.1 Hz), 4.17 1.63—1.67 (1H, m), 1.92 (2H, m), 2.31 (2H, m), 3.00—3.03 (2H, m),
(2H, s), 5.50 (1H, m), 7.42 (5H, s). Anal. Calcd for C18H25NO2·HCl: C,
3.17—3.24 (2H, q, Jϭ6.92 Hz), 5.65 (1H, m).
66.76; H, 8.09; N, 4.32. Found: C, 66.89; H, 8.10; N, 4.36.
a,a-Dimethyl-4-piperidineacetic Acid Ethyl Ester (16) A solution of (19e) a,a-Dimethyl-1-dodecyl-4-piperidineacetyl chloride hydrochloride
15 (54.6 g, 0.169 mol) in CH3OH (800 ml) was hydrogenated over 5% Pd/C (10 g, 25 mmol) was reacted with isopropylamine (22 ml, 0.25 mol) in
(3 g) at 70 °C under 80 atm H2 pressure. After completion of the reaction, the CHCl3 (100 ml) to give 19e as a solid: mp 68 °C. H-NMR (CDCl3) d: 0.87
mixture was filtered, and the filtrate evaporated in vacuo. The solid residue (3H, t, Jϭ6.4 Hz), 1.08 (6H, s), 1.13 (6H, d), 1.25 (19H, m), 1.35—1.55
1-Dodecyl-N-(1-methylethyl)-a,a-dimethyl-4-piperidineacetamide
1
was quenched with 10 N NaOH, then extracted with CH2Cl2. The extracts
were washed with brine, dried over MgSO4 and evaporated in vacuo to give m), 4.04—4.11 (1H, m), 5.39—5.42 (1H, m).
16 as a yellow oil (28.6 g, 85%). IR (neat) 3150, 1730 cmϪ1 1H-NMR
1-Dodecyl-N-phenylmethyl-a,a-dimethyl-4-piperidineacetamide (19f)
(5H, m), 1.63—1.67 (1H, m), 1.93 (2H, m), 2.32 (2H, m), 3.01—3.03 (2H,
;
(CDCl3) d: 1.10 (6H, s), 1.25 (5H, m), 1.52 (3H, m), 1.69 (1H, m), 2.58 The title compound was obtained from a,a-dimethyl-1-dodecyl-4-
(2H, dt, Jϭ2.5, 12.2 Hz), 3.11 (2H, m), 4.12 (2H, q, Jϭ7.1 Hz). A sample of piperidineacetyl chloride hydrochloride (10 g, 25 mmol) and benzylamine
1
the free base was converted into its hydrochloride salt. mp: 190 °C (iso- (8.5 ml, 75 mmol) in CHCl3 (100 ml) as a solid (6.1 g, 57%): mp 74 °C. H-
PrOH). Anal. Calcd for C11H21NO2·HCl: C, 56.04; H, 9.41; N, 5.94. Found: NMR (CDCl3) d: 0.87 (3H, t, Jϭ6.4 Hz), 1.12 (6H, s), 1.25 (20H, m),
C, 56.44; H, 9.62; N, 5.96.
1.34—1.64 (4H, m), 1.62—1.71 (1H, m), 1.86 (2H, m), 2.27 (2H, m),
a,a-Dimethyl-1-dodecyl-4-piperidineacetic Acid Ethyl Ester (17) 2.95—2.99 (2H, m), 4.44 (2H, d, Jϭ5.39 Hz), 5.89 (1H, t, Jϭ5.39 Hz),
The title compound was obtained following Method B starting from 16
7.36—7.37 (5H, m).
(9.85 g, 0.05 mol), K2CO3 (17.3 g, 0.125 mol) and 1-bromododecane
1-Dodecyl-a,a-dimethyl-N,N-diethyl-4-piperidineacetamide (19j)
(14.9 ml, 0.062 mol) in CH3CN (50 ml). The crude compound was chro- The title compound was obtained from a,a-dimethyl-1-dodecyl-4-
matographed on SiO2 with hexane–EtOAc (9/1) as eluent to give 17 as an piperidineacetyl chloride hydrochloride (18 g, 45 mmol) and diethylamine
orange oil (6.7 g, 78%). IR (neat) 1730 cmϪ1; 1H-NMR (CDCl3) d: 0.88 (3H, (40 ml, 0.55 mol) in CHCl3 (300 ml) as a solid: mp Ͻ50 °C. 1H-NMR
t, Jϭ6.4 Hz), 1.11 (6H, s), 1.22—1.60 (28H, m), 1.85 (2H, dt, Jϭ2.0,
11.7 Hz), 2.27 (2H, m), 2.98 (2H, m), 4.12 (2H, q, Jϭ7.1 Hz). The free base 1.48—1.51 (4H, m), 1.64—1.67 (1H, m), 1.83—1.88 (2H, m), 2.27—2.32
was converted into its fumarate salt: mp 106 °C (EtOH–Et2O). Anal. Calcd (2H, m), 3.01—3.05 (2H, m), 3.39—3.41 (4H, br s).
(CDCl3) d: 0.87 (3H, t, Jϭ6.4 Hz), 1.13 (6H, s), 1.19 (6H, s), 1.25 (20H, m),
for C23H45NO2·C4H4O4: C, 67.04; H, 10.21; N, 2.90. Found: C, 66.70; H,
10.11; N, 2.96.
