A general synthetic approach to novel conformationally restricted arginine side chain mimetics

Article abstract of DOI:10.1016/S0040-4020(01)01243-1

A general synthesis of several novel partially saturated, conformationally restricted heterobicyclic arginine side chain mimetics is described. These compounds are interesting peptidomimetic building blocks for incorporation into trypsin-like serine protease inhibitors.

Full text of DOI:10.1016/S0040-4020(01)01243-1

TETRAHEDRON
Pergamon
Tetrahedron 58 /2002) 1557±1563
A general synthetic approach to novel conformationally restricted
arginine side chain mimetics
p
Lucija Peterlin-Ma sÏ i cÏ , Andreja Jurca, Petra Marinko, Anita Jan cÏ ar and Danijel Kikelj
Faculty of Pharmacy, University of Ljubljana, A sÏ ker cÏ eva 7, 1000 Ljubljana, Slovenia
Received 29 August 2001;revised 16 November 2001;accepted 13 December 2001
AbstractÐA general synthesis of several novel partially saturated, conformationally restricted heterobicyclic arginine side chain mimetics
is described. These compounds are interesting peptidomimetic building blocks for incorporation into trypsin-like serine protease inhibitors.
q 2002 Elsevier Science Ltd. All rights reserved.
1
. Introduction
which were incorporated as isosteric replacements for
the arginine moiety into tripeptidomimetic thrombin
inhibitors.
1
0
Trypsin-like serine proteases that are involved in many
biological processes /e.g. blood coagulation) cleave a poly-
peptide chain after the basic amino acids arginine /I) and
lysine. The basic side chains of these amino acids interact
via hydrogen bonding and ionic interactions with an aspartic
acid residue at the bottom of the S pocket of the enzyme.
1
Arginine residue /I) or mimetics thereof are, consequently,
common groups that have been incorporated into the P
2. Results and discussion
1
,2
In this paper we report a general synthesis of novel partially
saturated, heterobicyclic arginine side chain mimetics III
containing a ®ve- or six-membered N-heterocyclic ring
optionally substituted by amino or guanidino groups /Fig.
1). The cyclohexane ring, which mimics the arginine
methylene side chain, introduces conformational rigidity
into the molecule. These compounds are interesting
mimetics of the arginine side chain, which can be easily
functionalised via the nucleophilic aminomethyl group.
When incorporated into potential tripeptidomimetic
thrombin inhibitors, the bulky cyclohexane ring of III
could confer selectivity for inhibition of thrombin vs tryp-
sin. Additionally, the aminomethyl group bound to the
cyclohexane ring of III gives to the inhibitors more
1
3
±8
position of many thrombin inhibitors.
It has been
shown that bioavailability and selectivity of an inhibitor
for speci®c serine-proteases can be conferred based on the
structure and basicity of the moiety incorporated into the P
position. Thus, signi®cant effort has been focused on the
design and preparation of arginine mimetics and arginine
side chain mimetics that could confer selective inhibition
for speci®c serine proteases and, in addition possess reduced
basicity. To this end, we designed and described in a
preliminary communication several novel conformation-
ally restricted heterocyclic arginine side chain mimetics,
1
3
±8
9
a
9
b
Figure 1.
Keywords: heterocycles;arginine mimetics;peptidomimetics;serine proteases;thrombin inhibitors.
Corresponding author. Tel.: 1386-1-4769-561;fax: 1386-1-4258-031;e-mail: danijel.kikelj@ffa.uni-lj.si
p
0040±4020ꢀ02ꢀ$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020/01)01243-1

1558
L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
Scheme 1.
conformational freedom as compared to the inhibitors
containing similar arginine side-chain mimetics with
/Scheme 2) started with the preparation of 1,4-dioxaspiro
[4.5]dec-8-ylmethanamine /3) by reductive cyanation of
1,4-cyclohexanedione monoethylene acetal /1) with tosyl-
methyl isocyanide and subsequent reduction of the nitrile 2
1
1
amino group bound directly to the cyclohexane ring.
