Identification of MK-944a: A second clinical candidate from the hydroxylaminepentanamide isostere series of HIV protease inhibitors

Article abstract of DOI:10.1021/jm9903848

Recent results from human clinical trials have established the critical role of HIV protease inhibitors in the treatment of acquired immune-deficiency syndrome (AIDS). However, the emergence of viral resistance, demanding treatment protocols, and adverse side effects have exposed the urgent need for a second generation of HIV protease inhibitors. The continued exploration of our hydroxylaminepentanamide (HAPA) transition-state isostere series of HIV protease inhibitors, which initially resulted in the identification of Crixivan (indinavir sulfate, MK-639, L-735,524), has now yielded MK-944a (L-756,423). This compound is potent, is selective, and competitively inhibits HIV-1 PR with a K(i) value of 0.049 nM. It stops the spread of the HIV(IIIb)-infected MT4 lymphoid cells at 25.0-50.0 nM, even in the presence of α₁ acid glycoprotein, human serum albumin, normal human serum, or fetal bovine serum. MK-944a has a longer half-life in several animal models (rats, dogs, and monkeys) than indinavir sulfate and is currently in advanced human clinical trials.

Full text of DOI:10.1021/jm9903848

3386
J . Med. Chem. 2000, 43, 3386-3399
Id en tifica tion of MK-944a : A Secon d Clin ica l Ca n d id a te fr om th e
Hyd r oxyla m in ep en ta n a m id e Isoster e Ser ies of HIV P r otea se In h ibitor s
Bruce D. Dorsey,*,† Colleen McDonough,† Stacey L. McDaniel,† Rhonda B. Levin,†,§ Christina L. Newton,†
J acob M. Hoffman,† Paul L. Darke,‡ J oan A. Zugay-Murphy,‡ Emilio A. Emini,‡ William A. Schleif,‡
David B. Olsen,‡ Mark W. Stahlhut,‡ Carrie A. Rutkowski,‡ Lawrence C. Kuo,‡ J iunn H. Lin,§ I-W. Chen,§
Stuart R. Michelson,§ M. Katharine Holloway,| J oel R. Huff,† and J oseph P. Vacca†
Departments of Medicinal Chemistry, Antiviral Research, Drug Metabolism, and Molecular Systems,
Merck Research Laboratories, West Point, Pennsylvania 19486
Received J uly 26, 1999
Recent results from human clinical trials have established the critical role of HIV protease
inhibitors in the treatment of acquired immune-deficiency syndrome (AIDS). However, the
emergence of viral resistance, demanding treatment protocols, and adverse side effects have
exposed the urgent need for a second generation of HIV protease inhibitors. The continued
exploration of our hydroxylaminepentanamide (HAPA) transition-state isostere series of HIV
protease inhibitors, which initially resulted in the identification of Crixivan (indinavir sulfate,
MK-639, L-735,524), has now yielded MK-944a (L-756,423). This compound is potent, is
selective, and competitively inhibits HIV-1 PR with a Ki value of 0.049 nM. It stops the spread
of the HIVIIIb-infected MT4 lymphoid cells at 25.0-50.0 nM, even in the presence of R1 acid
glycoprotein, human serum albumin, normal human serum, or fetal bovine serum. MK-944a
has a longer half-life in several animal models (rats, dogs, and monkeys) than indinavir sulfate
and is currently in advanced human clinical trials.
In tr od u ction
HIV-infected patients with prior antiretroviral expo-
sure.5 Both of these studies support the recent guide-
lines7 for treatment of HIV disease which recommend
early initiation of antiretroviral therapy; this includes
the use of two nucleoside reverse transcriptase inhibi-
tors and a protease inhibitor. Promising results have
been presented for four other Food and Drug Adminis-
tration approved HIV PR inhibitors: saquinavir mesy-
late,8 ritonavir,9 nelfinavir mesylate,10 and amprenavir.11
Conclusions drawn from all these studies suggest that
we have entered into a new era for the treatment of
AIDS.
Although these HIV PR inhibitors represent a major
advance in the management of HIV disease, the dif-
ficulties in compliance with the treatment protocols,
adverse side effects,8c,9c,10c,11,12 and viral resistance13
have encouraged medicinal chemistry researchers to
develop second-generation inhibitors. To overcome these
clinical concerns, the next generation HIV PR inhibitors
should have improved in vitro and in vivo properties
(i.e. improved potency against the enzyme, efficacy in a
cell-based assay in the presence of biologically relevant
protein, and improved pharmacokinetic parameters in
animal models). Therefore, the criteria for a clinical
backup to indinavir, the most widely prescribed HIV PR
inhibitor in the world, would require a compound that
addressed these aforementioned concerns. Herein, we
disclose the development of a second clinical candidate
from our hydroxylaminepentanamide (HAPA) isostere
series of HIV PR inhibitors.
Human immunodeficiency virus (HIV), the etiologic
agent of acquired immune-deficiency syndrome (AIDS),
is a member of the Lentiviridae subfamily of retro-
viruses that contain three major genes (gag, pol, env).1
Products of the gag gene include structural proteins of
the virus nucleocapsid; the pol gene encodes three
enzymes: a protease, a reverse transcriptase, and an
endonuclease; and the env gene encodes the membrane
proteins of the mature virus.2 The gag and pol gene
products are expressed as polyproteins that are pro-
cessed by the HIV protease (PR), an essential step for
virus maturation. In 1988, Sigal and others3 determined
that a functioning aspartyl protease was required for
HIV replication. Throughout 1997-1998, Merck re-
searchers and their colleagues have disclosed several
landmark publications4,5 which describe the clinical
results of the treatment of HIV-infected patients using
the potent protease inhibitor Crixivan (indinavir sul-
fate)6 in combination with two nucleoside reverse tran-
scriptase inhibitor analogues (zidovudine and lamivu-
dine). These studies demonstrate that triple-combination
therapy using indinavir, zidovudine, and lamivudine:
(1) significantly slows the progress of HIV-1 disease in
patients with 200 CD4 cells or less as compared with
therapy using zidovudine and lamivudine alone4 and (2)
reduces the levels of HIV RNA to less than 500 copies/
mL for as long as 100 weeks, in 78% of the contributing
* To whom correspondence should be addressed at: Merck Research
Laboratories, Box 4, WP14-3, West Point, PA 19486. Phone: 215-652-
3089. Fax: 215-652-3971. E-mail: bruce•dorsey@merck.com.
† Department of Medicinal Chemistry.
Design Ra tion a le
Previous work has described the design strategy
which led to the introduction of the HAPA transition-
state isostere and resulted in the identification of
‡ Department of Antiviral Research.
§ Department of Drug Metabolism.
| Department of Molecular Systems.
10.1021/jm9903848 CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/22/2000

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3387
Ch a r t 1
Ch a r t 2. Disposition of Indinavir after Oral Dosing in Humans
indinavir.14 The effects of placing large lipophilic het-
erocycles in the S3 enzyme site in combination with a
pyridyl P1′ ligand (Chart 1) has been described in a
subsequent publication.15 This research resulted in the
identification of L-748,496, a potent, selective, and orally
bioavailable protease inhibitor with pharmacokinetic
profiles in rats, dogs, and monkeys comparable to those
with indinavir. However, this compound did not dem-
onstrate a pharmacokinetic half-life improvement over
indinavir in several animal models. Human clinical
studies have established that indinavir must be dosed
every 8 h at a dose of 800 mg.12 L-748,496 would not
address the issue of an improved treatment protocol and
consequently was dropped from further consideration.
The report of disposition of [14C]indinavir after oral
dosing in humans has recently been disclosed.16 In
summary, the metabolites found in both the urine and
feces were the oxidative N-dealkylation of the 3-pyridyl-
methyl ligand M1, the quaternary pyridine N-glucu-
ronide M3, the pyridine N-oxide M4, the hydroxylated
aminohydroxyindan M2, M5, and derivatives thereof
(Chart 2). These metabolism results combined with our
reported structure-activity relationships suggested that
one strategy to improve upon the pharmacokinetics of
indinavir sulfate would be to block or avoid these
metabolic pathways. Therefore, replacement of the
metabolically labile 3-pyridylmethyl with either a large
lipophilic heterocycle or a modified pyridine ring might
provide a compound with a significantly longer half-life
in animals. Toward this end, a series of 3-pyridylmethyl
replacement analogues possessing a wide range of
physical properties were designed and synthesized.
for the selection of a backup candidate. In one drug
candidate, several parameters would have to be opti-
mally balanced. First, the requirements for potency (less
than 1 nM IC50) against HIV-1 protease,6 and potency
in our cell-based assay6 in the presence of biologically
relevant proteins (IC95 value of less than 100 nM, as
defined by the minimum inhibitor concentration of drug
needed to inhibit 95% of replication of virus in MT4
human T-lymphoid cells infected with the IIIb isolate),
had to be achieved. Protein binding can play a deleteri-
ous role in the efficacy of protease inhibitors as dem-
onstrated in the viral spread assay.17 The negative
consequence of protein binding would have to be criti-
cally evaluated in the selection of a backup candidate.
Compound solubilities in water were also measured and
compared to that of indinavir (70 µg/mL at pH 7.4,
phosphate buffer) because of the previously established
relationship of solubility to oral bioavailability.14 How-
ever, the most critical assay used for selection of a
second clinical candidate was the determination of drug
concentration in plasma after oral administration to
dogs at a 10 mg/kg dose as a citric acid solution. Our
criteria for success in this pharmacokinetic assay were
plasma concentration maximum (Cmax) levels of at least
10 µM and maintaince of drug concentrations after 8 h
(C8h) of 10-fold greater than the drug’s IC95 value
(adjusted to include the negative effects of protein
binding).
Ch em istr y
The synthesis of the versatile penultimate intermedi-
ate 2 has been previously described.14,18 Scheme 1
illustrates two general methods developed to obtain the
3-pyridylmethyl analogues 3-8 (Table 1). First, a
reductive amination protocol (method A) using quino-
line-3-carboxaldehyde, amine 2, and sodium triacetoxy-
Selection Cr iter ia
Also, to improve upon the impressive clinical results
of indinavir, we needed to establish stringent criteria

3388 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Sch em e 1. Synthesis of Analogues 3-8a
Dorsey et al.
a
Reagents and conditions: (a) TMSCHN2, CHCl3, CH3OH; (b) DIBAL-H, THF; (c) SOCl2, CH2Cl2; (d) 1, Et3N, DMF; (e) 2, quinoline-
3-carboxaldehyde, NaB(OAc)3H, AcOH.
Ta ble 1. 3-Pyridylmethyl Analogues 3-8
a
b
c
All entries are for n ) 1 except where noted; data are the mean ( SEM. Solubility determined at pH 7.4 in µg/mL. Cmax, maximum
plasma concentration; C8h, concentration after 8 h. Bioavailability in dogs, each compound was delivered orally in 0.05 M citric acid at 10
mg/kg. For all cases n ) 2, except where noted. Average determination was 50.5 nM.
d
borohydride in dichloroethane with a catalytic amount
of acetic acid would provide target 3. Alternatively, a
procedure (method B) was developed which utilized the
N-alkylation of piperazine 2 with an arylchloromethyl
1, prepared from the commercially available arylcar-
boxylic acids via esterification, reduction, and activation
as the chloromethyl electrophile. This would provide
analogues 4-8 which represent the substituted 3-py-
ridylmethyl analogues prepared in Table 1. Also, this
procedure was generalized to include the chloromethyl
electrophiles described in Scheme 2 and used to prepare
11, 13, 15, 16, and 18.
As illustrated in Scheme 2, intermediate 1019 was
decarboxylated with copper(I) oxide in quinoline; then
the ester functionality was reduced with DIBAL-H and
converted into the chloromethyl electrophile 11 with
thionyl chloride. The Boc-protected 3-aminofuran 12
was deprotected in hydrochloric acid and zinc chloride
and condensed with ethoxycarbonylmalonaldehyde, fol-
lowing the method of Torii.20 The resulting ethyl furo-
[2,3-b]pyridine-3-carboxylate was reduced and activated
as previously described. Electrophiles 15 and 16 were
prepared starting with the commercially available ester
14. Reductive cleavage of the chlorine with zinc in acetic
acid, followed by reduction of the ester functionality and
activation, provided 16. Compound 15 was prepared in
an analogous manner. These electrophiles were reacted
with piperazine 2 to provide analogues 19, 22, 24, and
25, as illustrated in Table 2.
The acid functionality of furo[2,3-b]pyridine-2,5-di-
carboxylic acid 5-ethyl acid 17 could be activated with
isobutyl chloroformate and selectively reduced with
sodium borohydride. The alcohol was then treated with
thionyl chloride to provide electrophile 18 which was
reacted with piperazine 2 to provide analogue 30, as
illustrated in Table 3. The remaining derivatives in
Table 3 were prepared from known arylaldehydes or
manipulations of the targets as described in the Ex-
perimental Section.
Resu lts a n d Discu ssion
Table 1 illustrates our attempts to modify the 3-py-
ridyl P3 moiety of indinavir and to explore what the
effects of these modifications had on pharmacokinetics
in dogs. As noted, most of these analogues fulfilled our
requirements of potency. The quinoline analogue 3