1-Dodecyl-N-phenylmethyl-N,a,a-trimethyl-4-piperidineacetamide
(19k) The title compound was obtained from a,a-dimethyl-1-dodecyl-4-
a,a-Dimethyl-1-dodecyl-4-piperidineacetic Acid Hydrochloride (18) piperidineacetyl chloride hydrochloride (30 g, 76 mmol) and N-methyl ben-
NaOH pellets (24.6 g, 0.614 mol) were added to a solution of 17 (22.5 g, zylamine (29.5 ml, 0.228 mol) in CHCl3 (300 ml) as an oil. 1H-NMR
0.061 mol) in 50% EtOH (210 ml), then the resulting mixture was refluxed (CDCl3) d: 0.87 (3H, t, Jϭ6.4 Hz), 1.24 (25H, br s), 1.51 (5H, m), 1.80 (3H,
while stirring for 3 d. The solution was poured while cooling into 5 N HCl
m), 2.28 (2H, m), 2.98 (5H, m), 4.84 (2H, s), 7.19—7.38 (5H, m). This com-
(200 ml), the resulting precipitate was filtrated and washed with ether. Re- pound was converted into its oxalate salt: mp 125 °C. Anal. Calcd for
crystallization from 80% EtOH gave 18 as a white solid. (17.8 g, 77%): mp C29H50N2O·C2H2O4: C, 69.88; H, 9.84; N, 5.26. Found: C, 69.52; H, 9.95;
192 °C. IR (KBr) 1700, 2650 cmϪ1
Jϭ6.4 Hz), 1.18 (6H, s), 1.27 (18H, m), 1.82 (5H, m), 2.12 (2H, m), 2.70
;
1H-NMR (CDCl3) d: 0.88 (3H, t,
N, 5.31.
b,b-Dimethyl-1-dodecyl-4-piperidineethanamine (20a). Method G
(2H, m), 2.94 (2H, m), 3.64 (2H, m), 9.25 (1H, br s), 11.50 (1H, br s). Anal. solution of Red-Al (70% in toluene, 10 ml, 34.3 mmol) was carefully added
A

326
Vol. 50, No. 3
to a solution of 19a (2.95 g, 8.7 mmol) in 80 ml of toluene. The resulting C24H48N2O·C7H8O3S: C, 67.34; H, 10.21; N, 5.07. Found: C, 67.18; H,
mixture was stirred for 1 h at room temperature, then heated to reflux for 3 h. 10.33; N, 4.78.
After cooling, 3 N NaOH (50 ml) was added dropwise and the mixture stirred
b,b-Dimethyl-N,N-dimethyl-4-pyridineethanamine (22i). Method H
for 24 h. The organic phase was washed with dilute NaOH, then with brine, To a solution of 4-isopropylpyridine (100 g, 0.82 mol), formaldehyde (37%
dried (MgSO4) and concentrated to dryness to afford a crude product which solution in water, 200 ml) in acetic acid (800 ml), dimethylamine (40% solu-
was purified by chromatography with EtOAc–CH3OH–NH4OH (98.5/1/0.5) tion in water, 300 ml) was added dropwise then the resulting solution was re-
as eluent to give 20a as an oil (1.8 g, 64%). This compound was converted fluxed for 3 d. Upon cooling, formaldehyde (100 ml) and dimethylamine
1
into its fumarate salt: mp 100—120 °C. H-NMR (CD3OD) d: 0.88 (3H, t, (150 ml) were again added and the reaction mixture was refluxed for 2 extra
Jϭ6.4 Hz), 0.99 (6H, s), 1.29—1.36 (20H, m), 1.57—1.71 (4H, m), 1.87—
days. The solvent was concentrated and 35% NaOH solution (400 ml) was
1.90 (2H, m), 2.95—3.00 (2H, m), 3.53—3.57 (2H, m), 6.63 (2H, s). Anal. carefully added upon cooling. The aqueous solution was washed with brine,
Calcd for C21H44N2·C4H4O4: C, 64.84; H, 10.98; N, 6.14. Found: C, 65.24; dried over MgSO4 and evaporated in vacuo to give an oil. This oil was puri-
H, 10.73; N, 5.92.
fied by vacuum distillation (bp 64—66 °C/0.3 mmHg) to give 22i (61.7 g,
42%). H-NMR (CDCl3) d: 1.31 (6H, s), 2.07 (6H, s), 2.45 (2H, s), 7.25—
7.30 (2H, m), 8.49—8.51 (2H, m).
1
The following compounds were prepared in a similar fashion.
1-Dodecyl-N,b,b-trimethyl-4-piperidineethanamine (20b) Yield:
79%. 1H-NMR (CDCl3) d: 0.85—0.90 (9H, m), 1.17—1.48 (24H, m),
1.57—1.62 (2H, m), 1.80—1.87 (2H, m), 2.24—2.29 (2H, m), 2.38 (2H, s),
1-[2-Methyl-2-(4-pyridinyl)propyl]piperidine (22l) The title com-
pound was prepared following Method H in a 17% yield as an oil. 1H-NMR
2.42 (3H, s), 2.97—3.01 (2H, m). Fumarate: mp 100—120 °C. Anal. Calcd (CDCl3) d: 1.27 (8H, s), 1.33—1.48 (4H, s), 2.16—2.21 (4H, m, CH2–N),
for C22H46N2·2C7H8O3S: C, 63.30; H, 9.15; N, 4.10. Found: C, 63.44; H,
9.35; N, 4.03.
2.35 (2H, s, N–CH2), 7.30—7.32 (2H, m), 8.47—8.49 (2H, m). The base
was converted into its fumarate: mp 177 °C. Anal. Calcd for C14H22N2·
C4H4O4: C, 61.21; H, 7.19; N, 7.14. Found: C, 61.29; H, 7.15; N, 7.23.
b,b-Dimethyl-N,N-dimethyl-4-piperidineethanamine (23i) In a Parr
1-Dodecyl-N-ethyl-b,b-dimethyl-4-piperidineethanamine (20c)
Yield: 100%. 1H-NMR (CDCl3) d: 0.76—0.89 (9H, m), 1.08 (3H, t,
Jϭ7.1 Hz), 1.21—1.47 (24H, m), 1.57—1.61 (2H, m), 1.79—1.88 (2H, m), apparatus, 22i (123 g, 0.69 mol) was dissolved in acetic acid (900 ml) and
2.23—2.29 (2H, m), 2.38 (2H, s), 2.62 (3H, q, Jϭ7.1 Hz), 2.96—3.01 (2H, PtO2 (12 g) was added. The reaction mixture then was stirred under a
m). Fumarate: mp 160 °C. Anal. Calcd for C23H48N2·2C4H4O4: C, 63.67; H, 1000 psi hydrogen pressure at 80 °C for 7 h and thereafter the catalyst was
9.65; N, 4.79. Found: C, 63.73; H, 9.56; N, 4.77.
filtered. The filtrate was evaporated in vacuo to give an oily residue which
1-Dodecyl-N-propyl-b,b-dimethyl-4-piperidineethanamine (20d)
was dissolved in water, basified under efficient cooling with 35% NaOH and
1
Yield: 95%. H-NMR (CDCl3) d: 0.84—0.92 (12H, m), 1.27—1.52 (26H, extracted with CHCl3. The organic extracts were washed with brine, dried
m), 1.57—1.6 (2H, m), 1.78—1.85 (2H, m), 2.23—2.28 (2H, m), 2.37 (2H,
(MgSO4) and concentrated to afford 23i as an oil (127 g, 100%) pure enough
s), 2.53 (3H, t, Jϭ7.2 Hz), 2.96—3.00 (2H, m). Fumarate: mp 186 °C. Anal. to be used in the next step.