Although several heterocyclic amines have recently been
1
2±15
16
used as arginine mimetics,
partially saturated amino-
with lithium aluminum hydride. After protecting the
methyl substituted heterobicycles III have not so far been
described. A general synthetic approach to conformation-
ally restricted heterocyclic arginine side chain mimetics
with general structure III is, therefore, highly desirable.
amino group of 3 by acetylation, cleavage of the 1,3-
dioxolane ring with 90% formic acid gave N-[/4-oxocyclo-
hexyl)methyl] acetamide /5). The ketone 5 was converted
by condensation with DMFDMA into novel enamino
ketone 6 and by bromination into novel bromo ketone 7,
which were found as useful intermediates for further trans-
formations into different heterocyclic compounds III.
1
7
Different heterocyclic arginine side chain mimetics pre-
pared as a part of this study are listed in Scheme 1. A general
approach to afford arginine side chain mimetics 13±17, 19
and 20 includes the synthesis of ketone 5, which was trans-
formed by condensation with dimethylformamide dimethyl
acetal /DMFDMA) or by bromination to the key intermedi-
ates enamino ketone 6 or bromo ketone 7 /Scheme 2).
Ketones 6 and 7 are useful intermediates for further trans-
formations with different bifunctional nucleophiles into
different heterocyclic compounds III. Enamino ketone 6
could be easily transformed by cyclocondensation with
different nucleophiles and subsequent hydrolysis to the
bicyclic heterocycles 13±17 /Scheme 3), whereas cyclo-
condensation of the bromo ketone 7 afforded bicyclic
heterocycles 19 and 20 /Scheme 4).
The preparation of arginine side chain mimetics 13±17
is depicted in Scheme 3. The reaction of the enamino
ketone 6 with guanidine hydrochloride in the presence
of sodium ethoxide in dry ethanol, followed by hydroly-
sis of the resulting tetrahydroquinazoline derivative 8
with aqueous sodium hydroxide in methanol gave 6-
/aminomethyl)-5,6,7,8-tetrahydro-2-quinazolinamine /13)
in 66% yield. Facile cyclocondensation of 6 with
hydrazine hydrate or N-methylhydrazine in ethanol gave
tetrahydroindazole derivative
9 in 74% yield and
methyltetrahydroindazole derivative 10 in 51% yield,
respectively. Final hydrolysis of acetamides 9 and 10
with 6 M hydrochloric acid gave 4,5,6,7-tetrahydro-2H-
indazol-5-ylmethanamine dihydrochloride /14) in 96%
The synthesis of enamino ketone 6 and bromo ketone 7

L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
1559
Scheme 2. /a) TOSMIC, t-BuOKꢀDME, 08C, 1 h, then rt, 2 h;/b) LiAlH
DMFDMA, Et N, toluene, re¯ux, 7 h;/f) Br , CH Cl , 408C, 30 min.
4 2
ꢀTHF, re¯ux, 2 h, then rt, 12 h;/c) Ac O, rt, 1 h;/d) 90% HCOOH, rt, 16 h;/e)
3
2
2
2
Scheme 3. /a) Guanidine hydrochlorideꢀNaOEt, abs. EtOH, re¯ux, 3 h;/b) NH
KOH, abs. EtOH, re¯ux, 2 h;/ii) Ac O, re¯ux, 1 h;/e) formamidine hydrochlorideꢀNaOEt, abs. EtOH, re¯ux 4 h;/f), /i), /j) aq. NaOH, MeOH, re¯ux, 16 h;
g), /h) 6 M HCl, re¯ux, 6 h.
2 2 2 2 3
NH ´H O, EtOH, rt, 16 h;/c) NH NHCH , EtOH, rt, 16 h;/d) /i) glycine,
2
/
Scheme 4. /a) Thiourea, EtOH, re¯ux 2 h;/b) amidinothiourea, EtOH, re¯ux, 16 h;/c) 47% HBr, re¯ux, 16 h.

1560
L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
yield and 2-methyl-4,5,6,7-tetrahydro-2H-indazol-5-yl)
methanamine hydrochloride /15) in 82% yield.
standard. IR spectra were obtained on a Perkin±Elmer
1600 FT-IR spectrometer. Microanalyses were performed
on a Perkin±Elmer C, H, N analyzer 240 C. Elemental
analyses for C, H, N were within ^0.4% of the calculated
values. Mass spectra were obtained using a VG-Analytical
Autospec Q mass spectrometer.
