Solid phase assisted synthesis of HIV-1 inhibitors. Expedient entry to unsymmetrical substitution of a C2 symmetric template

Article abstract of DOI:10.1139/v00-012

A solid phase synthesis has been developed leading up to unsymmetrical HIV-1 protease inhibitors that are not readily available by conventional solution phase chemistry (18a-g). To prepare these compounds the hydroxyl group of (1s,2r)-(-)-cis-1-phthalimido-2-indanol (3) was coupled to a Merrifield resin via a dihydropyrane linker. Cleavage of the phthalimido protecting group and reaction of the liberated amine with the bis-activated symmetrical diacid 15 resulted in the resin bound amide 16. Coupling of 16 with amino acids and amines followed by hydrolysis produced the desired unsymmetrical products 18a-g from which potent HIV-1 protease inhibitors were identified, e.g., 18e (k(i) = 0.1 nM), 18a (k(i) = 0.2 nM) and 18c (k(i) = 2 nM).

Full text of DOI:10.1139/v00-012

829
Solid phase assisted synthesis of HIV-1 protease
inhibitors. Expedient entry to unsymmetrical
substitution of a C2 symmetric template
Karin Oscarsson, Björn Classon, Ingemar Kvarnström, Anders Hallberg,
and Bertil Samuelsson
Abstract: A solid phase synthesis has been developed leading up to unsymmetrical HIV-1 protease inhibitors that are
not readily available by conventional solution phase chemistry (18a–g). To prepare these compounds the hydroxyl
group of (1S,2R)-(–)-cis-1-phthalimido-2-indanol (3) was coupled to a Merrifield resin via a dihydropyrane linker.
Cleavage of the phthalimido protecting group and reaction of the liberated amine with the bis-activated symmetrical
diacid 15 resulted in the resin bound amide 16. Coupling of 16 with amino acids and amines followed by hydrolysis
produced the desired unsymmetrical products 18a–g from which potent HIV-1 protease inhibitors were identified, e.g.,
18e (ki = 0.1 nM), 18a (ki = 0.2 nM) and 18c (ki = 2 nM).
Key words: HIV, inhibitor, protease, solid phase.
Résumé : On a mis au point une synthèse en phase solide qui permet d’obtenir des inhibiteurs non symétriques de
protéase HIV-1 (18a–g) qu’il est difficile d’obtenir par la chimie conventionnelle en solution. Dans cette synthèse, on
couple le groupement hydroxyle du (1S,2R)-(–)-cis-1-phtalimido-indan-2-ol (3) à une résine de Merrifield à l’aide d’une
liaison avec un dihydropyrane. Après clivage du groupe phtalimido protecteur et réaction de l’amine libérée avec le
diacide symétrique 15 doublement activé, on obtient l’amide 16 lié à la résine. Le couplage de 16 avec des acides
aminés ou avec des amines suivi d’une hydrolyse permet d’obtenir les produits non symétriques désirés 18a–g à partir
desquels il a été possible d’identifier de puissants inhibiteurs de protéase de l’HIV-1, par exemple 18e (ki = 0,1 nM),
18a (ki = 0,2 nM) et 18c (ki = 2 nM).
Mots clés : HIV, inhibiteur, protéase, phase solide.
[Traduit par la Rédaction] Oscarsson et al. 837
Introduction
the high frequency of mutations in the HIV genome eventu-
ally results in the selection of mutant strains and in develop-
ment of clinical resistance (5, 13–15). Moreover, the high
cost of therapy precludes the widespread use of the currently
approved HIV-1 protease inhibitors. Not withstanding the
progress achieved to date there is thus a pressing need for
the development of new and cost-effective HIV-1 protease
inhibitors.
We recently reported on the design, synthesis, and antivi-
ral activity of new carbohydrate based C2-symmetrical prote-
ase inhibitors e.g., compounds 1 and 2 (Table 1) (16) which
are readily prepared in three steps from commercially avail-
able starting materials. However, to prepare unsymmetrical
inhibitors based on the C2-symmetric core template (Fig. 1),
a new synthetic procedure had to be developed, as treatment
The human immunodeficiency virus (HIV) has been iden-
tified as the etiologic agent of AIDS (1, 2). The HIV-1 prote-
ase is a member of the aspartic protease family of enzymes
(3–5), producing essential structural and functional viral pro-
teins by proteolytic processing of the gag- and gag-pol viral
gene products (6, 7). Inhibition of the HIV-1 PR have been
shown to lead to the inactivation of HIV-1 (4, 8–10). Nota-
bly, protease inhibitors have shown clinical efficacy and
there are presently five protease inhibitors approved by the
FDA for the treatment of HIV-1 infection: saquinavir, riton-
avir, indinavir, nelfinavir, and amprenavir (11, 12). Whereas
these inhibitors effectively reduce the plasma viral load in
infected individuals (11), the rapid turnover of HIV-1 and
Received June 29, 1999. Published on the NRC Research Press Website on June 13, 2000.