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3389
Ta ble 2. Pyridyl Heterocycles 19-25
a
b
All entries are for n ) 1 except where noted; data are the mean ( SEM. Solubility determined at pH 7.4 in µg/mL, for indinavir (70
µg/mL). c Clog P for indinavir was 2.44, and the measured log P was 2.92. Bioavailability in dogs, each compound was delivered orally
d
in 0.05 M citric acid at 10 mg/kg. For all cases n ) 2, except where noted. e Average determination was 17.4 nM. f Delivered at 5 mg/kg.
Sch em e 2. Synthesis of Heterobicyclic Chloromethyl
Having had limited success with simple substituted
pyridine analogues, attention was turned to the incor-
poration of pyridine-based bicyclic heterocycles into the
S3 pocket. The hypothesis was that a modified pyridine
bicyclic ring could balance lipophilicity and solubility
of the molecule and at the same time redirect the route
of metabolism away from either N-dealkylation of the
arylmethyl moiety or N-glucuronidation of the pyridine
nitrogen. Table 2 illustrates attempts in this regard.
Upon the basis of the previous success of [2,3-b]- and
[3,2-b]thienothiophenes,15 the [2,3-b]- and [3,2-b]furo-
pyridine moieties were incorporated into the S3 pocket.
Contrary to the thienothiophenes, the furopyridine ring
contains a weakly basic nitrogen which should provide
the target analogues with some aqueous solubility. The
4-chlorofuropyridine 19, a synthetic intermediate to the
parent series, provided the potency required in the cell-
based assay. Importantly, significant amounts of com-
pound 19 could be detected in the plasma of dogs at 8 h
after an oral dosing, exceeding our requirement of a C8h/
IC95 ratio of 10. Removal of the chlorine atom then
provided the parent [2,3-b]furopyridine 20, L-754,394.
This compound also maintained potency and reached
drug plasma levels of almost 10 µM at 8 h after oral
dosing in dogs and could still be detected in plasma at
approximately 1 µM after 24 h.21 The isomeric [3,2-b]-
furopyridine 22 demonstrated similar potency and
excellent pharmacokinetics. Acylation of the piperazine
ring with furo[2,3-b]pyridine-5-carboxylic acid resulted
in a compound with a greatly reduced pharmacokinetic
profile, analogue 23. Interestingly, reduction of the
olefin of furopyridine 20 provided analogue 21 which,
although potent, did not provide the pharmacokinetic
results seen with furopyridine 20. Two azaindazoles, 24
and 25, were also prepared but did not provide useful
oral bioavailability.
Reagentsa
a
Reagents and conditions: (a) quinoline, Cu, 210-230 °C; (b)
DIBAL-H, THF; (c) SOCl2, CH2Cl2; (d) NMM, ClCO2CH2CH(CH3)2,
then NaBH4, H2O; (e) EtO2CCH(CHO)2, HCl, EtOH, ZnCl2; (f) Zn,
HOAc.
improved potency both intrinsically and in the cell-based
assay. However, plasma levels of 3 in dogs after oral
administration were 100-fold lower compared to those
for indinavir. The thiomethylpyridine analogue 8 also
showed an improvement in potency relative to indinavir.
However, the plasma concentration of drug in dogs after
oral administration reached a maximum of only 1.16
µM, and no drug could be detected after 8 h. Interest-
ingly, this analogue also had low aqueous solubility (4.5
µg/mL) and a relatively high log P (3.48). It was an early
example of a compound in the HAPA isostere series that
had high lipophilicity and showed some oral bioavail-
ability in dogs.

3390 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Ta ble 3. Bicyclic Heterocycles 26-38
Dorsey et al.
a
b
All entries are for n ) 1 except where noted; data are the mean ( SEM. Solubility determined at pH 7.4 in µg/mL, for L-735,524 (70
µg/mL). c Clog P for indinavir was 2.44, and the measured log P was 2.92. Bioavailability in dogs, each compound was delivered orally
d
in 0.05 M citric acid at 10 mg/kg. For all cases n ) 2 except where noted. Cmax, maximum plasma concentration; C8h, plasma concentration
after 8 h. e Average determination was 29 nM.
The unexpected improvement in the pharmacokinetic
profile of furopyridine 20 (vs indinavir) and the lack of
oral bioavailability observed for the saturated furopy-
ridine 21 required an explanation. Analogue 21 can be
viewed as the cyclic constrained version of 4 (Table 1).
Both 4 and 21 displayed poor pharmacokinetics after
oral dosing in dogs, and each has similar lipophilicities.
Each compound lacks the olefin of the furan ring. The
compounds which do possess good pharmacokinetics, 19,
20, and 22, all belong to the furopyridine class, contain-
ing the furan olefin. The only pharmacokinetic exception
to this group was analogue 23, a compound which does
possess the furopyridine moiety but which lacks oral
bioavailability. It was hypothesized that the olefin of
the furan moiety could be a factor in affecting the
clearance of this class of compounds. To investigate this
hypothesis, several pharmacological experiments were
conducted. First, determination of the time- and dose-
dependent pharmacokinetics of furopryidine 20 in rats,
dogs, and monkeys revealed nonlinear kinetics in each
species.22 The apparent clearance of 20 in these species
decreased with increasing doses, and the apparent half-
life increased with increasing doses. Further investiga-
tion suggested that L-754,394 was acting as a mecha-
nism-based inactivator of two cytochrome P-450 isozymes
(CYP2C and CYP3A) in the liver. This result, when
taken together with pharmacokinetic results illustrated
in Table 2, suggests that the olefin of the furan moiety
is converted into a reactive intermediate, possibly an
epoxide, and is deactivating CYP3A and CYP2C.
L-754,394 satisfied our criteria as a potential backup
candidate to indinavir and was evaluated as a safety
assessment candidate. After high oral dosing in rats and
dogs, toxicity was observed. Further interest in the
development of this compound was precluded because
of this toxicity in combination with nonlinear pharma-
cokinetics.
Undaunted, we continued to examine pyridylmethyl
replacements which would provide a potential drug that
would satisfy the previously established criteria and,
in addition, not inhibit the cytochrome P-450 isozmyes.
The next set of analogues prepared in the furopyridine
series reversed the position of attachment of the bicyclic
heterocycle. The rationale was that a 5,6-heterocycle
bridged to the piperazine moiety through a methylene
linker connected to either the 2- or 3-carbon of the five-
membered ring might shield the reactive olefin and
prevent the CYP isozyme inhibition. The results are
illustrated in Table 3. The isomeric furo[2,3-b]pyridine
26 was prepared, and comparison to L-754,394 revealed
that potency was maintained but the pharmacokinetic
profile changed dramatically. For 26, the concentration

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3391
Ta ble 4. Pharmacokinetic Profile of MK-944a in Animalsa
intravenous administration
oral administration
animal
dose (mg/kg) iv/po
CLp (mL/min/kg)
Vdss (L/kg)
t1/2 (min)
Cmax (µM)
Tmax (min)
F%
rat (n ) 4)
monkey (n ) 2)
dog (n ) 5)
10/20
2/10
2/10
42.3 ( 9.5
13.9
4.4 ( 1.05
1.9 ( 0.8
1.45 ( 0.10
2.61 ( 0.3
47.5 ( 4.5
76.0
53.5 ( 16.9
0.34 ( 0.2
nd
28.3 ( 17.4
42.5 ( 12.6
nd
42.0 ( 16.4
11
nd
68.9 ( 26.9
a
MK-944a was delivered orally in 0.5 M citric acid. CLp, plasma clearance rate; Vdss, volume of distribution; t1/2, plasma half-life; Cmax
,
maximum plasma concentration; Tmax, time of maximum plasma concentration; F%, percent orally bioavailable. F% was determined by
comparing the mean areas under the curves after iv and oral doses. Data are the mean ( SD; nd not detected.
Ta ble 5. Comparative Antiviral Effects of Indinavir and
maximum was 10-fold lower than for L-754,394, and no
compound was detected after 8 h in dog plasma. This
result suggested that the furopyridine moiety of 26 was
not acting as a mechanism-based CYP inhibitor, rein-
forcing our working hypothesis. Two substituted furo-
[2,3-b]pyridine derivatives, 27 and 28, were prepared
but offer no advantage in the pharmacokinetic studies.
Interestingly, the [2,3-c]furopyridine 29 and [3,2-c]-
furopyridine 30 provided maximum drug plasma con-
centrations in dogs of 36 and 34 µM, respectively.
Although these peak plasma levels were high, the lack
of appreciable levels after 8 h indicated a short half-
life and precluded further interest in these analogues.
The thieno[2,3-b]pyridine derivatives 32 and 33 dem-
onstrated good potency, but again no advantages were
seen in their pharmacokinetic profiles. Preparation of
the benzofuran derivative 34 (MK-944a, L-756,423)
revealed a compound with excellent in vitro potency,
IC50 ) 0.18 nM and IC95 ) 29 nM, and also exceptional
pharmacokinetics in dogs. MK-944a has low aqueous
solubility and high lipophilicity. However, after oral
dosing in dogs, it achieved a plasma concentration
maximum of 28 µM, and after 8 h, drug concentrations
of 800 nM were detected. The ratio of concentration of
drug after 8 h in dog plasma to the IC95 value is 27,
which exceeds the criteria previously established. Un-
like indinavir,23 MK-944a did not demonstrate inhibi-
tion of substrates metabolized by CYP3A, CYP2C9,
CYP2D6, and CYP1A2, indicating that it is not a potent
liver microsome inhibitor.24 Several other benzofuran,
benzimidazole, and indole derivatives were prepared,
represented by 35-38, and they provided no advantages
in either potency or pharmacokinetics. In light of the
data generated, it is extremely difficult to draw trends
between lipophilicity, solubility, and pharmacokinetics.
An im a l P h a r m a cok in etic P r ofile of MK-944a .
The pharmacokinetic profile of MK-944a in rats, dogs,
and monkeys is summarized in Table 4. After iv
administration (10 mg/kg) in rats, MK-944a was cleared
rapidly with a large volume of distribution (Vdss). The
half-life (t1/2), although relatively short, was 60% longer
than that of indinavir.6 When MK-944a was given to
rats orally (20 mg/kg) as a solution in 0.05 M citric acid,
it was not well absorbed and the bioavailability (calcu-
lated by comparison between the iv and oral profiles)
was only 11%. No drug (<30 nM) was detected in
plasma of monkeys after a 10 mg/kg dose was given
orally. However, after iv administration (2 mg/kg) in
monkeys, MK-944a had a lower plasma clearance (CLp)
and a longer t1/2 than indinavir by 2.6- and 2.5-fold,
respectively. Although MK-944a and indinavir had
similar bioavailabilities (69% and 72%, respectively) in
dogs, the former had a lower clearance (CLp 4.4 mL/
min/kg) than the latter (CLp 16 mL/min/kg). Therefore,
the area under the curve (AUC) was 3.3-fold greater for
MK-944a in Cell Culturea
IC95 (nM)
assay methodb
indinavir
L-756,423
+10% FBS
50.0
100.0
100.0
200.0
25.0
50.0
25.0
50.0
+50% NHS
+500 µM HSA
+2.0 µg/mL R-GP
a
MT-4 cells were infected with the LAI varient of HVI-1 as
previously described.6
Assays were preformed using culture
b
medium containing one of the following additives: 10% FBS, 10%
fetal bovine serum; 50% NHS, 50% normal human serum; 500 µM
HSA, 500 µM human serum abumin; 2.0 µg/mL R-GP, 2.0 µg/mL
R1 acid glycoprotein.
MK-944a than for indinavir. The Vdss in rats, monkeys,
and dogs was large, suggesting that MK-944a is widely
distributed in animal tissues. Compared to indinavir,
MK-944a possesses a longer half-life and lower clear-
ance in rats, monkeys, and dogs. As an animal species,
dogs were the best predictor of the pharmacokinetic
profile of indinavir in humans (F ) 72% in dogs, F )
∼65% in humans). If dogs are the best predictor of the
pharmacokinetic profile of MK-944a as well, then MK-
944a should demonstrate pharmacokinetic advantages
over indinavir in clinical studies. Therefore, MK-944a
was considered for further development.
P r otein Bin d in g a n d An tivir a l Activity. The
ability of plasma proteins to adversely affect the efficacy
of HIV-1 protease inhibitors has been well docu-
mented.17 The binding of MK-944a to human, dog, and
rat plasma was determined by an ultrafiltration method.6
The unbound fraction of the drug in plasma was
approximately 2.1% for rats, 1% for dogs, and 2.7% for
humans. In the cell-based antiviral assay,6 as illustrated
in Table 5, the addition of a variety of proteins had
minimal effects on potency. The addition of 10% fetal
bovine serum, standard conditions for the assay, re-
sulted in an IC95 determination of 25 nM for MK-944a
and 50 nM for indinavir. The addition of either 50%
normal human serum, 500 µM human serum albumin,
or 2.0 µg/mL of R1 acid glycoprotein resulted in, at most,
a 2-fold reduction in potency for MK-944a. This is in
contrast to the results observed with most other HIV
protease inhibitors which lose between 10- and 100-fold
potency depending on cell type.17 These results demon-
strate that MK-944a is more effective than indinavir
in suppressing the spread of acute HIV-1 infection in
cells in the presence of biologically relavent proteins.
Resista n t Vir u s. The emergence of drug-resistant
mutants has been and will continue to be a critical issue
in the treatment of HIV infection.25 In vivo viral
resistance has been demonstrated for all classes of HIV
inhibitors: the nucleoside and nonnucleoside reverse
transcriptase inhibitors as well as protease inhibitors.26
For protease inhibitors, the appearance of virus with