Base-catalyzed reaction of 6 with glycine, performed by
1
8
analogy to a previously published procedure, afforded a
potassium-salt adduct, which on treatment with acetic anhy-
dride was cyclized, decarboxylated, and acetylated to give
the diamide 11. After puri®cation by column chromato-
graphy, the compound 11, which eluted from the column
in the later fractions, was obtained in low /18%) yield. Basic
hydrolysis of 11 with aqueous sodium hydroxide in
methanol produced 4,5,6,7-tetrahydro-2H-isoindol-5-yl-
methanamine /16) in 74% yield. 6-/Aminomethyl)-5,6,7,8-
tetrahydroquinazoline /17) was prepared by cyclocondensa-
tion of the enamino ketone 6 and formamidine hydro-
chloride in the presence of sodium ethoxide in dry ethanol
and subsequent basic hydrolysis.
4.1.1. 1,4-Dioxaspiro[4.5]decane-8-carbonitrile ꢀ2). To a
cooled /2108C) suspension of 1,4-cyclohexanedione mono-
ethylene acetal /1) /15.0 g, 0.096 mol) and tosylmethyliso-
cyanide /24.5 g, 0.125 mol) in DME /300 mL) containing
abs. EtOH /10 mL) was added t-BuOK /25.0 g, 0.221 mol)
portionwise over the course of 0.5 h so that the temperature
was maintained at ,58C. After the addition was completed,
the reaction was stirred for 1 h at 08C and then for 2 h at rt.
The mixture was concentrated to an orange-brown solid;
water /100 mL) was added to the residue and extracted
with Et O /5£70 mL). The combined extracts were washed
2
The condensation of the bromo ketone 7 with bifunctional
nucleophiles leading to compounds 18±20 is shown in
Scheme 4. The reaction of 7 with thiourea and amidino-
thiourea produced amino-substituted tetrahydrobenzo-
thiazole 18 in 52% yield and guanidino-substituted
tetrahydrobenzothiazole 19 in 39% yield, respectively.
Deprotection of the acetamido group of 18 in 47% HBr
under re¯ux yielded 6-/aminomethyl)-4,5,6,7-tetrahydro-
with brine /3£50 mL) and dried /Na SO ). Concentration
2
4
under reduced pressure gave a yellow oil which was puri®ed
by distillation through a 10 cm Vigreux column to give 2 as
1
6
a colourless oil: bp 958C, 0.6 Torr;lit: 94±95 8C, 1 Torr;
yield: 11.5 g /72%). IR /KBr): n 3534, 2954, 2885, 2239,
1693, 1625, 1448, 1373, 1336, 1231, 1103, 1033, 936 cm .
2
1
1
1
MS /FAB): mꢀz /%) 168 /MH , 92), 154 /100). H NMR
/300 MHz, CDCl ): dˆ1.57±1.67 /m, 2H, 7-H, 9-H), 1.79±
3
1,3-benzothiazol-2-amine /20) as a hydrobromide salt in
70% yield. Deprotection of the guanidino substituted
1.90 /m, 2H, 7-H, 9-H), 1.90±2.04 /m, 4H, 6-H, 10-H),
2.61±2.70 /m, 1H, 8-H), 3.95 /s, 4H, 2-H, 3-H).
tetrahydrobenzothiazole 19 by acid hydrolysis using
aqueous hydrochloric or hydrobromic acid with several
modi®cations of the reaction conditions, including time,
solvent and concentration of acid, were unsuccessful, due
to the destruction of the guanidino-substituted heterocycle
as indicated by mass spectra and proton nuclear magnetic
resonance.
4.1.2. 1,4-Dioxaspiro[4.5]dec-8-ylmethanamine ꢀ3). To an
ice-bath-cooled 1 M solution of LiAlH in THF /141 mL,
4
0.141 mol), nitrile 2 /15.7 g, 0.094 mol) was added drop-
wise over 1 h. After the addition was complete, the solution
was heated to re¯ux for 2 h and then stirred at rt for 12 h.
The reaction mixture was quenched by careful sequential
addition of H O /5.6 mL), 15% NaOH /5.6 mL), and H O
2
2
/15.7 mL). The initial H O portion was diluted with THF to
2
3
. Conclusion
aid addition and moderate the quench. The resulting precipi-
tate was collected by ®ltration. Concentration under reduced
pressure and distillation of the resulting oil gave 3 as colour-
To summarize, we have succeeded in preparing novel
partially saturated, conformationally restricted hetero-
bicyclic arginine side chain mimetics 13±17, 19 and 20.