Dedicated to Professor Stephen Hanessian in recognition of his outstanding contribution to the art and logic of organic synthesis.
K. Oscarsson, B. Classon, and B. Samuelsson.1 Dept. of Organic Chemistry, Arrhenius Laboratory, Stockholm University,
SE-106 91 Stockholm, Sweden.
I. Kvarnström. Dept. of Chemistry, Linköping University, S-581 83 Linköping, Sweden.
A. Hallberg. Dept. of Organic Pharmaceutical Chemistry, Uppsala University, BMC, S-751 23 Uppsala, Sweden.
1Author to whom correspondence may be addressed. Telephone: +46 8 6083100. Fax: +46 8 6083199.
e-mail: bertil.samuelsson@medivir.se
1Additional address: Medivir AB, Lunastigen 7, SE-14144 Hudding, Sweden.
Can. J. Chem. 78: 829–837 (2000)
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Can. J. Chem. Vol. 78, 2000
Scheme 1. Synthesis of protected (1S,2R)-(–)-cis-1-amino-2-indanol.
Table 1. C2-symmetrical protease inhibitors.
Figure 1. Unsymmetrical inhibitors, A = Amines.
the free amino function which was reacted with the bis-
activated L-mannaric acid (15) resulting in the resin bound
monoactivated amide 16. Coupling of 16 with a selection of
amines, followed by hydrolysis gave the desired products
18a–g and 1. Not withstanding this selectivity, a minor
amount of the symmetrical inhibitor 1 was formed from “in-
land” cross- coupling as evidenced by analysis of the prod-
ucts formed in the reaction. Notably the present solid phase
chemistry methodology opens up for further developments
of this class of compounds using combinatorial chemistry
(22, 23). The compounds produced were screened for HIV-1
protease inhibition and for anti HIV-1 activity in a cell cul-
ture assay.
Results and discussion
Chemistry
The phthalimido derivative 5 was prepared in two steps by
reacting compound 3 with phthalic anhydride in the pres-
ence of triethylamine in methanol followed by pyridine –
acetic anhydride to give 4 in 83% yield. Deacetylation with
sodium methoxide in methanol–dichloromethane gave 5 in
65% yield (Scheme 1). The protected amino indanol 5 was
coupled to the solid support 3,4-dihydro-2H-2-ylmethoxy-
methyl polystyrene (6) in 1,2-dichloroethane using pyridinium
p-toluenesulfonate (PPTS) (24) as a catalyst to give 7
(Scheme 2) (22). The phthalimido protecting-group was there-
after cleaved off using methylamine in ethanol for 16 h to
give the free amine 8 and the liberated N-methyl phthalimide
(9) in solution. The loading onto the solid support was cal-
culated to be 66% based on the recovery of 9.
of either the bislactone (10) or the activated L-mannaric acid
(15) with amines at various conditions preferentially gives
the symmetrical products with only minor amounts of the
monosubstituted product being present in the reaction mix-
ture at any given time. We now report on the use of solid
phase synthesis to prepare unsymmetrical protease inhibitors
based on the previously disclosed C2-symmetric core tem-
plate (16). The amino indanol 3 has been shown by others
(17–19) and us (16) to be an excellent P2/P2′ ligand for the
S2/S2′ pockets of the HIV-1 protease. Thus in the present
work the amino indanol P2 residue (3) has been kept con-
stant while the P2′ residue has been varied using parallel
synthesis (Fig. 1). The protected amino indanol 5 was cou-
pled to a THP linker (20) on a Merrifield resin (21), fol-
lowed by deprotection of the phthalimido group liberating
Initial attempts to react the bislactone (10) (16) (lactone
ring opening) with the free amino group on the solid support
8 failed to give satisfactory results due to unexpected low re-
activity under standard reaction conditions (dichloromethane,
reflux). Instead an alternative route was investigated
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Oscarsson et al.