Calcd for C24H50N2·C4H4O4: C, 64.18; H, 9.76; N, 4.68. Found: C, 64.51; H,
9.68; N, 4.55.
1-[2-Methyl-2-(4-piperidinyl)propyl]piperidine (23l) The compound
was prepared from 22l (10 g, 45.8 mmol) as described above in a quantitative
1-Dodecyl-N-(1-methylethyl)-b,b-dimethyl-4-piperidineethanamine yield and was used in next step without further purification.
(20e) Yield: 80%. 1H-NMR (CDCl3) d: 0.83 (9H, s), 0.88 (3H, t, Jϭ
N,N,b,b-Tetramethyl-1-dodecyl-4-piperidineethanamine (20i) The
6.2 Hz), 1.02 (6H, d, Jϭ6.2 Hz), 1.22—1.48 (21H, m), 1.57—1.61 (2H, m), title compound was prepared in a quantitative yield following the procedure
1.79—1.88 (2H, m), 2.24—2.29 (2H, m), 2.37 (2H, s), 2.63—2.71 (1H, m),
B starting from 23i (13 g, 70.5 mmol), n-bromododecane (19.7 g, 79 mmol),
2.97—3.01 (2H, m). Tosylate salt: mp 114 °C. Anal. Calcd for K2CO3 (24.4 g, 176 mmol) and NaI (0.5 g) in acetonitrile (150 ml). 1H-NMR
C24H50N2·2C7H8O3S: C, 64.18; H, 9.36; N, 3.94. Found: C, 63.88; H, 9.33; (CDCl3) d: 0.83 (6H, br s), 0.88 (3H, t, Jϭ6.45 Hz), 1.20—1.47 (23H, m),
N, 3.91.
1-Dodecyl-N-phenylmethyl-b,b-dimethyl-4-piperidineethanamine
1.59—1.63 (2H, m), 1.83 (2H, t, Jϭ11.4 Hz), 2.12 (2H, s), 2.23—2.28 (8H,
m), 2.96—3.00 (2H, m). It was converted to its fumarate: mp 132 °C. Anal.
(20f) Yield: 95%. 1H-NMR (CDCl3) d: 0.83 (6H, s), 0.88 (3H, t, (C23H48N2·2C4H4O4) C, H, N.
Jϭ6.4 Hz), 1.17—1.38 (22H, m), 1.47—1.55 (4H, m), 1.77—1.84 (2H, m),
4-[1,1-Dimethyl-2-(4-piperidinyl)ethyl]-1-dodecyl-piperidine (20l)
1
2.23—2.28 (2H, m), 2.38 (2H, s), 2.95—2.99 (2H, m), 3.77 (1H, s), 7.20—
The title compound was prepared following Method D in a 70% yield. H-
7.32 (5H, m). Fumarate: mp 174 °C. Anal. Calcd for C28H50N2·2C4H4O4: C, NMR (CDCl3) d: 0.78 (6H, s), 0.88 (3H, t, Jϭ6.4 Hz), 1.14—1.37 (22H, m),
66.84; H, 9.04; N, 4.33. Found: C, 66.65; H, 9.04; N, 4.26.
1.41—1.54 (7H, m), 1.59—1.64 (2H, m), 1.79—1.87 (2H, m), 2.06 (2H, s),
1-Dodecyl-N,N-diethyl-b,b-dimethyl-4-piperidineethanamine (20j)
2.25—2.31 (2H, m), 2.39 (4H, t, Jϭ4.8 Hz), 2.98—3.02 (2H, m). The base
Yield: 85%. 1H-NMR (CDCl3) d: 0.77 (6H, s), 0.85 (3H, t, Jϭ6.4 Hz), 0.92 was converted into its maleate: mp 129 °C. Anal. (C26H52N2·2C4H4O4) C, H,
(6H, t, Jϭ7.0 Hz), 1.13—1.46 (23H, m), 1.59—1.63 (2H, m), 1.80—1.83 N.
(2H, m), 2.16 (2H, s), 2.25—2.30 (2H, m), 2.48 (2H, q, Jϭ7.0 Hz), 2.98—
3.02 (2H, m). As fumarate salt: mp 108 °C. Anal. Calcd for C25H52N2· pound was prepared in a quantitative yield following procedure B from 23i
b,b,N,N,1-Pentamethyl-4-piperidineethanamine (20m) The title com-
2C4H4O4: C, 63.96; H, 9.88; N, 4.52. Found: C, 63.66; H, 10.04; N, 4.52.
(1.3 g, 7.05 mmol), iodomethane (1.13 g, 8 mmol) and K2CO3 (2.5 g,
1.8 mmol) in acetonitrile (20 ml). H-NMR (CDCl3) d: 0.83 (6H, s), 1.19—
1
1-Dodecyl-N-phenylmethyl-N,b,b-trimethyl-4-piperidineethanamine
(20k) Yield: 82%. 1H-NMR (CDCl3) d: 0.86—0.90 (9H, s), 1.25—1.47 1.30 (3H, m), 1.60—1.64 (2H, m), 1.82—1.90 (2H, m), 2.12 (2H, s), 2.24
(23H, m), 1.59—1.64 (2H, m), 1.77—1.84 (2H, m), 2.18 (3H, s), 2.23— (3H, s), 2.28 (6H, s), 2.87—2.91 (2H, m). This was converted into its fu-
2.35 (4H, m), 2.98—2.99 (2H, m), 3.54 (2H, s), 7.20—7.38 (5H, m). Fu-
marate: mp 124 °C. Anal. Calcd for C29H52N2·C4H4O4: C, 72.75; H, 10.36;
N, 5.14. Found: C, 72.69; H, 10.45; N, 5.07.
marate: mp 160 °C. Anal. (C12H26N2·2C4H4O4) C, H, N.