3392 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Dorsey et al.
Ta ble 6. Resistant Mutant Sequencesa
wild-
type Leu10 Lsy20 Leu24 Met36 Ser37 Met46 Ile54 Arg57 Gln58 Leu63 Ile64 Ala71 Gly73 Val77 Val82 Ile84 Leu90 Ile93
A-44
K-60
V-18
Val
Ile
Ile
Met
Ile
Asp
Asn
Asp
Ile
Ile
Ile
Val
Val
Pro
Pro
Pro
Val
Thr
Ile
Th r
P h e
Glu
Val
Met
Met
Leu
Leu
Ile
Lys
Val
Ser
Leu
a
The wild-type sequence, variant sequence, and patient codes have been defined by Olsen et al.30 and Condra et al.28a The amino acid
residues in bold indicate active site modifications.
Ta ble 7. Comparison of Dissociation Constants (Ki) Obtained
from Inhibition of Wild-Type HIV-1 Protease and Mutant
Enzymes
stones are mainly comprised of indinavir which has
precipitated in the kidneys. The assessment of radi-
olabled indinavir administered to humans and rats has
recently been published.16 In humans, a single oral dose
Ki (nM)
of 400 mg [14C]indinavir was administered, and 11% of
inhibitor
wild-type
A-44
K-60
V-18
unchanged indinavir was recovered in the urine. Bile-
cannulated, fasted male Sprague-Dawley rats were
dosed intravenously (10 mg/kg [14C]indinavir), and urine
was collected over a 4-h period. Analysis determined
that 9.4% of unchanged drug was eliminated in the
urine. In contrast, when MK-944a was administered to
rats (10 mg/kg iv) no parent drug could be detected in
the urine. These data would suggest that MK-944a
might provide a lower incidence of nephrolithiasis in
patients. Clinical studies will be required to answer this
hypothesis.
MK-944a
indinavir
saquinavir
ritonavir
nelfinavir
0.049
0.24
0.062
0.062
0.14
8
15
15
60
16
20
50
3.7
40
33
25
40
117
23
27
reduced susceptibility has occurred both in cell culture
experiments27 and in human clinical trials.13,28 The use
of suboptimal doses of indinavir (monothearpy) in initial
clinical trials resulted in a lowering of viral load.
However, over time mutant variants that exhibited
resistance to indinavir began to emerge, and several of
these have been characterized both phenotypically and
genotypically.28a Not only was resistance to indinavir
observed but also cross-resistance to a structurally
diverse group of protease inhibitors. Also, researchers28c,29
have reported that, in patients treated with other
protease inhibitors, cross-resistant variants have de-
veloped.
Table 6 illustrates three high-level, cross-resistant
mutant sequences originally identified by Condra et
al.13,28a and the specific sites of mutation. Each variant
has one specific active site mutation that is supported
by 8-10 nonactive site mutations. Interestingly, the
nonactive site amino acid substitutions have been
estimated to account for 40-65% of the loss in inhibition
binding energy.30 Therefore, these nonactive site changes
also contribute significantly to the issue of cross-
resistance.
A comparison of dissociation constants between sev-
eral Food and Drug Administration approved HIV-1
protease inhibitors and MK-944a versus selected high-
level mutant proteases is illustrated in Table 7. All five
compounds exhibit subnanomolar potency against the
wild-type protease. However, each compound experi-
ences a 60-1800-fold loss in potency against the mutant
proteases (A-44, K-60, and V-18). MK-944a is slightly
more active against the A-44 and K-60 strains than the
other protease inhibitors and is equipotent to ritonavir
and nelfinavir against the V-18 strain. However, for
MK-944a each mutant viral protease increases the Ki
to 163 and 510 times the wild-type Ki value of 0.049
nM, indicating significant resistance. In light of the
previous investigations focused on the resistance issue,
and the structural similarity to indinavir, it is not
surprising that this HIV-1 protease inhibitor has a
similar resistance profile. The inherent increase in
potency for MK-944a against the wild-type enzyme and
potential ease of dosing should translate into a de-
creased chance of development of resistance.
Con clu sion
In summary, the modification of our HAPA transition-
state isosteres has provided several compounds that
exceeded our selection criteria for a backup candidate
to indinavir. The first compound identified, L-754,394,
was a potent CYP3A inhibitor, and this resulted in an
extraordinary pharmacokinetic profile in animals. How-
ever, safety issues prevented the development of
L-754,394 and the elimination of CYP3A inhibition
became an additional criterion. By continuing to modify
the physical properties of this series (i.e. solubility and
lipophilicity) and maintaining potency, MK-944a was
identified.
In vitro results demonstrate that MK-944a is potent
and competitively inhibits HIV-1 PR with a Ki value of
0.049 nM. Cell culture assays demonstrate that the
compound is slightly more effective than indinavir in
suppressing the spread of acute HIV-1 infection. More
importantly, the addition of up to 50% human serum
or R1 acid glycoprotein in the viral assay minimally
affects the potency of MK-944a (25-50 nM). At 10 µM,
the compound did not significantly inhibit a variety of
other proteinases including human cathepsin D, porcine
pepsin, and human gastric and bovine chymosin. MK-
944a is not a competitive inhibitor for any of the major
cytochrome P-450 isozymes tested. Also, low renal
excretion of MK-944a suggests that nephrolithiasis may
not be an issue in humans. Finally, no serious safety
liabilities have been observed in several animal experi-
ments.
Resistance to HIV-1 PR inhibitors currently plays a
significant role in effective, long-term antiviral therapy.
Viral replication under selective pressure drives the
evolution of resistance, whereas potent inhibition of
viral growth delays viral resistance. Therefore, to avoid
resistance in a clinical setting, one should design a drug
that has several characteristics. First, the compound
should be potent in a cell-based assay and in the
presence of biologically relevant proteins, and when
Nep h r olith ia sis. Clinical nephrolithiasis is a dose-
limiting side effect associated with indinavir.12 The