831
Scheme 2. Coupling of protected (1S,2R)-(–)-cis-1-amino-2-indanol to Merrifield resin.
employing the bissuccinimidyl ester (15) (16) for which a
new and improved synthetic route was developed. Benzylated
bislactone (10) (16) was thus reacted with methylamine cat-
alyzed by 2-hydroxypyridine to give bisamide (11) in 87%
yield (Scheme 3). Use of 2-hydroxypyridine (25) as a cata-
lyst for this reaction gave the highest yields due to suppres-
sion of a β-elimination side reaction. The diol in compound
11 was protected using 2,2-dimethoxypropane in acetone
containing camphorsulfonic acid to give 12 in 85% yield
(16). The corresponding dicarboxylic acid (14) was prepared
in essentially quantitative yield by reacting compound 12
with dinitrogen tetraoxide (26) and anhydrous sodium ace-
tate in dichloromethane (27, 28) to provide the bis-[N-nitro-
soamide] (13), which was hydrolyzed with lithium hydroxide
and hydrogen peroxide (29, 30) to furnish the dicarboxylic
acid (14). Activation of 14 with N,N-disuccinimidyl carbon-
ate delivered the corresponding activated bissuccinimidyl es-
ter (15) in 95% yield (16).
The amino indanol on the solid support (8), was reacted
with compound 15 to give the monoamide 16 (Scheme 4)
and subsequent coupling of 16 with a series of amines (A =
amine, Table 2) gave the unsymmetrical products 17a–g as
well as the symmetrical product 17h linked to solid support.
Hydrolysis with 2.3 M HCl in methanol produced com-
pounds 18a–g together with the symmetrical inhibitor 1. The
yields of pure products (18a–g) over the three steps, based
on the loading of the solid support, ranged from 17–47%.
Approximately 4% yield of symmetrical inhibitor 1 isolated
by chromatography, was formed in each reaction (Table 2).
quantified using vital dye XTT (33). The 50% inhibitory
concentrations (ED50) were calculated from the percent
cytoprotection for individual compounds.
Structure activity relationship
From Table 2 it is evident that unsymmetrical L-mannaric
amides of simple structures can be potent HIV-1 protease in-
hibitors. The potency of inhibitor 18e (Ki = 0.1 nM) is some-
what surprising. The P2′ benzyl group of inhibitor 18e can
be viewed as a truncated P2′ amino indanol of 1 lacking the
conformational rigidity of the amino indanol and lacking the
hydrogen bond of the corresponding amino indanol hydroxyl
group to the Asp 29 of the HIV-1 protease (16). Indeed, the
X-ray crystal structure of 18e complexed with HIV-1 prote-
ase shows that the phenyl group is superimposed onto the
aryl part of the corresponding amino indanol in inhibitor 1.2
However, substitution of the benzyl P2′ residue with hydro-
gen bond accepting or electron donating groups as in the in-
hibitors 18f and 18g leads to less active compounds. These
results correlate well with earlier observations, that aromatic
substitutions lead to less active inhibitors (15).
Inhibitor 18a has similar potency (ki = 0.2 nM) as the
potent corresponding symmetrical inhibitors 1 (ki = 0.4 nM)
and 2 (ki = 0.6 nM) (16). Inhibitors 18b, 18c, and 18d are
P2′ truncated simplified analogues of 18a. Both 18b and 18d
are considerably less potent, while the methyl amide 18c (ki
= 2 nM) is notably potent. This inhibitor effectively lacks a
P2′ residue and the high potency presumably results from an
energetically more favorable hydrogen bond interaction be-
tween the methyl amide carboxyl oxygen and the structural
water that is tetra- coordinated to the inhibitor carbonyls and
the Ile 50/150 residues of the HIV-1 protease.
HIV-1 protease inhibition
(Table 1 and 2) HIV-1 protease was cloned and hetero-
logously expressed in Escherichia coli (31). Ki-values were
determined in a fluorometric assay (32).
In spite of the promising HIV-1 protease inhibition activi-
ties obtained for some of these inhibitors, the antiviral activ-
ities in cell culture (ED50) were not improved over inhibitor
1 although inhibitor 18a was equipotent (Table 2). Further
studies are necessary to rationalize the SAR for antiviral ac-
tivity in cell culture for this class of compounds (34, 35).