2-[3-[4-[2-(Dimethylamino)-1,1-dimethylethyl]-1-piperidinyl]propyl]-
1H-isoindole-1,3(2H)-dione (20ac) The title compound was prepared as
N-[2-(1-Dodecyl-4-piperidinyl)-2-methylpropyl]acetamide (20h) an oil in 59% yield, following Method B starting from 23i (15 g, 81 mmol),
Acetic anhydride (1.9 g, 18.6 mmol) was added dropwise to a solution of N-(3-bromopropyl)phtalimide (24 g, 89.5 mmol) and K2CO3 (28 g, 0.2 mol)
1
20a (4 g, 12.4 mmol) and Et3N (8.6 ml, 62 mmol) in CH2Cl2 (50 ml). The re- in acetonitrile (150 ml). H-NMR (CDCl3) d: 0.72 (6H, s), 1.02—1.16 (2H,
sulting mixture was stirred at room temperature for 20 h. The reaction mix- m), 1.49—1.53 (2H, m), 1.72—1.91 (5H, m), 2.04 (2H, s), 2.25 (6H, s), 2.36
ture was poured into ice-cooled 1 N NaOH, then extracted with CH2Cl2. The
(2H, t, Jϭ6.99 Hz), 2.88—2.92 (2H, m), 3.74 (2H, t, Jϭ6.92 Hz), 7.68—
organic phase was washed with water, dried (MgSO4) and evaporated to af- 7.72 (2H, m), 7.82—7.85 (2H, m). This was converted into its fumarate
ford the title compound (3.9 g, 86%) as a solid: mp 65 °C. 1H-NMR (CDCl3)
d: 0.84—0.90 (9H, m), 1.03—1.11 (1H, m), 1.25—1.47 (22H, m), 1.62—
1.66 (2H, m), 1.81 (2H, m), 2.00 (3H, s), 2.24—2.29 (2H, m), 2.98—3.02
(EtOH): mp 127—134 °C. Anal. (C22H33N3O2·2C4H4O4) C, H, N.
N-[3-[4-[2-(Dimethylamino)-1,1-dimethylethyl]-1-piperidinyl]propyl]-
5-methylhexanamide (20o) A solution of 20ac (14 g, 37.6 mmol) and hy-
(2H, m), 3.14 (2H, d, Jϭ6.24 Hz), 5.40 (1H, br s). This base was converted drazine hydrate (4 ml, 82.5 mmol) in ethanol (100 ml) was heated under re-
into its fumarate (H2O): mp 113 °C. Anal. Calcd for C23H46N2O·C4H4O4: C,
66.11; H, 10.45; N, 5.71. Found: C, 66.09; H, 10.32; N, 5.71.
flux for 0.5 h. The reaction mixture was poured into ice-cooled 5 N sodium
hydroxide, then extracted with EtOAc. The organic layer was washed with
brine, dried over MgSO4 and evaporated to leave 4-[2-(dimethylamino)-1,1-
dimethylethyl]-1-piperidine-propanamine as an oil (7.9 g, 86%). To an ice-
N-[2-(1-Dodecyl-4-piperidinyl)-2-methylpropyl]-N-methylacetamide
(20g) The title compound was prepared as described above from 20b (8 g,
23.8 mmol) in a 97% yield. 1H-NMR (CDCl3) d: 0.86—0.93 (9H, m), cooled solution of 4-[2-(dimethylamino)-1,1-dimethylethyl]-1-piperidine-
1.07—1.47 (23H, m), 1.64—1.73 (2H, m), 1.76—1.86 (2H, m), 2.10 (3H, propanamine (4.2 g, 17.4 mmol) and Et3N (12 ml, 86 mmol) in CH2Cl2
s), 2.24—2.30 (2H, m), 2.98—3.03 (5H, m), 3.22 (0.6H, s), 3.28 (1.4H, s).
(50 ml) was added dropwise a solution of 5-methyl hexanoyl chloride (2.6 g,
The base was converted into its tosylate: mp 102 °C. Anal. Calcd for 17.5 mmol) in CH2Cl2 (25 ml) and the resulting mixture was stirred at room

March 2002
327
temperature overnight. Water was added and the organic layer was washed
with brine, dried over MgSO4 and the solvent was removed in vacuo. The
oily residue was purified by column chromatography eluting with CH2Cl2–
CH3OH–NH4OH (90/9.5/0.5) to afford 20o (2 g, 32%) as an orange oil. This
oil was converted to its corresponding oxalate: mp 87 °C. 1H-NMR (CD3OD,
D2O) d: 1.11 (6H, s), 1.64—1.66 (3H, m), 1.95—1.98 (2H, m), 2.12—2.20
(2H, m), 2.90—2.97 (8H, m), 3.07 (2H, t), 3.15—3.21 (4H, m), 3.62—3.66
(2H, m), 6.65 (4H, s). Anal. (C21H43N3O·2C2H2O4) C, H, N.
b,b,N,N-Tetramethyl-1-(1-oxo-3-phenyl-2-propenyl)-4-piperidine-
ethanamine (20u) To an ice-cold solution of cinnamic acid (6.4 g, 43
mmol) in CHCl3 (100 ml) was added 1,3-dicyclohexylcarbodiimide (DCC,
17.9 g, 87 mmol) and the resulting mixture was stirred at 0 °C for 0.5 h.