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3393
129.5, 129.8 (2C), 136.2, 140.3, 140.5, 140.6, 148.0, 151.9,
169.3, 175.0. Anal. (C40H49N5O4) C, H, N.
orally administered to humans it should maintain
significantly higher plasma concentrations then its cell-
based IC95 value. If this can be achieved, this should
completely restrict replication and, therefore, severely
limit the chance of mutation selection. Second, a poten-
tial drug should have easy dosing requirements and
have minimal side effects. The result would be an
increase in patient compliance and, therefore, reduce
the chances of the patient being exposed to suboptimal
plasma concentrations of drug during antiviral therapy.
The preclinical data suggest that MK-944a has the
potential of having these characteristics, in humans,
and is being pursued in humans clinical trials. Ad-
vanced human clinical trials with MK-944a, exploring
once or twice a day dosing in combination with indi-
navir, have been ongoing, and those results will be
presented when available.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(3-(6-eth oxyp yr id yl)m eth yl)-2(S)-N′-(ter t-
bu tylcar boxam ido)piper azin yl))pen tan am ide (4). Meth od
B: Preparation of 3-chloromethyl-6-ethoxypyridine followed
a four-step sequence. Step 1: To a solution of ethyl 6-chlo-
ronicotinate (2.38 g, 12.85 mmol) in ethanol (120 mL) was
added portionwise sodium hydride (1.56 g, 38.56 mmol) over
20 min. After 16 h of reflux, the mixture was cooled to room
temperature and quenched with aqueous saturated NH4Cl (30
mL) and concentrated. The residue was partitioned between
EtOAc and water and extracted with EtOAc (3 × 30 mL). The
combined organic layer was washed with water (1 × 50 mL),
brine (1 × 75 mL), dried over MgSO4, filtered, and concen-
trated. The residue was purified via column chromatography
[50- × 150-mm column, gradient elution Hex:EtOAc, 9:1 (1 L)
to 4:1 (1 L)] to provide 1.95 g (77% yield) of ethyl 6-ethoxyni-
cotinate as a clear oil: TLC (Hex:EtOAc, 4:1) Rf ) 0.68; 1H
NMR (400 MHz, CDCl3) δ 1.35-1.42 (m, 6H), 4.33-4.45 (m,
4H), 6.73 (d, J ) 8.8 Hz, 1H), 8.14 (d, J ) 8.8 Hz, 1H), 8.82 (s,
1H). Step 2: To a solution of ethyl 6-ethoxynicotinate (0.864
g, 4.43 mmol) in THF (12 mL) cooled to 0 °C was added
DIBAL-H (1 M in Hex, 13.2 mL, 13.28 mmol) slowly. After 1
h Rochelle’s salt (44 mL) was added and the mixture was
stirred for 18 h. The solvent was removed in vacuo and the
residue was dissolved in EtOAc (100 mL) and washed with
saturated NaHCO3 (1 × 30 mL), water (1 × 50 mL), brine (1
× 75 mL), dried over MgSO4 and concentrated. The residue
was purified via column chromatography [30- × 150-mm
column, gradient elution Hex:EtOAc, 4:1 (1 L) to 3:1 (1 L)].
This provided 0.622 g (91% yield) of 6-ethoxy-3-hydroxyl-
methylpyridine as a pale yellow oil: TLC (Hex:EtOAc, 4:1) Rf
Exp er im en ta l Section
Biologica l Meth od s. Protease inhibition assays,30 acute
infection assays, and animal pharmacokinetic studies have
been previously described.6
Ch em ica l Meth od s. Reactions were carried out in an argon
atmosphere, using solvents and reagents from commercial
suppliers which were used as received. All reactions were
monitored by thin-layer chromatography (TLC) using E. Merck
silica gel 60 F254 plates (0.25-mm thickness). Flash column
chromatography was performed with solvents indicated using
E. Merck silica gel 60 (230-400 mesh). All melting points were
obtained on a Thomas-Hoover apparatus and were uncor-
rected. Optical rotations were recorded on a Perkin-Elmer 241
polarimeter. Proton magnetic resonance spectra were obtained
on either a Varian XL-300 (300 MHz) or a Varian VXR-400
(400 MHz) spectrometer using TMS as an internal standard.
The abbreviations AcOH, DIBAL-H, DME, DMF, EDC, EtOAc,
Hex, HCl, HOBt, MeOH, NaB(OAc)3H, and THF refer to acetic
acid, diisobutylaluminum hydride, 1,2-dimethoxyethane, N,N-
dimethylformamide, 1-ethyl-3-(3-(dimethylamino)propyl)car-
bodiimide hydrochloride, ethyl acetate, n-hexanes, hydrochloric
acid, 1-hydroxybenzotriazole hydrate, sodium triacetoxyboro-
hydride, and tetrahydrofuran, respectively.
1
) 0.2; H NMR (400 MHz, CDCl3) δ 1.38 (t, J ) 7.1 Hz, 3H),
2.76 (br s, 1H), 4.31 (q, J ) 7.1 Hz, 2H), 4.57 (s, 2H), 6.70 (d,
J ) 8.4 Hz, 1H), 7.58 (dd, J ) 8.4, 2.2 Hz, 1H), 8.03 (d, J )
2.2 Hz, 1H). St ep 3: To a solution of 6-ethoxy-3-hydroxyl-
methylpyridine (0.924 g, 6.03 mmol) in CH2Cl2 was added
thionyl chloride (2.5 mL, 34.2 mmol). After 3 h the solvent was
removed in vacuo to provide 0.527 g of 3-chloromethyl-6-
ethoxypyridine hydrochloride as a tan solid which was used
directly in the next step: 1H NMR (400 MHz, CDCl3) δ 1.55
(t, J ) 6.9 Hz, 3H), 4.59 (s, 2H), 4.73 (q, J ) 6.9 Hz, 2H), 7.14
(d, J ) 9.0 Hz, 1H), 8.13 (dd, J ) 9.0, 2.2 Hz, 1H), 8.39 (d, J
) 2.0 Hz, 1H). Step 4: To a solution of amine 2 (0.40 g, 0.765
mmol) dissolved in 5 mL of DMF were added 3-chloromethyl-
6-ethoxypyridine hydrochloride (0.191 g, 0.918 mmol) and
triethylamine (0.30 mL, 2.14 mmol). After 48 h the solvent
was removed in vacuo and the residue was dissolved in EtOAc
(100 mL) and washed with water (6 × 30 mL), brine (1 × 30
mL), dried over MgSO4 and concentrated. The residue was
purified via column chromatography [30- × 150-mm column,
gradient elution CH2Cl2:CHCl3 saturated with NH3:MeOH, 1%
(1 L), 1.5% (1 L), 2% (1 L)]. This provided 0.387 g (77% yield)
of a white foam which could be further purified by triturating
with EtOAc and Hex: mp 88-93 °C; TLC (MeOH:CHCl3
P r ep a r a tion of N-(2(R)-Hyd r oxy-1(S)-in d a n yl)-2(R)-
p h en ylm eth yl-4(S)-h yd r oxy-5-(1-(4-(3-qu in olin ylm eth yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e (3). Meth od A: To a solution of N-(2(R)-hydroxy-1(S)-
indanyl)-2(R)-phenylmethyl-4(S)-hydroxy-5-(1-(2(S)-N-(tert-bu-
tylcarboxamido)piperazinyl))pentanamide (2) (0.40 g, 0.765
mmol) dissolved in 5 mL of dichloroethane were added
3-quinolinecarboxaldehyde (0.144 g, 0.916 mmol), AcOH (0.54
mL, 0.916 mmol) and then Na(OAc)3H (0.344 g, 1.53 mmol).
After 48 h the solvent was removed in vacuo and the residue
was dissolved in EtOAc (100 mL) and washed with saturated
NaHCO3 (1 × 30 mL), water (1 × 50 mL), brine (1 × 75 mL),
dried over MgSO4 and concentrated. The residue was purified
via column chromatography [30- × 150-mm column, gradient
elution CH2Cl2:CHCl3 saturated with NH3:MeOH 1% (1 L), 2%
(1.5 L), 3% (0.5 L)]. This provided 0.335 g (66% yield) of a white
foam which could be further purified by triturating with EtOAc
and Hex: mp 168-170 °C; TLC (MeOH:CHCl3 saturated with
saturated with NH3:CH2Cl2, 5:30:65) Rf ) 0.5; [R]22 +2.38 (c
D
) 1.00, CHCl3); 1H NMR (400 MHz, CDCl3) δ 1.35 (s, 9H), 1.39
(t, J ) 7.0 Hz, 3 H), 1.54-1.58 (m, 1H), 1.91-1.97 (m, 1H),
2.26-2.32 (m, 1H), 2.48-2.53 (m, 2H), 2.64-3.05 (m, 9H), 3.17
(br s, 1H), 3.40 (s, 2H), 3.61-3.67 (m, 1H), 3.78-3.81 (m, 2H),
4.27 (d, J ) 4.4 Hz, 1H), 4.35 (q, J ) 7.1 Hz, 2H), 5.28 (dd, J
) 8.6, 4.9 Hz, 1H), 5.89 (d, J ) 8.4 Hz, 1H), 6.70 (d, J ) 8.4
Hz, 1H), 7.09-7.32 (m, 10 H), 7.47 (dd, J ) 8.5, 2.3 Hz, 1H),
7.88 (br s, 1H), 8.01 (d, J ) 2.3 Hz, 1H); 13C NMR (75 MHz,
CDCl3) δ 14.6, 29.1 (3C), 38.1, 39.0, 39.6, 46.9, 51.1, 52.6, 54.3,
57.5, 59.6, 61.3, 61.8, 63.8, 65.6, 73.0, 110.9, 123.8, 124.6, 125.2,
126.5, 126.8, 128.0, 128.5 (2C), 129.1 (2C), 139.7, 140.0, 140.3,
140.4, 147.4, 155.6, 163.6, 169.1, 174.8. Anal. (C38H51N5O4‚
1.0H2O) C, H, N.
NH3:CH2Cl2, 5:30:65) Rf ) 0.5; [R]22 +1.36 (c ) 1.00, CHCl3);
D
1H NMR (400 MHz, CDCl3) δ 1.06 (d, J ) 3.7 Hz, 1H), 1.36 (s,
9H), 1.55-1.57 (m, 1H), 1.92-1.96 (m, 1H), 2.36-2.40 (m, 1H),
2.52 (dd, J ) 13.4, 2.8 Hz, 1H) 2.59-2.93 (m, 10H), 2.98-3.04
(m, 1H), 3.18-3.19 (m, 1H), 3.64 (d, J ) 13.0 Hz, 1H), 3.71 (d,
J ) 13.0 Hz, 1H), 3.78-3.83 (m, 2H), 4.25-4.26 (m, 1H), 5.26
(dd, J ) 8.5, 4.9 Hz, 1H), 5.88 (d, J ) 8.8 Hz, 1H), 7.08-7.31
(m, 9H), 7.54-7.58 (m, 1H), 7.70-7.73 (m, 1H), 7.78-7.80 (m,
2H), 8.01 (s, 1H), 8.11 (d, J ) 8.4 Hz, 1H), 8.85 (s, 1H); 13C
NMR (100 MHz, CDCl3) δ 29.3 (3C), 38.3, 39.3, 39.9, 47.1, 47.8,
51.4, 53.0, 55.0, 57.7, 60.8, 61.6, 64.2, 66.0, 73.2, 124.1, 125.4,
126.7, 127.0, 127.3, 127.7, 127.9, 128.2, 128.7 (2C), 129.3 (2C),
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(3-(6-m eth ylpyr id yl)m eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (5). Start-
ing from methyl 6-methylnicotinate and following method B