In vitro anti-HIV activity
(Table 1 and 2) The anti-HIV activity was assayed by a
HIV cytopathic assay in MT-4 cells where the effects were
2 Unpublished results.
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Can. J. Chem. Vol. 78, 2000
Scheme 3. Synthesis of bissuccinimidyl ester.
(1S,2R)-(–)-cis-1-Phthalimido-2-O-acetoxy (4)
Experimental section
A mixture of 3 (3.0 g, 20 mmol), phthalic anhydride
(3.6 g, 24.3 mmol), and triethylamine (2.8 mL, 20.0 mmol)
in MeOH (50 mL) was stirred at room temperature for
70 min under an argon atmosphere. After concentration the
oily residue was dissolved in pyridine (40 mL) and acetic
anhydride (20 mL) and stirred at room temperature for 16 h.
The mixture was worked-up by adding CH2Cl2 (100 mL)
extracted with cold 10% HCl (2 × 40 mL). The combined
aqueous phases were washed with CH2Cl2 (2 × 50 mL) and
the organic layer was washed with saturated NaHCO3 (2 ×
100 mL) and saturated NaCl (2 × 100 mL). The combined
aqueous phases were washed with CH2Cl2 (2 × 75 mL),
dried and concentrated. The crude product was purified us-
ing column chromatography (toluene – ethyl acetate, 15:1)
Thin layer chromatography was performed using silica gel
60 F-254 (Merck) plates with detection by UV and (or) char-
ring with 8% sulphuric acid or by charring with ammonium
molybdate (100 g):Cer(IV)sulfate (2 g):sulfuric acid (10%,
2 L). Column chromatography was performed on silica gel
(Matrix Silica Si 60A, 35–70m, Amicon). Organic phases
were dried over anhydrous sodium sulfate or magnesium sul-
phate. Concentrations were performed under reduced pres-
sure. NMR spectra were recorded on a JEOL GSX-270
1
instrument (13C NMR 67 MHz and H NMR 270 MHz).
Chemical shifts are reported in ppm (δ) downfield from
tetramethylsilane in CDCl3, unless otherwise stated. Accu-
rate mass measurements were recorded on a Finnigan MAT
900S Electrospray. Mass spectra were recorded on a
Hewlett–Packard 1100MSD.
1
to give 4 (5.3 g 83%) as a yellow solid. H NMR (CDCl3) δ:
1.86 (s, 3H, 1 CH3), 3.46–3.49 (t, 2H, 1 CH2), 5.64–5.72 (q,
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Oscarsson et al.
833
Scheme 4. Synthesis of L-mannaric diamides.
1H, 1 CH), 5.96–5.99 (d, 1H, 1 CH), 7.20–7.32 (m, 4H, Ar),
7.71–7.86 (m, 4H, Ar). 13C NMR (67MHz, CDCl3) δ: 20.3
(CH3), 37.7 (CH2), 54.4 (CH-N), 72.6 (CH-O), 123.0, 124.3,
124.5, 126.9, 128.7, 131.4, 133.8, 136.4, and 140.6 (aro-
matic C), 167.4 and 168.9 (C=O). MS (API-ES) calcd. for
321.10; found: 321.1.
(1S,2R)-(–)-cis-1-Amino-2-indanol on solid support (8)
Methylamine in ethanol (4.5 mL, 33%) was added to the
solid phase from the previous step (7) and stirred for 16 h.
The solid phase was rinsed with CH2Cl2 (10 mL), MeOH
(10 mL), and then CHCl3 (10 mL) to give 8. All the solid
phase will be used in the subsequent step.
The combined organic phases were concentrated and the
formed N-methylphthalimide (9) was purified using column
chromatography (chloroform–methanol, 20:1) which gave
(1S,2R)-(–)-cis-1-Phthalimido-2-indanol (5)
To a stirred solution of 4 (5.3 g, 16 mmol) in MeOH
(250 mL) and CH2Cl2 (100 mL), sodium methoxide in MeOH
(0.1 M) was added dropwise until pH reached 7.5. After 5 h
Dowex® HCR-W2 (H+) ion exchange resin was added to neu-
tralize the solution. The product was purified using column
chromatography (toluene – ethyl acetate, 5:1). Concentration
gave pure 5 (2.98 g, 65%) as a white solid. 1H NMR (CDCl3)
δ: 2.84 (s, 1H, 1 OH), 3.20–3.38 (m, 2H, 1 CH2), 4.75–4.77
(q, 1H, CHOH), 5.77–5.80 (d, 1H, CHN), 7.09–7.33 (m, 4H,
Ar), 7.67–7.83 (m, 4H, Ar). 13C NMR (67MHz, CDCl3) δ:
41.2 (CH2), 57.7 (CH-N), 74.0 (CH-OH), 123.4, 124.2, 125.5,
126.9, 128.5, 131.8, 134.1, 137.1, and 140.2 (aromatic C),
169.0 (C=O). Anal. calcd. (C17H13NO3): C 73.11, H 4.69,
N 5.02; found: C 72.98, H 4.55, N 4.98.