A solution of 23i (8 g, 43 mmol) in CHCl3 (50 ml) was added dropwise to
the above solution. The ice bath was removed and the solution was stirred
for 24 h. The reaction mixture was poured into ice-cold 1 N NaOH and ex-
tracted with CH2Cl2. The organic layer was washed with water, dried over
MgSO4 and evaporated. The residue was purified on a silica gel column
(eluent CH2Cl2–CH3OH, 95/5) to afford 7 g (52%) of the title compound: mp
60 °C. 1H-NMR (CDCl3) d: 0.83 (6H, s), 1.27 (2H, m), 1.50—1.80 (3H, m),
2.14 (2H, s), 2.29 (6H, s), 2.60 (1H, t, Jϭ11.6 Hz), 3.07 (1H, t, Jϭ12.4 Hz),
4.16 (1H, d, Jϭ12.9 Hz)), 4.79 (1H, d, Jϭ12.5 Hz), 6.91 (1H, d, Jϭ15.5 Hz),
7.37 (3H, m), 7.52 (2H, m), 7.64 (1H, d, Jϭ15.5 Hz). This solid was con-
verted into its fumarate: mp 169 °C (EtOH). Anal. (C20H30N2O·C4H4O4) C,
H, N.
b,b-Dimethyl-N,N-dimethyl-1-(6,6-dimethyl-2-hepten-4-yn-1-yl)-4-
piperidineethanamine (20p) The title compound was obtained as an oil
in 56% yield starting from 23i (10 g, 54 mmol), 1-bromo-6,6-dimethyl-2-
hepten-4-yne (E/Zϭ3/1, 12 g, 60 mmol), K2CO3 (14.9 g, 0.108 mol) in
1
200 ml of DMF. H-NMR (CDCl3) d: 0.83 (6H, s), 1.17—1.39 (11H, m),
1.59—1.63 (2H, m), 1.88 (2H, t, Jϭ11.41 Hz), 2.12 (2H, s), 2.27 (3H, s),
2.28 (3H, s), 2.93—3.00 (5H, m), 5.57—5.62 (1H, m), 5.90—6.11 (1H, m).
The maleate was prepared and recrystallized from ethanol: mp 192 °C. Anal.
(C20H36N2·2C4H4O4) C, H, N.
b,b,N,N-Tetramethyl-1-(3-phenyl-2-propenyl)-4-piperidineethan-
amine (20v) The above compound (3.85 g, 12 mmol) was reduced with
3.5 M solution of RedAl (7 ml, 24 mmol) in toluene (70 ml) following
b,b-Dimethyl-N,N-dimethyl-1-(2,2-dimethylheptyl)-4-piperidine-
ethanamine (20n) A solution of 20p (4.5 g, 14.7 mmol) in methanol
(150 ml) and 10% Pd/C was hydrogenated in a Parr apparatus at 40 °C under
50 psi of hydrogen pressure for 8 h. Catalyst was removed by filtration and
the solvent was evaporated in vacuo to give 20n as an oil. 1H-NMR (CDCl3)
d: 0.83—0.87 (15H, m), 1.12—1.64 (13H, m), 1.89 (2H, m), 2.12 (2H, s),
2.28—2.34 (8H, m), 3.02—3.06 (2H, m). The fumarate was prepared in
ethanol: mp 138 °C. Anal. (C20H42N2·2C4H4O4) C, H, N.
1
method G, to provide 20v (3.5 g, 95%). H-NMR (CDCl3) d: 0.83 (6H, s),
1.2—1.4 (3H, m), 1.64 (2H, m), 1.92 (2H, t, Jϭ11.3 Hz), 2.12 (2H, s), 2.28
(6H, s), 3.04 (2H, d, Jϭ17.8 Hz), 3.12 (2H, d, Jϭ6.7 Hz), 6.30 (1H, dt,
Jϭ15.9, 6.7 Hz), 6.49 (1H, d, Jϭ15.9 Hz), 7.10—7.45 (5H, m). This oily
compound was converted into its fumarate (iso-PrOH): mp 150 °C. Anal.
(C20H32N2·2C4H4O4) C, H, N.
4-[2-(Dimethylamino)-1,1-dimethylethyl]-N-(4-methylpentyl)-1-
piperidinebutanamide 20q A solution of 23i (12 g, 65 mmol), 4-bro-
mobutanoic acid ethyl ester (15.9 g, 81 mmol)) and K2CO3 (22.4 g, 0.16 mol)
in CH3CN (200 ml) was refluxed for 4 h. After cooling, the solvent was
evaporated, water was added to the resulting residue and the mixture was ex-
tracted with EtOAc. The organic phase was washed with brine, dried
(MgSO4) and evaporated to give 4-[2-(dimethylamino)-1,1-dimethylethyl]-1-
piperidinebutanoic acid ethyl ester 20ad (11.8 g, 61%) as a yellow oil. A so-
lution of 20ad (4 g, 12 mmol) and 4-methyl pentanamine (9 g, 90 mmol) in
toluene (100 ml) was heated in an autoclave at 200 °C for 4 d. After cooling,
solvent was evaporated and the oily residue was purified by silica gel col-
umn chromatography with CH2Cl2–CH3OH (95/5) as eluent to give 20q (3
1-[2-(4-Chlorophenoxy)-2-methyl-1-oxopropyl]-b,b,N,N-tetramethyl-
4-piperidineethaneamine (20w) The title compound was prepared as de-
scribed for 20u, starting from 23i (8 g, 43 mmol), DCC (17.95 g, 87 mmol)
and 2-(4-chlorophenoxy)-2-methyl-propanoic acid (9.2 g, 43 mmol) in
CHCl3 (100 ml) to provide 9.9 g (60%) of 20w: mp 63 °C. 1H-NMR (CDCl3)
d: 0.67 (3H, s), 0.69 (3H, s), 1.05 (1H, dq, Jϭ12.5, 3.6 Hz), 1.42 (2H, m),
1.62 (3H, s), 1.65 (3H, s), 1.60—1.70 (2H, m), 1.97 (1H, d, Jϭ13 Hz), 2.03
(1H, d, Jϭ13 Hz), 2.23 (6H, s), 2.44 (1H, t, Jϭ10.6 Hz), 2.79 (1H, t,
Jϭ12.7 Hz), 4.70 (2H, t, Jϭ12.8 Hz), 6.77 (2H, d, Jϭ9.0 Hz), 7.16 (2H, d,
Jϭ9.0 Hz). This was converted into its fumarate (EtOH): mp 194 °C. Anal.
(C21H33ClN2O2·C4H4O4) C, H, N.