3394 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Dorsey et al.
steps 2-4 the title compound was prepared: mp 186-188 °C;
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 5:30:65) Rf
°C for 3 h. The thick slurry was cooled to 120 °C, diluted with
toluene and filtered through Celite. The filtrate was concen-
trated and the residue was purified via column chromatogra-
phy [40- × 150-mm column, gradient elution Hex:EtOAc, 4:1
(1 L) to 3:1 (1 L)] to provide 0.70 g (33% yield) of ethyl
4-chlorofuro[2,3-b]pyridine-5-carboxylate as a white solid: TLC
(Hex:EtOAc, 2:1) Rf ) 0.41; 1H NMR (400 MHz, CDCl3) δ 1.44
(t, J ) 7.2 Hz, 3H), 4.46 (q, J ) 7.2 Hz, 2H), 6.98 (d, J ) 2.4
Hz, 1H), 7.78 (d, J ) 2.5 Hz, 1H), 8.88 (s, 1H). Following the
procedure outlined in method B, steps 2-4 then provided the
) 0.34; [R]22 +2.82 (c ) 1.00, CHCl3); 1H NMR (400 MHz,
D
CDCl3) δ 1.09 (d, J ) 3.8 Hz, 1H), 1.35 (s, 9H), 1.56-1.59 (m,
1H), 1.92-1.97 (m, 1H), 2.27-2.33 (m, 1H), 2.49-2.54 (m, 1H),
2.56 (s, 3H), 2.61-2.69 (m, 2H), 2.72-3.05 (m, 9H), 3.17 (t, J
) 3.4 Hz, 1H), 3.43 (d, J ) 13.0 Hz, 1H), 3.49 (d, J ) 13.0 Hz,
1H), 3.77-3.80 (m, 2H), 4.27 (m, 1H), 5.28 (dd, J ) 8.4, 4.8
Hz, 1H), 5.90 (d, J ) 8.6 Hz, 1H), 7.11-7.32 (m, 10H), 7.47
(dd, J ) 7.9, 2.2 Hz, 1H), 7.84 (br s, 1H), 8.40 (d, J ) 1.6 Hz,
1H); 13C NMR (75 MHz, CDCl3) δ 24.1, 29.0 (3C), 38.0, 39.1,
39.6, 46.7, 47.5, 51.1, 52.6, 54.6, 57.4, 59.9, 61.3, 63.9, 65.6,
72.9, 123.0, 123.9, 125.1, 126.4, 126.7, 127.9, 128.5 (2C), 129.0
(2C), 129.1, 137.2, 140.0, 140.4 (2C), 149.8, 157.9, 169.2, 174.9;
HRMS (FAB-POSI; M + 1) calcd 628.3857, found 628.3839.
Anal. (C37H49N5O4) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(3-(6-ch lor op yr id yl)m eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (6). Start-
ing with methyl 6-chloronicotinate and following method B
steps 2-4 the title compound was prepared: mp 168-170 °C;
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf
) 0.48; 1H NMR (300 MHz, CDCl3) δ 1.35 (s, 9H), 1.55 (m,
1H), 1.97 (m, 1H), 2.31-2.39 (m, 1H), 2.55-2.72 (m, 7H), 2.74-
3.05 (m, 5H), 3.15 (s, 1H), 3.42-3.53 (m, 2H), 3.81 (br s, 2H),
4.25 (d, J ) 3.9 Hz, 1H), 5.27 (dd, J ) 8.2, 4.8 Hz, 1H), 6.05
(d, J ) 8.4 Hz, 1H), 7.12-7.33 (m, 11 H), 7.51 (br s, 1H), 7.57-
7.60 (m, 1H), 8.29 (s, 1H). Anal. (C36H46N5O4Cl‚0.55H2O) C,
H, N.
title compound 19: mp 174-176 °C; [R]22 +1.82 (c ) 1.00,
D
CHCl3); 1H NMR (400 MHz, CDCl3) δ 1.30 (s, 9H), 1.54-1.58
(m, 1H), 1.84-2.06 (m, 3H), 2.44-3.04 (m, 13 H), 3.13 (t, J )
3.5 Hz, 1H), 3.70 (s, 2H), 3.79-3.85 (m, 1H), 4.27 (dd, J ) 4.9,
3.9 Hz, 1H), 5.26 (dd, J ) 8.6, 4.9 Hz, 1H), 6.0.37-6.40 (m,
1H), 6.88 (d, J ) 2.5 Hz, 1H), 7.11-7.31 (m, 9 H), 7.56 (br s,
1H), 7.75 (d, J ) 2.5 Hz, 1H), 8.26 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 29.2, 38.3, 39.3, 39.9, 47.0, 47.7, 51.4, 53.0, 54.7, 56.9,
57.7, 61.5, 61.8, 64.3, 65.9, 73.2, 105.0, 119.6, 124.1, 125.4,
126.2, 126.7, 127.0, 128.2, 128.7, 129.3, 137.7, 140.2, 140.6,
146.0, 146.6, 161.7, 169.3, 175.1; MS (FAB-POSI) m/z 688 (M
+ 1). Anal. (C38H46N5O4Cl) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(5-fu r o[2,3-b]pyr idylm eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (20). From
5-(chloromethyl)furo[2,3-b]pyridine19 and amine 2 and follow-
ing the procedure outlined in method B, step 4, the title
compound was prepared as a white solid in 84% yield: mp
184-185 °C; [R]22 +2.96 (c ) 1.00, CHCl3); 1H NMR (400
D
MHz, CDCl3) δ 1.35 (s, 9H), 1.58-1.61 (m, 1H), 1.93-1.99 (m,
1H), 2.34-2.38 (m, 1H), 2.53-2.62 (m, 4H), 2.74-3.09 (m, 9H),
3.15 (d, J ) 3.3 Hz, 1H), 3.59 (s, 2H), 3.80 (s, 2H), 4.26 (d, J
) 4.2 Hz, 1H), 5.27 (dd, J ) 8.4, and 4.9 Hz, 1H), 5.96 (d, J )
8.4 Hz, 1H), 6.76 (dd, J ) 2.6, 0.7 Hz, 1H), 7.10-7.32 (m, 10H),
7.73 (d, J ) 2.6 Hz, 1H), 7.85 (d, J ) 2.0 Hz, 1H), 8.25 (d, J )
2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 29.3 (3C), 38.3, 39.3,
39.9, 47.1, 47.8, 51.4, 52.9, 54.7, 57.7, 60.4, 61.6, 64.3, 65.9,
73.2, 105.9, 119.4, 124.1, 125.4, 126.7, 127.0, 128.2, 128.3,
128.7 (2C), 129.3 (2C), 131.1, 140.2, 140.5, 140.6, 145.4, 145.8,
162.0, 169.4, 175.0. Anal. (C38H47N5O5‚0.25H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(3-(2-m et h oxyp yr id yl)m et h yl)-2(S)-N′-
(ter t-b u t ylca r b oxa m id o)p ip er a zin yl))p en t a n a m id e (7).
Methyl 2-methoxynicotinate was prepared from the com-
mercially available acid and (trimethylsilyl)diazomethane in
methanol and chloroform. 2-Methoxy-3-chloromethylpyridine
was prepared from methyl 2-methoxynicotinate following
method B, steps 2 and 3. The title compound 7 was prepared
using amine 2 and following method B, step 4: mp 81-85 °C;
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 5:30:65) Rf
1
) 0.38; H NMR (300 MHz, CDCl3) δ 1.29 (s, 9H), 1.51-1.59
(m, 1H), 1.76 (br s, 2H), 1.92-1.98 (m, 1H), 2.32-2.39 (m, 1H),
2.47-3.04 (m, 12H), 3.14 (d, J ) 3.2 Hz, 1H), 3.44-3.47 (m,
2H), 3.78-3.82 (m, 1H), 3.91-3.95 (m, 1H), 3.94 (s, 3H), 4.26
(t, J ) 4.3 Hz, 1H), 5.24-5.29 (m, 1H), 6.03 (d, J ) 8.6 Hz,
1H), 6.86 (dd J ) 7.1, 5.0 Hz, 1H), 7.11-7.31 (m, 9H), 7.48
(dd, J ) 7.1, 1.8 Hz, 1H), 7.97 (br s, 1H), 8.11 (dd, J ) 5.0, 1.8
Hz, 1H); HRMS (FAB-POSI; M + 1) calcd 644.3811, found
644.3817. Anal. (C37H49N5O4‚0.95H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h y d r o x y -5-(1-(4-(5-(2,3-d ih y d r o fu r o [2,3-b ]p y r id y l)-
m et h yl)-2(S)-N′-(ter t-b u t ylca r b oxa m id o)p ip er a zin yl))-
p en ta n a m id e (21). To a solution of 20 (0.5 g, 0.764 mmol)
dissolved in THF (30 mL) and water (6 mL) were added
ammonium formate (0.237 g, 3.82 mmol) and 5% Pd/C (0.7 g).
After 1.5 h of reflux, the cooled mixture was filtered through
a plug of Celite and washed with EtOAc (300 mL). Evaporation
of volatiles provided a residue which was purified via column
chromatography [25- × 150-mm column, gradient elution, CH2-
Cl2:CHCl3 saturated with NH3:MeOH 1% (1 L), 2% (1 L), 5%
(1 L)]. The resulting solid was triturated with EtOAc and Hex
to afford 0.23 g (46% yield) of the title compound as a white
solid: mp 203-204 °C; TLC (MeOH:CHCl3 saturated with
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(3-(2-th iom eth ylp yr id yl)m eth yl)-2(S)-N′-
(ter t-bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (8).
Methyl 2-(methylthio)nicotinate was prepared from the com-
mercially available acid and (trimethylsilyl)diazomethane in
methanol and chloroform. 2-Methylthio-3-chloromethylpyri-
dine was prepared from methyl 2-(methylthio)nicotinate fol-
lowing method B, steps 2 and 3. Compound 8 was prepared
using amine 2 and following method B, step 4: mp 85-93 °C;
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 5:30:65) Rf
1
NH3:CH2Cl2, 10:30:60) Rf ) 0.37; H NMR (400 MHz, CDCl3)
δ 1.35 (s, 9H), 1.45 (br s, 1H), 1.52-1.60 (m, 1H), 1.90 (br s,
1H), 1.92-1.99 (m, 1H), 2.27-2.36 (m, 1H), 2.48-3.08 (m,
10H), 3.12 (br s, 1H), 3.23 (t, J ) 8.6 Hz, 2H), 3.38 (s, 2H),
3.77-3.83 (m, 1H), 3.95 (br s, 1H), 4.27 (br s, 1H), 4.63 (t, J )
8.6 Hz, 2H), 5.27 (dd, J ) 8.6, 4.9 Hz, 1H), 6.11-6.19 (m, 1H),
7.09-7.10 (m, 2H), 7.16-7.17 (m, 2H), 7.23-7.32 (m, 6H), 7.40
(s, 1H), 7.78 (br s, 1H), 7.84 (s, 1H); MS (FAB-POSI) m/z 656
(M + 1). Anal. (C38H49N5O5) C, H, N.
1
) 0.39; H NMR (300 MHz, CDCl3) δ 1.30 (s, 9H), 1.54-1.64
(m, 1H), 1.68 (br s, 2H), 1.92-2.0 (m, 1H), 2.38-2.43 (m, 1H),
2.56 (s, 3H), 2.51-3.02 (m, 11 H), 3.17 (br s, 1H), 3.43 (d, J )
13.7 Hz, 1H), 3.51 (d, J ) 13.7 Hz, 1H), 3.79-3.83 (m, 2H),
4.28 (br s, 1H), 5.27-5.29 (m, 1H), 5.99 (d, J ) 8.4 Hz, 1H),
6.99 (dd, J ) 7.3, 4.9 Hz, 1H), 7.13-7.33 (m, 9H), 7.42 (d, J )
7.5 Hz, 1H), 7.50 (br s, 1H), 8.41 (dd, J ) 4.8, 1.6 Hz, 1H); MS
(FAB-POSI) m/z 660 (M + 1). Anal. (C37H49N5O4S‚0.45H2O)
C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(6-fu r o[3,2-b]pyr idylm eth yl)-2(S)-N′-(ter t-
b u t ylca r b oxa m id o)p ip er a zin yl))p en t a n a m id e (22). 6-
(Ch lor om eth yl)fu r o[3,2-b]pyr idin e (13). A solution of 3-tert-
butyloxycarbonylaminofuran (12) (3.47 g, 18.94 mmol) in
ethanol (25 mL) was treated with concentrated HCl (25 mL)
and zinc chloride in ether (1.0 M, 20.8 mL). After 5 min,
ethoxycarbonylmalonaldehyde20 (3.0 g, 20.8 mmol) dissolved
in ethanol (15 mL) was added to the green solution. After
warming for 2 h at 80 °C, the mixture was cooled and the
volatiles were removed in vacuo. The residue was dissolved
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(5-(4-ch lor ofu r o[2,3-b]p yr id yl)m et h yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e (19). 4-Ch lor o-5-(ch lor om et h yl)fu r o[2,3-b]p yr i-
d in e (11). A solution of 4-chlorofuro[2,3-b]-2,5-dicarboxylic
acid 5-ethyl ester (10)19 (2.51 g, 9.3 mmol) in quinoline (4 mL)
was treated with copper(I) oxide (0.251 g) and heated to 150