1
pure 9 as a white solid (21 mg, loading 66%). H NMR
(270 MHz, CDCl3) δ: 2.94 (s, 3H, 1 CH3), 7.01–7.67 (m,
4H, Ar). 13C NMR (67MHz, CDCl3) δ: 26.8 (CH3), 125.7,
128.3, 129.0, 130.1, 134.6, and 140.7 (aromatic C), 170.0
(C=O).
N1,N6-Dimethyl-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-
dihydroxy hexanediamide (11)
A mixture of benzylated bislactone (10) (7.64 g, 21.6 mmol),
2-hydroxypyridine (2.06 g, 21.7 mmol), and methylamine in
THF (2 M, 23 mL, 46 mmol) in CHCl3 (60 mL) was stirred
at ambient temperature for 15 min. The organic phase was
washed with saturated NaHCO3 (3x), dried, concentrated, and the
residue purified by column chromatography (CHCl3–MeOH,
20:1) to give pure 11 (7.83 g, 18.8 mmol, 87%) as a white
solid. 13C NMR (CDCl3) δ: 25.8 (2 CH3-NH), 71.1, 73.8,
79.6 (2 OCH2Ph, C2, C3, C4, and C5), 128.1, 128.2,
128.6, 136.7 (aromatic C), 172.7 (2 C=O). MS (API-ES)
calcd. for 416.1; found: 416.1.
(1S,2R)-(–)-cis-1-Phthalimido-2-indanol on solid support (7)
Dry Merrifield resin with a dihydropyran linker (6)
(400 mg, 0.51 mmol/g, 0.20 mmol linker) was swollen in
dry 1,2-dichloroethane (5.5 mL) under an argon atmosphere.
Anhydrous PPTS (100 mg, 0.40 mmol) and 5 (200 mg,
0.72 mmol) were added and the mixture was heated to 79°C.
After 16 h the mixture was cooled to room temperature and
the solid support was rinsed with CH2Cl2 (20 mL) and
MeOH (20 mL) to give 7. The filtrate was concentrated and
the solid residue was purified using column chromatography
(toluene – ethyl acetate, 5:1) to recover unreacted 3
(104 mg, 0.47 mmol). All the solid phase was used in the
subsequent step.
N1,N6-Dimethyl-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-
dihydroxy-3,4-O-isopropylidenehexanediamide (12)
Dimethoxypropane (15 mL, 123 mmol) and camphorsul-
fonic acid (2.66 g, 11.5 mmol) were added to a stirred mix-
ture of 11 (6.0 g, 14.4 mmol) in dry acetone (70 mL). The
precipitated product was filtered off after 15 min to give
pure 12. The solution was concentrated, CH2Cl2 was added
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Can. J. Chem. Vol. 78, 2000
Table 2. Structure, yields, and HIV-1 protease inhibitory acitivity and in vitro antiHIV-1
acitvity of unsymmetrical L-mannaric diamides with 2R, 3R, 4R, 5R configuration.
to the residue, and the organic phase was washed with satu-
rated NaHCO3 (3x), dried and concentrated. The solid was
washed with a small amount of dry, cold acetone to give
pure 12 (5.58 g, 12.2 mmol, 85%). 13C NMR (CDCl3) δ:
25.6, 26.9 (4 CH3), 73.5, 77.5, 79.3 (2 OCH2Ph, C2, C3, C4,
and C5), 110.0 (O-C-O), 128.0, 128.1, 128.5, 136.8 (aro-
matic C), 169.3 (C=O). Anal. calcd. (C25H32N2O6): C 65.77,
H 7.06. N 6.14; found: C 65.65, H 6.83, N 6.01.