1-[2-(4-Chlorophenoxy)-2-methylpropyl]-b,b,N,N-tetramethyl-4-
piperidineethaneamine (20x) Reduction of 20w (4.5 g, 11.8 mmol) with
3.5 M solution of RedAl (6.8 ml, 23.6 mmol) following Method G gave 3.6 g
1
g, 71%) as an oil. H-NMR (CDCl3) d: 0.83 (6H, s), 0.88 (6H, d, Jϭ6.60
Hz), 1.15—1.29 (5H, m), 1.50—1.68 (7H, m), 1.83—1.92 (2H, m), 2.12
(2H, s), 2.22 (2H, t, Jϭ7.12 Hz), 2.28 (6H, s), 2.33 (2H, t, Jϭ6.78 Hz),
2.94—2.98 (2H, m), 3.17—3.23 (2H, m), 6.74 (1H, br s). This was con-
verted to its fumarate in EtOH: mp 140 °C. Anal. (C21H43N3O·2C4H4O4) C,
H, N.
1
(83%) of 20x as an oil. H-NMR (CDCl3) d: 0.83 (6H, s), 1.15—1.40 (3H,
m), 1.25 (6H, s), 1.55 (2H, d, Jϭ12.2 Hz), 2.10 (2H, s), 2.18 (2H, d,
Jϭ11.2 Hz), 2.28 (6H, s), 2.45 (2H, s), 2.98 (2H, d, Jϭ17.5 Hz), 6.92 (2H, d,
Jϭ8.8 Hz), 7.20 (2H, d, Jϭ8.8 Hz). This was transformed into its fumarate:
mp 110 °C. Anal. (C21H35ClN2O·2C4H4O4) C, H, N. 13C-NMR (DMSO-d6)
d: 22.86, 24.50, 26.07, 36.35, 42.06, 47.68, 55.93, 66.74, 67.56, 81.54,
124.86, 126.80, 128.77, 134.21, 153.78, 166.39.
b,b-Dimethyl-N,N-dimethyl-1-[(4-methylpentyl)aminobutyl]-4-
piperidineethanamine (20r) The title compound was prepared following
procedure G from 20q (2 g, 5.7 mmol) in 83% yield as an oil. 1H-NMR
(CDCl3) d: 0.83 (6H, s), 0.87 (6H, d, Jϭ6.6 Hz), 1.1—1.5 (13H, m), 1.59
(2H, t, Jϭ10.8 Hz), 1.83 (2H, t, Jϭ11.0 Hz), 2.11 (2H, s), 2.28 (6H, s),
2.25—2.35 (2H, m), 2.58 (4H, m), 2.99 (2H, d, Jϭ11.5 Hz). This was con-
verted to its corresponding fumarate (EtOH): mp 130—142 °C. Anal.
(C21H45N3·3C4H4O4) C, H, N.
b,b,N,N-Tetramethyl-1-(1-oxododecyl)-4-piperidineethanamine (20s)
A solution of the acetate salt of 23i (8.28 g, 45 mmol) and Et3N (22.7 ml,
0.225 mol) in CH2Cl2 (400 ml) was cooled at 5 °C. Dodecanoic acid chloride
(15.5 ml, 67 mmol) was added dropwise and the resulting mixture was
stirred for 24 h. The reaction mixture was poured into ice-cooled 1 N NaOH
solution and extracted with EtOAc. The organic phase was washed with
water, dried (MgSO4) and concentrated. The residue was purified by chro-
matography (eluent CH2Cl2–CH3OH, 98/2) to give 20s (11 g, 66%) as an oil.
1H-NMR (CDCl3) d: 0.81 (3H, s), 0.82 (3H, s), 0.87 (3H, t, Jϭ6.4 Hz),
1.1—1.4 (20H, m), 1.5—1.7 (4H, m), 2.12 (2H, s), 2.28 (6H, s), 2.30 (1H,
m), 2.44 (1H, t, Jϭ11.5 Hz), 2.94 (1H, t, Jϭ12.3 Hz), 3.90 (1H, d,
Jϭ12.9 Hz), 4.70 (1H, d, Jϭ12.5 Hz). This compound was converted into its
oxalate: mp 138 °C. Anal. (C23H46N2O·C2H2O4) C, H, N.
b,b,N,N-Tetramethyl-1-[2(S)-(6-methoxy-2-naphtalenyl)-1-oxo-
propyl]-4-piperidineethaneamine (20y) Acylation of 23i (8 g, 43 mmol)
with (S)-(ϩ)-6-methoxy-a-methyl naphtaleneacetic acid (9.9 g, 43 mmol) in
the presence of DCC (17.5 g, 86 mmol) in CHCl3 (100 ml) provided 20y as
an oil (9.9 g, 58%). This compound was transformed into an oxalate (EtOH):
1
mp 169 °C. H-NMR (DMSO-d6, T: 400 °K) d: 0.67 (6H, s), 0.6—0.8 (1H,
m), 1.03 (1H, dq, Jϭ8.7, 3.9 Hz), 1.37 (3H, d, Jϭ6.7 Hz), 1.3—1.45 (2H,
m), 1.58 (1H, bd), 1.98 (2H, s), 2.05 (3H, s), 2.15 (3H, s), 2.54 (1H, m), 2.66
(1H, m), 3.86 (3H, s), 4.14 (1H, q, Jϭ6.7 Hz), 4.27 (2H, m), 7.11 (1H, d,
Jϭ8.9 Hz), 7.22 (1H, s), 7.34 (1H, d, Jϭ8.6 Hz), 7.62 (1H, s), 7.71 (2H, d,
Jϭ8.6 Hz). Anal. (C25H36N2O2·C2H2O4) C, H, N.
b,b,N,N-Tetramethyl-1-[2(S)-(6-methoxy-2-naphtalenyl)propyl]-4-
piperidineethaneamine (20z) Following Method G, the compound 20y
(6 g, 15 mmol) was reduced with 3.5 M RedAl solution (13 ml, 45 mmol) to
afford 20z (6 g, 100%) as a white solid: mp 70 °C. 1H-NMR (CDCl3) d: 0.81
(6H, s), 1.2—1.4 (3H, m), 1.33 (3H, d, Jϭ6.8 Hz), 1.55 (2H, d, Jϭ11.7 Hz),
1.79 (1H, t, Jϭ10.3 Hz), 1.96 (1H, t, Jϭ10.3 Hz), 2.10 (2H, s), 2.26 (6H, s),
2.49 (2H, m), 2.92 (1H, d, Jϭ10.3 Hz), 3.00 (1H, d, Jϭ17.9 Hz), 3.06 (1H,
m), 3.90 (3H, s), 7.11 (2H, m), 7.32 (1H, d, Jϭ8.4 Hz), 7.56 (1H, s), 7.67
(2H, m). This was converted into its fumarate (EtOH): mp 166 °C. Anal.