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3395
in CH2Cl2 and washed with NaOH (1 × 50 mL, 5 N) and water
(1 × 50 mL), dried over MgSO4, filtered, and concentrated to
a brown oil. The residue was purified via column chromatog-
raphy [40- × 150-mm column, gradient elution Hex:EtOAc,
3:2 (1 L) to 1:1 (1 L)] to provide 0.447 g (12% yield) of an orange
m et h yl)-2(S)-N′-(ter t-b u t ylca r b oxa m id o)p ip er a zin yl))-
pen tan am ide (24).6-(Ch lor om eth yl)-5,7-dim eth ylpyr azolo-
[3,4-b]pyr idin e (16) To a solution of ethyl 4-chloro-5,7-dimeth-
ylpyrazolo[3,4-b]pyridine-3-carboxylate (0.502 g, 1.98 mmol)
in AcOH (6 mL) was added zinc powder (0.259 g, 3.96 mmol).
The mixture was warmed to 100 °C for 5 h, filtered (hot)
through a plug of Celite and washed with AcOH (70 mL). The
volatiles were removed in vacuo and the remaining oil was
partitioned between CH2Cl2 (50 mL) and aqueous saturated
Na2CO3 (50 mL). The aqueous was extracted with CH2Cl2 (2
× 50 mL) and the combined organic layer was washed with
water (1 × 30 mL) and brine (1 × 30 mL), dried over MgSO4,
filtered and concentrated to a white solid (0.29 g, 67% yield):
1H NMR (400 MHz, CDCl3) δ 1.44 (t, J ) 7.1 Hz, 3H), 2.61 (s,
3H), 4.12 (s, 3H), 4.45 (q, J ) 7.1 Hz, 2H), 8.66 (d, J ) 2.0 Hz,
1H), 9.15 (d, J ) 2.0 Hz, 1H). Following method B, steps 2-4,
compound 25 was prepared in 64% yield as a white solid: mp
163-168 °C; TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2,
5:30:65) Rf ) 0.37; 1H NMR (400 MHz, CDCl3) δ 1.36 (s, 9H),
1.55-1.62 (m, 3H), 1.92-1.98 (m, 1H), 2.31-2.36 (m, 1H),
2.51-3.01 (m, 10H), 2.56 (s, 3H), 3.19 (s, 1H), 3.59 (d, J )
12.8 Hz, 1H), 3.63 (d, J ) 12.8 Hz, 1H), 3.78 (br s, 2H), 4.09
(s, 3H), 4.23-4.26 (m, 1H), 5.28 (dd, J ) 8.6, 4.9 Hz, 1H), 5.89
(d, J ) 8.6 Hz, 1H), 7.09-7.33 (m, 11H), 7.86 (s, 1H), 8.43 (s,
1H). Anal. (C39H51N7O4‚0.1H2O) C, H, N.
1
solid: TLC (Hex:EtOAc, 1:2) Rf ) 0.44; H NMR (400 MHz,
CDCl3) δ 1.43 (t, J ) 7.1 Hz, 3H), 4.44 (q, J ) 7.1 Hz, 2H),
7.05 (dd, J ) 2.2, 1.1 Hz, 1H), 8.00 (d, J ) 2.2 Hz, 1H), 8.37
(dd, J ) 2.2, 1.1 Hz, 1H), 9.02 (d, J ) 1.7 Hz, 1H). Following
the procedure outlined in method B, steps 2-4 then provided
the title compound 22 as a white solid: mp 160-161 °C; [R]22
D
+1.92 (c ) 1.00, CHCl3); 1H NMR (400 MHz, CDCl3) δ 1.35 (s,
9H), 1.52-1.58 (m, 1H), 1.93-2.01 (m, 1H), 1.96-2.16 (br s,
2H), 2.38-2.42 (m, 1H), 2.51-2.99 (m, 11 H), 3.10 (t, J ) 3.5
Hz, 1H), 3.61 (s, 2H), 3.79-3.85 (m, 1H), 4.22-4.29 (m, 1H),
5.26 (dd, J ) 8.5, 4.9 Hz, 1H), 6.33 (d, J ) 8.5 Hz, 1H), 6.98
(dd, J ) 2.3, 0.9 Hz, 1H), 7.10-7.30 (m, 10 H), 7.65 (br s, 1H),
7.71 (s, 1H), 7.86 (d, J ) 2.2 Hz, 1H), 8.46 (d, J ) 1.5 Hz, 1H);
13C NMR (75 MHz, CDCl3) δ 29.0 (3C), 38.1, 39.0, 39.6, 46.8,
47.6, 51.2, 52.7, 54.5, 57.4, 60.4, 61.3, 64.0, 65.7, 73.0, 108.1,
118.9, 123.8, 125.1, 126.5, 126.8, 127.9, 128.2, 128.5 (2C), 129.0
(2C), 140.0, 140.3, 140.4, 147.1, 147.2, 147.6, 149.3, 169.1,
174.8; HRMS (FAB-POSI; M + 1) calcd 654.3655, found
654.3644. Anal. (C38H47N5O5‚0.45H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(6-fu r o[2,3-b]p yr id ylca r b on yl)-2(S)-N′-
(ter t-bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (23).
F u r o[2,3-b]p yr id in e-5-ca r boxylic Acid . A solution of LiOH
monohydrate (0.208 g, 8.72 mmol) in water (10 mL) was added
to a solution of ethyl furo[2,3-b]pyridine-5-carboxylate19 (0.55
g, 2.91 mmol) and THF (10 mL). After 1 h the volatiles were
removed in vacuo; the aqueous was acidified to pH 3 with 10%
HCl, and the resulting solid was isolated by filtration. This
solid was dried in vacuo at 50 °C to yield 0.433 g (91%) as a
white solid: 1H NMR (400 MHz, DMSO-d6) δ 7.15 (d, J ) 2.3
Hz, 1H), 8.25 (d, J ) 2.3 Hz, 1H), 8.68 (d, J ) 1.9 Hz, 1H),
8.88 (d, J ) 1.9 Hz, 1H). A solution of furo[2,3-b]pyridine-5-
carboxylic acid (0.112 g, 0.689 mmol) in DMF (2.0 mL) was
treated with amine 2 (0.30 g, 0.575 mmol), EDC hydrochloride
(0.132 g, 0.689 mmol), HOBt (0.093 g, 0.689 mmol) and then
triethylamine (0.192 mL, 1.38 mmol). After 24 h the mixture
was diluted with EtOAc (100 mL) and washed with aqueous
saturated NaHCO3 (1 × 5 mL), water (4 × 5 mL) and brine (1
× 5 mL), and dried over MgSO4, filtered, and concentrated to
an oil. The residue was purified via column chromatography
[20- × 150-mm column, gradient elution, CH2Cl2:CHCl3 satu-
rated with NH3:MeOH, 1% (0.5 L), 2% (0.5 L), 3% (0.5 L)].
The resulting solid was triturated with EtOAc and Hex to
afford 0.28 g (73% yield) of the title compound as a white
solid: mp 114-124 °C; TLC (MeOH:CHCl3 saturated with
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(2-fu r o[2,3-b]pyr idylm eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (26). Fol-
lowing method A and using 2-formylfuro[2,3-b]pyridine31 and
amine 2 compound 26 was prepared as a white solid in 72%
yield: mp 92-96 °C; TLC (MeOH:CHCl3 saturated with NH3:
CH2Cl2, 5:30:65) Rf ) 0.37; 1H NMR (400 MHz, CDCl3) δ 1.36
(s, 9H), 1.54-1.62 (m, 1H), 1.90-1.96 (m, 1H), 2.18 (br s, 2H),
2.40-3.02 (m, 12 H), 3.13 (br s, 1H), 3.62 (d, J ) 14.2 Hz, 1H),
3.71 (d, J ) 14.2 Hz, 1H), 3.76-3.81 (m, 1H), 4.04 (br s, 1H),
4.27 (br s, 1H), 5.27 (dd, J ) 8.5, and 4.8 Hz, 1H), 6.23 (br s,
1H), 6.61 (s, 1H), 7.06-7.29 (m, 10H), 7.86 (dd, J ) 7.6, 1.6
Hz, 1H), 8.05 (br s, 1H), 8.28 (dd, J ) 4.9, 1.6 Hz, 1H); HRMS
(FAB-POSI; M + 1) calcd 654.3655, found 654.3649. Anal.
(C38H47N5O5‚0.5H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(2-(5-eth ylcar boxylate fu r o[2,3-b]pyr idyl)-
m et h yl)-2(S)-N′-(ter t-b u t ylca r b oxa m id o)p ip er a zin yl))-
p en ta n a m id e (27). Eth yl 2-Hyd r oxym eth ylfu r o[2,3-
b]pyr idin e-5-car boxylate. To a solution of furo[2,3-b]pyridine-
2,5-dicarboxylic acid 5-ethyl ester19 (4.0 g, 17.01 mmol) in dry
DME (34 mL) cooled to -15 °C was added N-methylmorpholine
(1.87 mL, 17.01 mmol) and then isobutyl chloroformate (2.21
mL, 17.01 mmol). After 1 h, a solution of NaBH4 (1.93 g, 51.03
mmol) in water (20 mL) was carefully added dropwise. The
mixture was diluted with water (100 mL) and the aqueous was
extracted with EtOAc (3 × 100 mL), the combined organic
layer was washed with brine (1 × 30 mL), dried over MgSO4,
filtered and concentrated in vacuo. The yellow oil was purified
via column chromatography [40- × 150-mm column, gradient
elution Hex:EtOAc, 3:2 (1 L) to 1:1 (1 L) to 2:3 (1 L)] to provide
1.21 g (32% yield) of the title compound as a yellow solid: TLC
(Hex:EtOAc, 1:2) Rf ) 0.38; 1H NMR (400 MHz, CDCl3) δ 1.43
(t, J ) 7.1 Hz, 3H), 2.42 (br s, 1H), 4.43 (q, J ) 7.1 Hz, 2H),
4.84 (s, 2H), 6.76 (d, J ) 0.8 Hz, 1H), 8.54 (d, J ) 2.0 Hz, 1H),
8.98 (d, J ) 2.0 Hz, 1H). Following the procedure outlined in
method B, steps 3 and 4, then provided compound 27 as a
1
NH3:CH2Cl2, 10:30:60) Rf ) 0.44; H NMR (400 MHz, CDCl3)
δ 1.34 (s, 9H), 1.58-1.61 (m, 1H), 1.95-2.08 (m, 1H), 2.41-
3.11 (m, 10H), 3.45-3.98 (m, 7H), 4.23 (d, J ) 3.9 Hz, 1H),
5.26 (d, J ) 4.4 Hz, 1H), 6.27 (br s, 1H), 6.83 (d, J ) 2.4 Hz,
1H), 7.10-7.32 (m, 10H), 7.77 (s, 1H), 8.02 (br s, 1H), 8.36 (d,
J ) 1.9 Hz, 1H); MS (FAB-POSI) m/z 668 (M + 1). Anal.
(C38H45N5O6‚0.4H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(6-(4-ch lor o-5,7-d im eth ylp yr a zolo[3,4-b]-
p yr id yl)m et h yl)-2(S)-N′-(ter t-b u t ylca r b oxa m id o)p ip er -
a zin yl))p en ta n a m id e (24). 6-(Ch lor om eth yl)-4-ch lor o-5,7-
d im eth ylp yr a zolo[3,4-b]p yr id in e (15). Ethyl 4-chloro-5,7-
dimethylpyrazolo[3,4-b]pyridine-3-carboxylate is commercially
available from Maybridge Chemical Co. Following method B,
steps 2-4, compound 24 was prepared in 55% yield as a white
solid: mp 119-128 °C; TLC (MeOH:CHCl3 saturated with
NH3:CH2Cl2, 5:30:65) Rf ) 0.32; 1H NMR (400 MHz, CDCl3) δ
1.31 (s, 9H), 1.58-1.62 (m, 1H), 1.91-1.99 (m, 1H), 2.41-3.19
(m, 10H), 2.73 (s, 3H), 3.19-3.21 (m, 1H), 3.62-3.83 (m, 7H),
4.06 (s, 3H), 4.23-4.26 (m, 1H), 5.26 (dd, J ) 8.5, 4.9 Hz, 1H),
5.88 (d, J ) 8.5 Hz, 1H), 7.12-7.31 (m, 10H), 7.67 (br s, 1H),
8.38 (s,1H). Anal. (C39H50N7O4Cl) C, H, N.
white solid in 80% yield: mp 188-189 °C; [R]22 +0.65 (c )
D
1.00, CHCl3); TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2,
10:30:60) Rf ) 0.48; 1H NMR (400 MHz, CDCl3) δ 1.38 (s, 9H),
1.43 (t, J ) 7.0 Hz, 3H), 1.58-1.64 (m, 1H), 1.80 (br s, 2H),
1.94-1.99 (m, 1H), 2.44-2.58 (m, 2 H), 2.60-2.71 (m, 3H),
2.78-3.05 (m, 7H), 3.19 (br s, 1H), 3.66 (d, J ) 14.4 Hz, 1H),
3.76 (d, J ) 14.4 Hz, 1H), 3.76-3.82 (m, 1H), 4.27 (br s, 1H),
4.43 (q, J ) 7.0 Hz, 2H), 5.27 (dd, J ) 8.5, and 4.8 Hz, 1H),
6.03 (d, J ) 8.6 Hz, 1H), 6.71 (s, 1H), 7.10-7.29 (m, 10H),
8.01 (br s,1H), 8.53 (d, J ) 2.0 Hz, 1H), 8.99 (d, J ) 2.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 14.5, 29.2 (3C), 38.4, 39.3,
39.9, 47.1, 47.7, 51.5, 53.0, 54.4, 55.2, 57.7, 61.6 (2C), 63.9,
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(6-(5,7-d im eth ylp yr a zolo[3,4-b]p yr id yl)-