N1,N6-Dimethyl-N1,N6-dinitroso-(2R,3R,4R,5R)-2,5-
dibenzyloxy-3,4-dihydroxy-3,4-O-
isopropylidenehexanediamide (13)
To produced N2O4, Pb(NO3)2 (20 g, 60 mmol) was heated
over an open flame and the gas was led down into CH2Cl2 at
–10°C. The solution was cooled to –60°C under an argon at-
mosphere and anhydrous sodium acetate (4.2 g, 51.2 mmol)
was added followed by 12 (3.25 g, 7.12 mmol). The –60°C
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Oscarsson et al.
835
bath was replaced with an ice salt bath after 30 min and the
mixture was stirred at –10°C until the substrate was con-
sumed (1 h). The solution was poured into ice and water and
the phases were separated. The organic phase was washed
with ice cold 5% sodium bicarbonate. The organic phase
was washed with ice cold 5% sodium bicarbonate, dried
briefly at 0°C, and concentrated to give 13 as a yellow oil.
The nitrosoamide solution was never allowed to warm above
0°C. All the product was used immediately in the next step.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2-
hydroxyethyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-
dihydroxy-3,4-O-isopropylidenehexanediamide on solid
support (17c)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine ethanolamine
(120 µL, 2 mmol) to give 17c.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-
2,5-Di-O-benzyl-3,4-O-isopropylidene-L-mannaric acid (14)
Hydrogen peroxide (12.5 g 30%) and LiOH (1.26 g,
52.7 mmol) were added to a stirred solution of 13 from the
previous step in THF–H2O (3:1) (100 mL) at 0°C. The mix-
ture was stirred for 20 min at 0°C. The reaction was quenched
with Na2SO3 (15 mL, 1.5 M). The THF was evaporated and
the water phase was acidified with Dowex® HCR-W2 (H+)
ion exchange resin, and extracted with EtOAc. The phases
were separated and the organic phase was dried and concen-
trated to give 14 (3.05 g, 7.08 mmol, 100%) as a white solid.
13C NMR (CD3OD) δ: 27.5 (2 CH3), 73.6, 80.0, 80.3
(2 OCH2Ph, C2, C3, C4, and C5), 112 (O-C-O), 129.0,
129.3, 129.4, 138.5 (aromatic C), 173.1 (C=O).
(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-dihydroxy-3,4-O-
isopropylidenehexanediamide on solid support (17d)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine valine methylamide
(195 mg, 1.5 mmol) to give 17d.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2,4-
difluorobenzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-
dihydroxy-3,4-O-isopropylidenehexanediamide on solid
support (17e)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine 2,4-difluorobenzyl-
amine (240 µL, 2.02 mmol) to give 17e.
N1-[(2R)-Hydroxy-1(S)indanyl]-N6-succinimidyl-
(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-dihydroxy-3,4-O-
isopropylidenehexanediamide on solid support (16)
The solid phase from the previous step (8) was swollen in
dry 1,2-dichloroethane (4.5 mL) for 40 min under an argon
atmosphere. The bissuccinimidyl diester (15) (900 mg,
1.44 mmol) was added and the mixture was stirred for 16 h
under an argon atmosphere at 60°C. The solid phase was
rinsed with CHCl3 (20 mL), THF (10 mL), and then 1,2-
dichloroethane (10 mL) to give 16. All the solid phase was
used in the subsequent step.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(benzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-dihydroxy-
3,4-O-isopropylidenehexanediamide on solid support (17f)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine benzylamine
(220 µL, 2.01 mmol) to give 17f.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2-
methoxybenzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-
dihydroxy-3,4-O-isopropylidenehexanediamide on solid
support (17h)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine 2-methoxybenzyl-
amine (250 µL, 1.92 mmol) to give 17h.
General procedure for preparation of compounds 17a–h
The solid phase from the previous step (16) was swollen
in dry 1,2-dichloroethane (4 mL) for 40 min under an argon
atmosphere. The amine (2.0 mmol) was added and the mix-
ture was stirred for 16 h under argon at 60°C. The solid
phase was rinsed with CHCl3 (20 mL), THF (10 mL), and
then 1,2-dichloroethane (10 mL) to give 17a–h. All the solid
phase was used in the subsequent step.