(C25H38N2O·2C4H4O4) C, H, N.
b,b,N,N-Tetramethyl-1-[2-[4-(2-methylpropyl)phenyl]-1-oxopropyl]-4-
piperidineethaneamine (20aa) Acylation of 23i (8 g, 43 mmol) with 4-
isobutyl-a-methylphenylacetic acid (8.95 g, 43 mmol) in CHCl3 (100 ml) in
the presence of DCC (17.9 g, 86.8 mmol) gave 12 g (74%) of 20aa as an oil.
1H-NMR (CDCl3) d: 0.17 (0.5H, dq, Jϭ8.5, 4.1 Hz), 0.60 (3H, s), 0.63 (3H,
s), 0.80 (3H, s), 0.86 (3H, d, Jϭ5.8 Hz), 0.91 (3H, d, Jϭ5.8 Hz), 1.01 (0.5H,
dq, Jϭ8.5, 4.1 Hz), 1.15—1.25 (2H, m), 1.40 (1.5H, d, Jϭ6.2 Hz), 1.42
b,b,N,N,N-Pentamethyl-1-(1-oxododecyl)-4-piperidineethaniminium
Iodide (20t) Methyl iodide (10 ml, 0.15 mol) was added to a solution of
20s (1 g, 2.72 mmol) in ether (20 ml). The resulting mixture was stirred for
48 h at room temperature and 10 h at reflux. After cooling, the mixture was
1
filtered to give 20t as a white solid: mp 208 °C. H-NMR (CDCl3) d: 0.87
(3H, t, Jϭ6.4 Hz), 1.1—1.4 (26H, m), 1.28 (6H, s), 1.4—1.65 (4H, m), 1.85
(1H, d, Jϭ12.9 Hz), 1.93 (1H, d, Jϭ11.0 Hz), 2.33 (2H, t, Jϭ7.9 Hz)), 2.44
(1H, t, Jϭ12.7 Hz), 2.96 (1H, t, Jϭ11.9 Hz), 3.58 (9H, s), 3.70 (1H, d,
Jϭ13.8 Hz), 3.80 (1H, d, Jϭ13.8 Hz), 3.97 (1H, d, Jϭ13.4 Hz), 4.70 (1H, d,
Jϭ12.8 Hz). Anal. (C24H49IN2O) C, H, N.

328
Vol. 50, No. 3
(1.5H, d, Jϭ6.2 Hz), 1.40—1.70 (2H, m), 1.75—1.90 (0.5H, m), 1.95 (0.5H,
m), 2.21 (3H, s), 2.25 (3H, s), 2.45 (3H, m), 2.83 (0.5H, t, Jϭ10.4 Hz),
3.8—3.95 (1.5H, m), 4.73 (1H, m), 7.05—7.20 (4H, m). This compound
was converted into its fumarate (iso-PrOH): mp 172 °C. Anal.
(C24H40N2O·C4H4O4) C, H, N.
ligand corresponding to our needs. Furthermore, the superimposition of the
Ca of the three X-ray structures, revealed that their backbones are ab-
solutely superimposable. We considered then that the 2SQC and 3SQC will
not give us more information. Using the sequence alignment of squalene-
hopene cyclase and OSC proposed by Wendt et al.4a) we transferred the co-
ordinates in the non-gapped regions from the squalene-hopene cyclase to our
OSC model. The gapped regions were processed by adding loops from the
PDB, using the functionality loop search of the Homology module. Ten
loops propositions were retrieved, and the most suitable one was chosen on
the basis of compatibility with the conformation of the flanking regions. The
obtained model was submitted to a refinement procedure: a complete relax-
ation by an energy minimization followed by a succession of mild Molecular
Dynamics simulations (10 ps) in order to detect eventual steric constraints or
bumps. Finally, a complete relaxation by energy minimization was per-
formed to get our final 3D OSC model.
b,b,N,N-Tetramethyl-1-[2-[4-(2-methylpropyl)phenyl]propyl]-4-
piperidineethaneamine (20ab) Following Method G, 20aa (6 g,
16.1 mmol) was reduced with a 3.5 N RedAl solution (14 ml, 48.3 mmol) to
provide 5.1 g (88%) of 20ab as an oil. This compound was converted into its
1
fumarate (EtOH): mp 145 °C. H-NMR (DMSO-d6) d: 0.78 (6H, s), 0.84
(6H, d, Jϭ6.60 Hz), 1.17 (3H, d, Jϭ6.84 Hz), 1.25 (3H, m), 1.54—1.57 (2H,
m), 1.74—1.83 (1H, m), 2.00—2.15 (2H, m), 2.20 (2H, s), 2.28 (6H, s,
N(CH3)2), 2.39 (2H, d, Jϭ7.13 Hz), 2.49—2.50 (2H, m), 2.58—2.59 (2H,
m), 2.95—3.10 (3H, m), 6.57 (4H, s), 7.05—7.15 (4H, dd, Jϭ8.04, 22.5 Hz).
Anal. (C24H42N2·2C4H4O4) C, H, N.
3-(4-Pyridinyl)-2-piperidinone (26) A solution of 25 (3 g, 13.8 mmol)
and Raney nickel (0.5 g) in EtOH (30 ml) saturated with ammonia was hy-
drogenated in a Parr apparatus at 50 °C under 50 psi hydrogen pressure for
8 h. Catalyst was removed by filtration and the filtrate was concentrated in
vacuo to give 26 (1.9 g, 80%) as a solid: mp 164 °C (EtOAc). 1H-NMR
(CDCl3) d: 1.80—1.99 (3H, m, H-4, H-5), 2.15—2.25 (1H, m, H-4a), 3.41—
3.46 (2H, m, H-6), 3.60—3.65 (1H, dd, Jϭ5.8, 6.9 Hz, H-3), 6.53 (1H, br s,
CONH), 7.17—7.19 (2H, m), 8.55—8.57 (2H, m).