3396 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Dorsey et al.
66.0, 73.2, 105.6, 112.0, 123.1, 124.1, 125.4, 126.7, 127.0, 128.2,
128.7 (2C), 129.3 (2C), 131.7, 140.3, 140.6 (2C), 146.7, 155.3,
164.3, 165.6, 169.0, 175.0; MS (FAB-POSI) m/z 726 (M + 1).
Anal. (C41H51N5O7‚0.7H2O) C, H, N.
procedure outlined in method A, compound 31 was prepared
as a white solid in 78% yield: mp 101-110 °C; TLC (MeOH:
CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf ) 0.36; 1H
NMR (400 MHz, CDCl3) δ 1.36 (s, 9H), 1.49-1.58 (m, 1H),
1.91-2.01 (m, 1H), 2.25 (br s, 1H), 2.43-2.50 (m, 2H), 2.52-
2.62 (m, 4H), 2.64 (s, 3H), 2.70-3.03 (m, 7H), 3.09 (br s, 1H),
3.61 (d, J ) 14.1 Hz, 1H), 3.66 (d, J ) 14.1 Hz, 1H), 3.78-
3.86 (m, 1H), 4.14 (br s, 1H), 4.28 (dd, J ) 4.9, 3.9 Hz, 1H),
5.26 (dd, J ) 8.4, and 4.9 Hz, 1H), 6.43 (d, J ) 8.6 Hz, 1H),
6.62 (s, 1H), 7.05-7.29 (m, 10H), 7.92 (br s,1H), 8.70 (s, 1H);
HRMS (FAB-POSI; M + 1) calcd 668.3811, found 688.3803.
Anal. (C39H49N5O5) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(2-(5-h yd r oxym eth ylfu r o[2,3-b]p yr id yl)-
m et h yl)-2(S)-N′-(ter t-b u t ylca r b oxa m id o)p ip er a zin yl))-
p en ta n a m id e (28). A solution of ester 27 (0.635 g, 0.875
mmol) in dry THF (4 mL) at 0 °C was treated with LiBH4 (0.65
mL, 2.0 M in THF, 1.312 mmol). After 18 h, the reaction was
quenched with MeOH (20 mL) and the volatiles were removed
in vacuo. The residue was dissolved in EtOAc (150 mL) and
washed with saturated NaHCO3 (1 × 15 mL), water (1 × 15
mL), brine (1 × 15 mL), dried, filtered and concentrated. The
residue was purified via column chromatography [25- × 150-
mm column, gradient elution, CH2Cl2:CHCl3 saturated with
NH3:MeOH, 1% (0.5 L), 2% (0.5 L), 4% (0.5 L), 6% (0.5 L)].
The resulting solid was triturated with EtOAc and Hex to
afford 0.392 g (65% yield) of the title compound as a white
solid: mp 214-215 °C; TLC (MeOH:CHCl3 saturated with
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(3-t h ien o[2,3-b]p yr id ylm et h yl)-2(S)-N′-
(ter t-bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (32).
Following method A and using 3-formylthieno[2,3-b]pyridine34
and amine 2, the title compound was prepared as a white solid
in 56% yield: mp 101-110 °C; [R]22 +1.72 (c ) 1.00, CHCl3);
D
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf
1
) 0.48; H NMR (400 MHz, CDCl3) δ 1.26 (s, 9H), 1.48-1.58
NH3:CH2Cl2, 10:30:60) Rf ) 0.38; [R]22 +1.20 (c ) 1.00, CH3-
(m, 1H), 1.71 (br s, 1H), 1.95-2.03 (m, 1H), 2.37-2.45 (m, 1H),
2.48-3.07 (m, 12H), 3.67 (s, 2H), 3.76-3.90 (m, 2H), 4.24 (br
s, 1H), 5.26 (dd, J ) 8.5, and 4.8 Hz, 1H), 6.30 (d, J ) 8.6 Hz,
1H), 7.07-7.31 (m, 12H), 7.35 (s, 1H), 8.16 (dd, J ) 8.1, 1.5
Hz, 1H), 8.55 (dd, J ) 4.6, 1.6 Hz, 1H); 13C NMR (75.6 MHz,
CDCl3) δ 28.9 (3C), 38.0, 39.1, 39.6, 46.8, 48.6, 51.0, 52.5, 54.7,
56.3, 57.4, 61.4, 64.6, 65.9, 73.0, 119.2, 123.8, 125.1, 125.2,
126.5, 126.8, 128.0, 128.5 (2C), 129.0 (2C), 129.9, 130.0, 132.0,
139.9, 140.3 (2C), 146.8, 162.4, 169.6, 174.8; HRMS (FAB-
D
OH); 1H NMR (400 MHz, CDCl3) δ 1.37 (s, 9H), 1.55 (br s,
1H), 1.54-1.60 (m, 1H), 1.94-1.99 (m, 1H), 2.44-2.52 (m, 2
H), 2.59-2.64 (m, 3H), 2.77-3.05 (m, 9H), 3.15 (d, J ) 3.2
Hz, 1H), 3.62 (d, J ) 14.1 Hz, 1H), 3.72 (d, J ) 14.1 Hz, 1H),
3.78-3.81 (m, 1H), 4.10 (br s, 1H), 4.26 (br s, 1H), 4.76 (s, 2H),
5.25 (dd, J ) 8.6, and 3.7 Hz, 1H), 6.60 (s, 1H), 7.11-7.31 (m,
10H), 7.89 (d, J ) 2.0 Hz, 1H), 8.09 (br s,1H), 8.23 (d, J ) 2.0
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 29.1 (3C), 38.2, 39.3,
39.8, 46.5, 48.2, 51.5, 52.9, 54.4, 55.2, 57.7, 61.5, 62.7, 63.9,
66.0, 73.1, 105.4, 112.4, 124.2, 125.3, 126.6, 126.9, 128.1, 128.7
(2C), 129.2 (2C), 129.3, 132.7, 140.1, 140.6 (2C), 143.5, 154.2,
161.9, 169.5, 175.5; MS (FAB-POSI) m/z 684 (M + 1). Anal.
(C39H49N5O6‚0.25H2O) C, H, N.
POSI; M + 1) calcd 670.3427, found 670.3414. Anal. (C38H47
N5O4S‚0.2EtOAc) C, H, N.
-
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(2-t h ien o[2,3-b]p yr id ylm et h yl)-2(S)-N′-
(ter t-bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (33).
Following method A and using 2-formylthieno[2,3-b]pyridine34
and amine 2, the title compound was prepared as a white solid
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(2-fu r o[2,3-c]p yr idylm eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (29). From
2-formylfuro[2,3-c]pyridine32 and amine 2 and following the
procedure outlined in method A, the title compound was
prepared as a white solid in 67% yield: mp 100-106 °C; TLC
(MeOH:CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf ) 0.37;
1H NMR (400 MHz, CDCl3) δ 1.37 (s, 9H), 1.52-1.60 (m, 1H),
1.92-2.01 (m, 2H), 2.42-2.54 (m, 2H), 2.59-2.68 (m, 3H),
2.76-3.07 (m, 9H), 3.15 (br s, 1H), 3.67 (d, J ) 14.5 Hz, 1H),
3.72 (d, J ) 14.5 Hz, 1H), 3.78-3.86 (m, 1H), 4.04 (br s, 1H),
4.28 (s, 1H), 5.27 (dd, J ) 8.5, and 4.8 Hz, 1H), 6.28 (d, J )
8.6 Hz, 1H), 6.67 (s, 1H), 7.10-7.28 (m, 10H), 7.50 (d, J ) 5.2
Hz, 1H), 7.97 (br s, 1H), 8.39 (d, J ) 5.3 Hz, 1H), 8.78 (s, 1H);
HRMS (FAB-POSI; M + 1) calcd 654.3655, found 654.3670.
Anal. (C38H47N5O5‚0.2Hex) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(2-fu r o[3,2-c]p yr idylm eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (30). From
2-formylfuro[3,2-c]pyridine33 and amine 2 and following the
procedure outlined in method A, the title compound was
prepared as a white solid in 66% yield: mp 175-177 °C; TLC
(MeOH:CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf ) 0.41;
1H NMR (400 MHz, CDCl3) δ 1.37 (s, 9H), 1.52-1.61 (m, 1H),
1.94-1.99 (m, 1H), 2.44-2.53 (m, 3H), 2.61-2.66 (m, 3H),
2.76-3.03 (m, 8H), 3.17 (br s, 1H), 3.66 (d, J ) 14.3 Hz, 1H),
3.71 (d, J ) 14.3 Hz, 1H), 3.78-3.84 (m, 1H), 3.97 (br s, 1H),
4.25-4.27 (m, 1H), 5.27 (dd, J ) 8.6, and 4.9 Hz, 1H), 6.11
(dd, J ) 8.3, 0.4 Hz, 1H), 6.69 (s, 1H), 7.10-7.37 (m, 10H),
8.03 (br s,1H), 8.47 (d, J ) 5.7 Hz, 1H), 8.87 (s, 1H); HRMS
(FAB-POSI; M + 1) calcd 654.3655, found 654.3640. Anal.
(C38H47N5O5‚0.35H2O) C, H, N.
in 76% yield: mp 193-194 °C; [R]22 +1.68 (c ) 1.00, CHCl3);
D
TLC (MeOH:CHCl3 saturated with NH3:CH2Cl2, 10:30:60) Rf
1
) 0.42; H NMR (400 MHz, CDCl3) δ 1.42 (s, 9H), 1.54-1.62
(m, 1H), 1.79 (br s, 1H), 1.92-1.99 (m, 1H), 2.28-2.37 (m, 1H),
2.53-2.70 (m, 4H), 2.78-3.04(m, 9H), 3.47 (s, 1H), 3.73-3.84
(m, 3H), 3.95 (br s, 1H), 4.27 (d, J ) 4.6 Hz, 1H), 5.27 (dd, J
) 8.5, and 4.9 Hz, 1H), 6.05 (d, J ) 8.5 Hz, 1H), 7.10-7.32
(m, 10H), 7.75 (br s, 1H), 7.96 (dd, J ) 8.1, 1.7 Hz, 1H), 8.52
(dd, J ) 4.6, 1.7 Hz, 1H); 13C NMR (75.6 MHz, CDCl3) δ 29.2
(3C), 38.1, 39.0, 39.6, 46.8, 47.2, 51.3, 52.7, 54.7, 57.4, 58.5,
61.2, 63.8, 65.7, 72.9, 119.6, 120.5, 123.9, 125.1, 126.5, 126.7,
127.9, 128.5 (2C), 129.1 (2C), 130.6, 132.8, 140.0, 140.3, 140.4,
142.0, 146.4, 162.0, 168.9, 174.8; HRMS (FAB-POSI; M + 1)
calcd 670.3427, found 670.3422. Anal. (C38H47N5O4S‚0.25CHCl3)
C, H, N.
MK-944a : N-(2(R)-Hyd r oxy-1(S)-in d a n yl)-2(R)-p h en yl-
m eth yl-4(S)-h yd r oxy-5-(1-(4-(2-ben zo[b]fu r a n ylm eth yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e (34). To a solution of amine 2 (37 g, 63.71 mmol) and
commercially available benzofuran-2-carboxaldehyde (10 g,
70.08 mmol) dissolved in 700 mL of 1,2-dichloroethane was
added NaB(OAc)3H (24.9 g, 0.114 mol) portionwise followed
by AcOH (4 mL, 67.65 mmol). After 16 h the solvent was
removed in vacuo and the residue was dissolved in EtOAc (1.5
L). The organic layer was washed with saturated NaHCO3 (1
× 400 mL), H2O (3 × 350 mL), brine (1 × 200 mL), dried over
MgSO4, filtered and concentrated in vacuo to afford a yellow
foam. The residue was purified via column chromatography
[100- × 150-mm column, gradient elution CH2Cl2:CHCl3
saturated with NH3:iPrOH, 3% (4 L), 4% (4 L)]. A white solid
was recovered which was recrystallized from EtOAc/Hex to
provide 19.61 g (47% yield) as a white crystalline solid (a
second batch provided 7.6 g of material): mp 152-153.5 °C;
[R]22D +1.25 (c ) 1.00, CHCl3); TLC Rf (0.45, 5% MeOH in CH2-
Cl2 1/2 saturated with NH3); 1H NMR (400 MHz, CDCl3) δ 1.15
(d, J ) 3.6 Hz, 1H), 1.38 (s, 9H), 1.55-1.62 (m, 1H), 1.90-
1.96 (m, 1H), 2.41 (dd, J ) 10.8, 3.3 Hz, 1H), 2.49-2.59 (m,
2H), 2.64-2.94 (m, 9H), 2.96-3.05 (m, 1H), 3.21 (t, J ) 3.1
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(2-(6-m et h ylfu r o[3,2-c]p yr id yl)m et h yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e (31). The preparation of 2-formyl-6-methylfuro[3,2-c]-
pyridine followed in analogous fashion from the synthesis of
2-formylfuro[3,2-c]pyridine,33 using â-(3-furyl)methacrylic acid
in place of â-(3-furyl)acrylic acid. Starting from 2-formyl-6-
methylfuro[3,2-c]pyridine and amine 2 and following the