N1,N6-Di[(2R)-hydroxy-1(S)-indenyl]-(2R,3R,4R,5R)-2,5-
di(benzyloxy-3,4-dihydroxy-3,4-dihydroxyhexanediamide
on solid support (17g)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine (1S,2R)-(–)-cis-1-
amino-2-indanol (301 mg, 2.03 mmol) to give 17g.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(isobutyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-dihydroxy-
3,4-O-isopropylidenehexanediamide on solid support (17a)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine isobutylamine
(200 µL, 2.01 mmol) to give 17a.
General procedure for the preparation of compounds
18a–h and 1
2.3 M HCl in methanol (5.5 mL) was added to the solid
phase from the previous step (17a–h). After stirring for 4 h
at room temperature under an argon atmosphere, the solid
phase was rinsed with CHCl3 (20 mL) and MeOH (10 mL).
The combined organic layer was diluted by 20 mL CHCl3
and extracted with saturated NaHCO3 (2 × 30 mL). The
combined aqueous phases were washed with CHCl3 (2 ×
40 mL). The combined organic layer was dried, concen-
trated, and purified by column chromatography to give
18a–h and 1.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(methyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-dihydroxy-
3,4-O-isopropylidenehexanediamide on solid support (17b)
The solid phase 16 was reacted according to the general
procedure, vide supra, using the amine methylamine in THF
(2 mL, 2 M) to give 17b.
© 2000 NRC Canada

836
Can. J. Chem. Vol. 78, 2000
matography (chloroform–methanol, 40:1). 13C NMR
(CDCl3) δ: 36.6 (CH2-NH), 39.3 (CH2-Ar), 58.0 (CH-NH),
71.6, 71.8, 72.5, 73.6, 74.0, 80.4, 81.3 (CH-OH, 2 OCH2Ph,
C2, C3, C4, and C5), 103.9, 111.6, 124.0, 125.4, 127.1,
128.2, 128.3, 128.5, 128.7, 130.9, 136.5, 136.6, 139.7, 140.8
(aromatic C), 171.6, 172.3 (2 C=O). HRMS calcd. for
646.2491; found 646.2493.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(isobutyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
isopropylidenehexanediamide (18a)
The solid phase 17a was reacted according to the general
procedure, vide supra, to give pure 18a (21 mg, 0.036 mmol,
28% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR
(CDCl3) δ: 20.0 (2 CH3), 28.4 (CH), 39.3 (CH2-Ar), 46.4
(CH2-NH), 58.0 (CH-NH), 71.6, 71.9, 72.6, 73.6, 74.1, 80.5,
81.4 (CH-OH, 2 OCH2Ph, C2, C3, C4, and C5), 124.0,
125.4, 127.0, 128.2, 128.3, 128.5, 128.7, 128.8, 136.7,
139.8, 140.8 (aromatic C), 171.5, 172.3 (2 C=O). HRMS
calcd. for 576.2835; found 576.2829.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(benzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
isopropylidenehexanediamide (18f)
The solid phase 17f was reacted according to the general
procedure, vide supra, to give pure 18f (17 mg, 0.028 mmol,
21% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR (CDCl3)
δ: 39.3 (CH2-Ar), 43.1 (CH2-NH), 57.9 (CH-NH), 71.7,
71.8, 72.5, 73.6, 74.0, 80.4, 81.4 (CH-OH, 2 OCH2Ph, C2,
C3, C4, and C5), 124.1, 125.4, 127.1, 127.6, 128.2, 128.4,
128.7, 130.9, 136.5, 137.5, 139.7, 140.8 (aromatic C), 171 5,
172.3 (2 C=O). HRMS calcd. for 633.3050; found 633.3056.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
(methyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
isopropylidenehexanediamide (18b)
The solid phase 17b was reacted according to the general
procedure, vide supra, to give pure 18b (24 mg, 0.045 mmol,
35% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR (CDCl3)
δ: 25.9 (CH3), 39.3 (CH2-Ar), 58.0 (CH-NH), 71.5, 71.9,
72.6, 73.6, 74.0, 80.7, 81.5 (CH-OH, 2 OCH2Ph, C2, C3,
C4, and C5), 124, 125.4, 127.1, 128.2, 128.4, 128.4, 128.7,
136.6, 139.7, 140.8 (aromatic C), 172.0, 172.3, (2 C=O).