Docking of the Inhibitors: The Affinity procedure was applied using all
the parameters as default values. The first step consisted in defining the ac-
tive site, and positioning the inhibitor so that its exocyclic nitrogen atom was
superimposed to the nitrogen of LDAO, while their cores were aligned with
the LDAO alkyl chain. After performing energy minimization and a short
molecular dynamics on the protein-inhibitor system to remove bad internal
coordinates and contact, the core procedure was performed which gave our
3D OSC-inhibitor models.
3-(4-Piperidinyl)-2-piperidinone (27) The title compound was hydro-
genated from 26 as described for 4-piperidineethanamine derivative in a
93% yield (8.5 g, 48.3 mmol): mp 136 °C. H-NMR (CDCl3) d: 1.29—1.72
(6H, complex m), 1.82—1.92 (2H, m), 2.08 (1H, s, NH), 2.21—2.32 (2H,
m), 3.05—3.13 (2H, m), 2.61 (1H, dd, Jϭ2.45, 11.9 Hz), 2.69 (1H, dd,
Jϭ2.9, 11.6 Hz), 3.05—3.13 (2H, m), 3.23—3.28 (2H, m), 6.10 (1H, s,
NHCO).
Preparation of Rat Liver Microsomal 2,3-Oxidosqualene Cyclase
Male Wistar rats weighing 250 g were used. Food was withdrawn 4 h before
animals were killed. The livers were quickly removed, minced and homoge-
nized in ice cold 0.25 M sucrose in a Potter-Elvehjem type Teflon homoge-
1
nizer at 2000 rpm. Homogenates were centrifuged for 15 min at 16000 gmax
,
and the supernatants collected were centrifuged again at 16000 gmax. Then
the two-thirds upper part of the supernatant was collected and centrifuged at
1000000 gmax for 1 h. Microsomal pellets were resuspended in one-half the
initial volume and then centrifuged for 1 h at 100000 gmax. Pellets of washed
microsomes were collected and fractionated in small aliquots stored at
Ϫ80 °C without loss of activity for at least 2 months.
2,3-Oxidosqualene Cyclase Assay We used the original following pro-
cedure: a standard assay mixture consisted of a total volume of 500 ml con-
taining 150 mg of microsomal protein and 100 mM (R,S)-2,3-oxidosqua-
lene.23) Incubation was for 1 h at 37 °C; then the reaction was stopped by
adding 1 ml of 7% methanolic KOH and 20 ng of stigmasterol as internal
standard. After 0.5 h at 80 °C for saponification, nonsaponifiable lipids were
extracted twice with n-hexane and then evaporated and derivatized with
75 ml of BSTFA–1% TMCS and 25 ml of pyridine. TMCS ethers were chro-
matographed on a 30 m OV1 column at 260 °C. Retention times of TMCS-
lanosterol and -stigmasterol ethers were respectively 17 min and 15.5 min.
The inhibitory potencies of compounds were expressed as the concentration
at which 50% inhibition of OSC activity was observed.
3-(4-(1-Dodecylpiperidin-4-yl)-2-piperidinone (28) The title com-
pound was obtained following Method B from 27 (4 g, 21.8 mmol) as a solid
1
(7 g, 91%): mp 90 °C (iso-Pr2O). H-NMR (CDCl3) d: 0.87 (3H, t, Jϭ6.4
Hz, CH3), 1.25 (20H, complex m), 1.38—1.74 (6H, m), 1.82—1.99 (4H, m),
2.15—2.31 (4H, m), 2.92—3.00 (2H, m), 3.24—3.27 (2H, m), 5.80 (1H, s).
Anal. (C22H42N2O) C, H, N.
3-(4-(1-Dodecylpiperidin-4-yl)piperidine (21a) To an ice-cooled sus-
pension of LiAlH4 (0.955 g, 25 mmol) in THF (100 ml) was carefully added
a solution of 28 (4 g, 11.4 mmol) in THF (50 ml) and the resulting mixture
was allowed to warm to ambient temperature then it was stirred under reflux
for 3 h. After cooling the mixture was hydrolyzed with a 10% aqueous solu-
tion of Rochelle salt. The resulting precipitate was filtered off and washed
with THF. The combined filtrates were evaporated to give 21a as a solid
(3.7 g, 97%). This compound was converted to the corresponding fumarate:
mp 176 °C. 1H-NMR (DMSO-d6, D2O) d: 0.85 (3H, t, Jϭ6.4 Hz, CH3),
1.18—1.59 (30H, complex m), 1.76—1.87 (2H, m), 2.33 (6H, s), 2.71—
2.83 (2H, m), 2.93—2.98 (2H, m), 3.21—3.26 (2H, m), 3.44—3.48 (2H, m),
7.23 (4H, d, Jϭ8.10 Hz), 7.55 (4H, d, Jϭ8.10 Hz). (C22H44N2·2C7H8O2S) C,
H, N.
Acknowledgment The authors thank Corinne Grandvincent, Sylvie
Célimène for the synthetic work, Gilles Martin-Gousset for the spectral
analyses and Paule Fontet for the biological experiments.
1-Methyl-3-(4-(1-dodecylpiperidinyl)piperidine (21b) A solution of
21a as a base (2.1 g, 6.25 mmol), formic acid (15 g) and a 37% solution of
formaldehyde in methanol (12 g) was stirred at 100 °C overnight. The reac-
tion mixture was evaporated and the residue was carefully basified with 30%
sodium hydroxide then the mixture was extracted with EtOAc. The organic
phase was washed with water, dried (MgSO4). Evaporation of the solvent
References and Notes
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1
left 21b as an oil (2.1 g, 95%). H-NMR (CDCl3) d: 0.81—0.93 (4H, m),
1.01—1.11 (1H, m), 1.25—1.84 (32H, complex m), 2.24—2.28 (5H, m,
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Molecular Modeling Studies Software and Hardware: All simulations
were performed with the Insight II 98.0/Discover 2.98 modeling package.
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