Identification of MK-944a
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3397
Hz, 1H), 3.62 (d, J ) 13.9 Hz, 1H), 3.91 (d, J ) 13.9 Hz, 1H),
3.77-3.82 (m, 1H), 3.99 (br s, 1H), 4.11-4.29 (m, 1H), 5.28
(dd, J ) 4.8, 8.5 Hz, 1H), 5.95 (d, J ) 8.6 Hz, 1H), 6.61 (s,
1H), 7.09-7.32 (m, 11H), 7.40-7.42 (m, 1H), 7.53-7.55 (m,
1H), 8.26 (br s, 1H); 13C NMR (75.6 MHz, CDCl3) δ 29.0 (3C),
38.1, 39.1, 39.6, 46.6, 47.2, 51.1, 52.7, 54.2, 54.9, 57.5, 61.3,
63.5, 65.6, 72.9, 106.1, 111.0, 120.9, 122.8, 123.9, 124.3, 125.1,
126.4, 126.7, 127.9, 128.0, 128.4 (2C), 129.1 (2C), 140.0, 140.4
(2C), 153.3, 155.1, 168.9, 174.9; HRMS (FAB-POSI; M + 1)
calcd 653.3702, found 653.3721. Anal. (C39H48N4O5) C, H, N.
148.1, 154.0, 168.8, 174.8; MS (FAB-POSI) m/z 667 (M + 1).
Anal. (C40H50N4O5) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(2-b en zim id a zolylm et h yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (37). Fol-
lowing method B, step 4, and using 2-(chloromethyl)benzimida-
zole and amine 2, the title compound was prepared as a white
solid in 58% yield: mp 127-133 °C; TLC (MeOH:CHCl3
saturated with NH3:CH2Cl2, 10:30:60) Rf ) 0.37; 1H NMR (300
MHz, CDCl3) δ 1.42 (s, 9H), 1.58-1.68 (m, 3H), 1.97-2.09 (m,
1H), 2.53-3.19 (m, 15H), 3.15 (br s, 1H), 3.82 (d, J ) 14.5 Hz,
1H), 3.89 (d, J ) 14.5 Hz, 1H), 4.21-4.28 (m, 1H), 5.25-5.29
(m, 1H), 6.09 (d, J ) 8.5 Hz, 1H), 7.09-7.34 (m, 14H), 7.60 (d,
J ) 3.1 Hz, 1H), 7.62 (d, J ) 3.2 Hz, 1H); MS (FAB-POSI) m/z
653 (M + 1). Anal. (C40H50N4O5‚0.55CHCl3) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(2-b en zim id a zolylm et h yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (38). Fol-
lowing method A and using indole-3-carboxaldehyde and
amine 2, the title compound was prepared as a white solid in
41% yield: mp 125-131 °C; TLC (MeOH:CHCl3 saturated with
NH3:CH2Cl2, 5:30:65) Rf ) 0.43; 1H NMR (400 MHz, CDCl3) δ
1.25 (s, 9H), 1.54-1.60 (m, 3H), 1.62 (br s, 1H), 1.89-1.94 (m,
1H), 2.33 (br s, 1H), 2.48-2.54 (m, 2H), 2.61-3.05 (m, 10H),
3.17 (br s, 1H), 3.68 (2, 2H), 3.78 (br s, 1H), 4.27 (t, J ) 4.4
Hz, 1H), 5.27 (dd, J ) 8.1, 5.0 Hz, 1H), 5.97 (d, J ) 8.4 Hz,
1H), 7.10-7.31 (m, 12H), 7.38 (d, J ) 8.1 Hz, 1H), 7.63 (d, J
) 7.7 Hz, 1H), 7.98 (br s, 1H), 8.20 (s, 1H); HRMS (FAB-POSI;
M + 1) calcd 652.3862, found 652.3866. Anal. (C40H50N4O5‚
1.0EtOAc) C, H, N.
MK-944a : N-(2(R)-Hyd r oxy-1(S)-in d a n yl)-2(R)-p h en yl-
m eth yl-4(S)-h yd r oxy-5-(1-(4-(2-ben zo[b]fu r a n ylm eth yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e Hyd r och lor id e Dih yd r a te. To MK-944a (1.11 g, 1.70
mmol) dissolved in 16 mL of absolute ethanol cooled to 0 °C
was added 1.70 mL of 1 N HCl (1.70 mmol) dropwise. After
30 min the solvent was removed in vacuo to provide a white
foam. This foam was suspended in H2O and the pH was
adjusted to 2 with 1 N HCl. After 48 h the solid was filtered
and washed with cold H2O to provide 1.06 g of a white
crystalline solid (86% yield): mp 128-133 °C. Anal. (C39H48
N4O5‚1.0HCl‚1.90H2O) C, H, N.
-
MK-944a : N-(2(R)-Hyd r oxy-1(S)-in d a n yl)-2(R)-p h en yl-
m eth yl-4(S)-h yd r oxy-5-(1-(4-(2-ben zo[b]fu r a n ylm eth yl)-
2(S )-N ′-(t er t -b u t ylca r b oxa m id o)p ip e r a zin yl))p e n t a n -
a m id e Mesyla te. To MK-944a (1.0 g, 1.53 mmol) dissolved
in 15 mL of absolute ethanol cooled to 0 °C was added methane
sulfonate (0.10 mL, 1.53 mmol) dropwise. After 30 min the
solvent was removed in vacuo to provide a white foam. This
foam was suspended in 50 mL of EtOAc, aged 3 h and filtered
to provide a white solid. This was dried at 50 °C for 18 h to
afford 1.064 g (93% yield) of a white crystalline solid: mp 153-
155.5 °C. Anal. (C39H48N4O5‚1.0CH3SO3H‚0.40H2O) C, H, N.
N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h yd r oxy-5-(1-(4-(5-ben zo[b]fu r a n ylm eth yl)-2(S)-N′-(ter t-
bu tylca r boxa m id o)p ip er a zin yl))p en ta n a m id e (35). Ethyl
benzofuran-5-carboxylate was converted into 5-(chloromethyl)-
benzo[b]furan following the procedures outlined in method B,
steps 2 and 3. Benzofuran 35 was prepared following the
procedures outlined in method B, step 4, utilizing amine 2 and
5-(chloromethyl)benzo[b]furan. This provided the title com-
pound as a white solid in 56% yield: mp 105-110 °C; TLC
(MeOH:CHCl3 saturated with NH3:CH2Cl2, 5:30:65) Rf ) 0.41;
1H NMR (400 MHz, CDCl3) δ 1.36 (s, 9H), 1.56-1.61 (m, 1H),
1.68 (br s, 2H), 1.94-1.99 (m, 1H), 2.24-2.36 (m, 1 H), 2.46-
2.52 (m, 2H), 2.62-3.05 (m, 10H), 3.17 (t, J ) 3.0 Hz, 1H),
3.53 (d, J ) 12.5 Hz, 1H), 3.56 (d, J ) 12.5 Hz, 1H), 3.72-
3.82 (m, 1H), 4.26-4.29 (m, 1H), 5.25-5.29 (m, 1H), 5.99 (d,
J ) 8.4 Hz, 1H), 6.73 (dd, J ) 1.3, 0.8 Hz, 1H), 7.09-7.32 (m,
10H), 7.46 (s, 1H), 7.48 (s, 1H), 7.64 (d, J ) 2.0 Hz, 1H), 8.12
(br s, 1H); HRMS (FAB-POSI; M + 1) calcd 653.3702, found
653.3702. Anal. (C39H48N4O5‚0.65H2O) C, H, N.
Ack n ow led gm en t. We acknowledge the leadership
provided by Dr. Paul S. Anderson.We also thank Process
Chemistry (Rahway, NJ ) for generous supplies (kilo-
gram quantities) of several intermediates which greatly
facilitated the identification of MK-944a. Finally, we
gratefully acknowledge the contributions of Mr. J ohn
Moreau, Ms. Patrice Ciecko, Mr. Ken Anderson, Mr.
Matthew Zrada (solubility, log P determinations, el-
emental analysis), Mr. Art Coddington (mass spectrom-
etry), and Ms. J ean Kaysen (manuscript preparation).
Su p p or tin g In for m a tion Ava ila ble: Elemental analyses
of compounds 3-8 and 19-36. This material is available free
of charge via the Internet at http://pubs.acs.org.
Refer en ces
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N-(2(R)-Hydr oxy-1(S)-in dan yl)-2(R)-ph en ylm eth yl-4(S)-
h ydr oxy-5-(1-(4-(2-(3-m eth ylben zo[b]fu r an yl)m eth yl)-2(S)-
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compound as a white solid in 76% yield: mp 111-118 °C; [R]22
D
+1.03 (c ) 1.00, CHCl3); TLC (MeOH:CHCl3 saturated with
1
NH3:CH2Cl2, 10:30:60) Rf ) 0.54; H NMR (400 MHz, CDCl3)
δ 1.35 (s, 9H), 1.52-1.60 (m, 1H), 1.72 (br s, 2H), 1.87-1.97
(m, 1H), 2.23 (s, 3H), 2.34-2.42 (m, 1 H), 2.45-3.04 (m, 11H),
3.15 (br s, 1H), 3.57 (d, J ) 13.5 Hz, 1H), 3.61 (d, J ) 13.5 Hz,
1H), 3.73-3.82 (m, 1H), 4.06 (br s, 1H), 4.25-4.30 (m, 1H),
5.25-5.29 (m, 1H), 6.23 (d, J ) 8.6 Hz, 1H), 7.11-7.30 (m,
11H), 7.38 (d, J ) 7.2 Hz, 1H), 7.49 (d, J ) 7.3 Hz, 1H), 8.29
(br s, 1H); 13C NMR (75.6 MHz, CDCl3) δ 7.9, 28.8 (3C), 38.0,
39.0, 39.5, 46.6, 47.0, 51.0, 52.3, 52.5, 54.0, 57.4, 61.2, 63.3,
65.5, 72.8, 110.7, 114.1, 119.3, 122.3, 123.8, 124.3, 125.0, 126.3,
126.6, 127.8, 128.3 (2C), 129.0 (2C), 129.4, 139.9, 140.3 (2C),
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