These compounds are interesting building blocks for incor-
poration into various serine protease inhibitors.
1
6
less oil: bp 728C, 0.3 Torr;lit: 110±111 8C, 3 Torr; yield:
12.3 g /77%). IR /KBr): n 3364, 2934, 1669, 1558, 1448,
1375, 1338, 1104, 1034, 929 cm . MS /FAB): mꢀz /%) 172
2
1
1
1
/MH , 100). H NMR /300 MHz, CDCl
2
2
): dˆ1.04 /br s,
3
H, NH ), 1.14±1.40 /m, 3H, 7-H, 8-H, 9-H), 1.46±1.59 /m,
2
H, 7-H, 9-H), 1.71±1.80 /m, 4H, 6-H, 10-H), 2.55 /d, 2H,
), 3.92 /s, 4H, 2-H, 3-H).
2
4
. Experimental
Jˆ6.02 Hz, CH
4
.1. General
4.1.3. N-ꢀ1,4-Dioxaspiro[4.5]dec-8-ylmethyl)acetamide
ꢀ4). A solution of 1,4-dioxaspiro[4.5]dec-8-ylmethylamine
Chemicals were purchased from Aldrich Chemical Co. and
Fluka and used without further puri®cation. THF was kept
over sodium and distilled immediately prior to use. Analy-
tical TLC was performed on Merck silica gel /60 F 254)
plates /0.25 mm). Visualization was effected with ultra-
violet light or any of the following reagents: ninhydrin
and 2,4-dinitrophenylhydrazine. Column chromatography
/3) /12.3 g, 0.072 mol) in an excess of acetic anhydride
/70 mL) was stirred at rt for 1 h. The excess acetic anhy-
dride was removed under reduced pressure. Water /50 mL)
was added, and the mixture was extracted with CH
/3£40 mL). The organic extracts were washed with brine
SO ), and evaporated under reduced
Cl
2
2
/3£40 mL), dried /Na
2
4
pressure to give 4 as yellow oil;yield: 12.3 g /80%). IR
/KBr): n 3297, 3094, 2937, 2884, 1734, 1651, 1556,
1446, 1230, 1155, 1099, 1034, 915 cm . MS /FAB): mꢀz
w
was carried out on Florisil /particle size 100±200 mesh)
and silica gel 60 /particle size 240±400 mesh). Melting
2
1
1
1
points were determined on
a
Reichert hot stage
/%) 214 /MH , 100). H NMR /300 MHz, CDCl ):
3
1
microscope and are uncorrected. H NMR spectra were
recorded on a Bruker AVANCE DPX300 spectrometer in
CDCl3 or DMSO solution with TMS as the internal
dˆ1.18±1.33 /m, 2H, 7-H, 9-H), 1.44±1.57 /m, 3H, 7-H,
8-H, 9-H), 1.68±1.78 /m, 4H, 6-H, 10-H), 1.97 /s, 3H,
COCH
), 3.12 /t, 2H, Jˆ6.36 Hz, CH
), 3.96 /s, 4H, 2-H,
2
3

L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
1561
3
6
-H), 5.68 /br s, 1H, NH). Anal. Calcd for C H NO : C,
1
1.97;H, 8.92;N, 6.57. Found: C, 61.78;H, 8.87;N, 6.39.