HRMS calcd. for 534.2366, found 534.2359.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2-
methoxybenzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
isopropylidenehexanediamide (18g)
The solid phase 17g was reacted according to the general
procedure, vide supra, to give pure 18g (38 mg, 0.06 mmol,
47% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR (CDCl3)
δ: 39.2, 39.2 (CH2-Ar and CH2-NH), 55.1 (CH3-O), 57.9
(CH-NH), 71.4, 71.8, 72.5, 73.4, 73.8, 80.4, 81.1 (CH-OH, 2
OCH2Ph, C2, C3, C4, and C5), 110.2, 120.6, 124.0, 125.3,
125.5, 126.9, 128.1, 128.2, 128.5, 129.0, 129.5, 136.7,
136.7, 139.9, 140.7, 157.5 (aromatic C), 171.0, 172.2 (2
C=O). HRMS calcd. for 640.2785; found 640.2783.
N1-(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2-
hydroxyethyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
dihydroxyhexanediamide (18c)
The solid phase 17c was reacted according to the general
procedure, vide supra, to give pure 18c (19 mg, 0.034 mmol,
26% based on loading) after purification with column chro-
matography (chloroform–methanol, 20:1). 13C NMR
(CDCl3) δ: 39.3 (CH2-Ar), 41.9 (CH2-NH), 57.6 (CH-NH),
61.1 (CH2-OH), 71.5, 71.6, 72.5, 73.2, 73.3 (CH-OH, 2
OCH2Ph, C2, C3, C4, and C5), 124.0, 125.3, 127.0, 128.1,
128.2, 128.3, 128.6, 136.6, 136.8, 139.8, 140.7 (aromatic
C),171.6 (C=O). HRMS calcd. for 564.2472; found
564.2460.
N1,N6-Di[(2R)-hydroxy-1(S)-indanyl]-(2R,3R,4R,5R)-2,5-
di(benzyloxy-3,4-dihydroxyhexanediamide (1)
The solid phase 17h was reacted according to the general
procedure, vide supra, to give pure 1 (14 mg, 0.021 mmol,
17% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR (CDCl3)
δ: 39.1 (2 CH2-Ar), 57.7 (2 CH-NH), 71.6, 72.5, 73.4, 81.3
(CH-OH, 2 OCH2Ph, C2, C3, C4, and C5), 124.0, 125.3,
126.9, 128.1, 128.2, 128.6, 136.7, 139.8, 140.8 (aromatic C),
171.5 (C=O).
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-
[(1S)-2-methyl-1-(methylcarbamoyl)propyl]-(2R,3R,4R,5R)-
2,5-dibenzyloxy-3,4-O-isopropylidenehexanediamide (18d)
The solid phase 17d was reacted according to the general
procedure, vide supra, to give pure 18d (17 mg, 0.029 mmol,
23% based on loading) after purification with column chro-
matography (chloroform–methanol, 40:1). 13C NMR (CDCl3)
δ: 17.1, 19.6 (CH3-CH); 26.1 (CH3-NH), 29.1 (CH), 39.3
(CH2-Ar); 58.0, 58.4 (CH-NH and O=C-CH-NH), 72.2,
72.4, 72.8, 73.4, 81.3, 81.8 (CH-OH, 2 OCH2Ph, C2, C3,
C4, and C5), 123.9, 125.4, 127.0, 128.1, 128.2, 128.4, 128.5,
128.7, 128.7, 136.4, 139.6, 140.8 (aromatic C), 170.9, 172.0
(2 C=O). HRMS calcd. for 610.2679; found 610.2673.
Conclusions
A solid phase parallel synthesis of unsymmetrical inhibi-
tors has been developed which will aid further development
and combinatorial amplification. A number of new potent in-
hibitors were discovered.
N1-[(1R,2S)-2-Hydroxy-2,3-dihydro-1H-indenyl]-N6-(2,4-
difluorobenzyl)-(2R,3R,4R,5R)-2,5-dibenzyloxy-3,4-O-
isopropylidenehexanediamide (18e)
The solid phase 17e was reacted according to the general
procedure, vide supra, to give pure 18e (14 mg, 0.020 mmol
17% based on loading) after purification with column chro-
Acknowledgment
We gratefully acknowledge support from the Swedish Na-
tional Board for Technical Development (NUTEK) and from
Medivir AB, Huddinge, Sweden and Dr. Karl-Erik Karlsson
Hässle AB for HRMS.
© 2000 NRC Canada

Oscarsson et al.
837
17. A.K. Ghosh, S. Fidanze, and C.H. Senanayake. Synthesis, 937
(1998).
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© 2000 NRC Canada