0.75 g /76%);mp 205±208 8C. IR /KBr): n 3304, 3084,
2944, 2859, 1674, 1649, 1602, 1560, 1493, 1421, 1376,
1
19
3
2
265, 1211, 1096, 960, 786 cm . MS /EI): mꢀz /%) 220
1
1
/M , 34), 148 /100). H NMR /300 MHz, CDCl3):
1
1
4
.1.4. N-[ꢀ4-Oxocyclohexyl)methyl]acetamide ꢀ5). A solu-
tion of N-/1,4-dioxaspiro[4.5]dec-8-ylmethyl)acetamide /4)
12.3 g, 0.058 mol) in 90% formic acid /120 mL) was
stirred at rt for 16 h. The excess formic acid was removed
under reduced pressure. Water /30 mL) and aq. NaHCO3
dˆ1.41±1.55 /m, 1H, 6-H), 1.88±2.03 /m, 2H, 7-H), 2.04
/
/s, 3H, COCH ), 2.26±2.34, 2.66±2.78 /2£m, 4H, 5-H, 8-H),
3
3.31 /t, 2H, Jˆ6.78 Hz, CH ), 4.83 /s, 2H, 2-NH ), 5.60 /br s,
2
2
1H, NHCO), 8.02 /s, 1H, 4-H). Anal. Calcd for C H N O:
4
11
16
/
40 mL) were added, and the mixture was extracted with
C, 60.00;H, 7.27;N, 25.45. Found: C, 59.76;H, 7.06;N,
25.21.
CH Cl2 /5£30 mL). The organic extracts were washed
2
with aq. NaCl /3£30 mL), dried /Na SO ), and evaporated
2
4
under reduced pressure to give 5 as a white solid;yield:
4.1.8. ꢀ^)-N-ꢀ4,5,6,7-Tetrahydro-2H-indazol-5-ylmethyl)-
acetamide ꢀ9). A solution of the enamino ketone 6 /1.0 g,
4.46 mmol) and NH NH ´H O /0.25 mL, 5.0 mmol) in
7
1
.5 g /77%);mp 51±54 8C. IR /KBr): n 3276, 3092, 2940,
715, 1654, 1560, 1437, 1368, 1298, 1167, 1118, 998, 784,
2
2
2
2
10, 497 cm . MS /EI): mꢀz /%) 169 /M , 45), 110 /100).
1
1
6
MeOH /20 mL) was stirred at rt for 16 h. The solvent
was evaporated and the product was puri®ed by column
chromatography on Florisil using EtOAcꢀMeOH /2:1) as
1
H NMR /300 MHz, CDCl ): dˆ1.35±1.51 /m, 2H, 2-H, 6-
3
w
H), 2.01 /s, 3H, COCH ), 2.02±2.11 /m, 3H, 1-H, 2-H, 6-H),
3
2
CH ), 5.77 /br s, 1H, NH). Anal. Calcd for C H NO : C,
.26±2.48 /m, 4H, 3-H, 5-H), 3.21 /t, 2H, Jˆ6.41 Hz, 7-
eluant to yield 9 as a white solid;yield: 0.56 g /65%);mp
129±1328C. IR /KBr): n 3261, 2928, 1652, 1558, 1437,
1368, 1293, 1088, 1035, 962, 782, 605 cm . MS /EI):
2
9
15
2
2
1
6
3.91;H, 8.88;N, 8.28. Found: C, 63.85;H, 8.71;N, 8.02.
1
1
mꢀz /%) 193 /M , 36), 121 /100). H NMR /300 MHz,
CDCl ): dˆ1.49±1.60 /m, 1H, 5-H), 1.89±1.95 /m, 2H,
4
.1.5. ꢀ^)-N-ꢀ{3-[ꢀDimethylamino)methylidene]-4-oxo-
3
cyclohexyl}methyl)acetamide ꢀ6). A solution of N-[/4-
oxocyclohexyl)methyl]acetamide /5) /5.0 g, 0.03 mol),
DMFDMA /35 mL, 0.26 mol), and Et N /0.6 mL) in toluene
6-H), 2.02 /s, 3H, COCH ), 2.18±2.28, 2.58±2.89 /2£m,
3
4H, 4-H, 7-H), 3.22±3.40 /m, 2H, CH ), 5.61 /br s, 1H,
2
NHCO), 7.31 /s, 1H, 3-H), 10.0±14.0 /very broad s, 1H,
NH). Anal. Calcd for C H N O: C, 62.18;H, 7.77;N,
21.76. Found: C, 61.88;H, 7.85;N, 21.44.
3
/
160 mL) was distilled over a period of 2 h to about one-half
1
0
15
3
the original volume. Toluene /80 mL) was then added to the
residue, and the mixture was maintained just below the
boiling point for 2 h. Distillation was continued to a volume
one-half of the original during 1.5 h. Toluene /80 mL) was
again added, and the process was repeated a third and fourth
time. Volatiles were distilled, and the product was puri®ed
4.1.9. ꢀ^)-N-[ꢀ2-Methyl-4,5,6,7-tetrahydro-2H-indazol-
5-yl)methyl]acetamide ꢀ10). A solution of the enamino
ketone 6 /0.80 g, 3.57 mmol) and N-methylhydrazine
/0.19 mL, 3.57 mmol) in MeOH /15 mL) was stirred at rt
for 16 h. The solvent was evaporated, and the product was
w
by column chromatography on 120 g of Florisil using
CH Cl ꢀMeOH /95:5) as eluant to yield 6 as a yellow oil;
yield: 4.5 g /66%). IR /KBr): n 3278, 2929, 1637, 1540,
w
puri®ed by column chromatography on Florisil using
CH Cl ꢀMeOH /2:1) as eluant to yield 10 as a yellow
2
2
2
2
2
420, 1333, 1202, 1128, 1010 cm . MS /EI): mꢀz /%)
1
1
2
solid;yield: 0.38 g /51%);mp 121±124 8C. IR /KBr): n
3323, 1641, 1540, 1476, 1378, 1279, 1181, 1014,
1
1
24 /M , 55), 152 /100). H NMR /300 MHz, CDCl ):
3
2
787 cm . MS /EI): mꢀz /%) 207 /M , 56), 35 /100). H
1
1
1
dˆ1.38±1.50 /m, 1H, 1-H), 1.73±1.83, 1.84±1.93 /2£m,
2
2
3
H, 6-H), 2.01 /s, 3H, COCH ), 2.01±2.35, 2.37±2.43,
3
NMR /300 MHz, CDCl ): dˆ1.42±1.55 /m, 1H, 5-H),
3
.45±2.49, 2.82±2.86, 2.87±2.91 /5£m, 4H, 2-H, 5-H),
1.84±1.96 /m, 2H, 6-H), 1.99 /s, 3H, COCH ), 2.13±2.24,
3
.09 /s, 6H, N/CH ) ), 3.11±3.20, 2.33±3.33 /2£m, 2H, 7-
2.55±2.86 /2£m, 4H, 4-H, 7-H), 3.28 /t, 2H, Jˆ6.4 Hz,
3
2
H), 5.85 /br s, 1H, NHCO), 7.49 /m, 1H, CH±methylidene).
Anal. Calcd for C H N O : C, 64.29;H, 8.93;N, 12.50.
Found: C, 63.95;H, 8.89;N, 12.39.
CH ), 3.81 /s, 3H, 2-CH ), 5.77 /br s, 1H, NH), 7.03 /s,
2
3
1H, 3-H). Anal. Calcd for C H N O: C, 63.74;H, 8.27;
11 17
1
2
20
2
2
3
N, 20.27. Found: C, 63.61;H, 8.45;N, 20.45.
4
.1.6.
ꢀ^)-N-[ꢀ3-Bromo-4-oxocyclohexyl)methyl]acet-
amide ꢀ7). A freshly prepared solution of Br /0.876 g,
4.1.10. ꢀ^)-N-[ꢀ2-Acetyl-4,5,6,7-tetrahydro-2H-isoindol-
5-yl)methyl]acetamide ꢀ11). The compound was prepared
in analogy to procedure described in Ref. 18. To a solution of
glycine /0.74 g, 9.91 mmol), and KOH /0.56 g, 9.91 mmol)
in abs. EtOH /33 mL) was added enamino ketone 6 /2.0 g,
9.91 mmol). The resulting mixture was heated under re¯ux
for 2 h and then diluted with ether. The potassium salt was
2
5
.5 mmol) in CH Cl /19.0 mL) was added dropwise over
2 2
a 1 h period, to a stirred solution of N-[/4-oxocyclohexyl)-
methyl]acetamide /5) /0.930 g, 5.5 mmol) in CH Cl
2
2
/
10 mL). The reaction mixture was then re¯uxed for 1 h,
the solvent was removed under reduced pressure to obtain
a brown foam, which was used further without puri®cation.
®ltered off and treated with Ac O /33 mL). The solution was
2
then re¯uxed for 1 h and the excess Ac O removed under
2
4
.1.7. ꢀ^)-N-[ꢀ2-Amino-5,6,7,8-tetrahydro-6-quinazolinyl)-
methyl]acetamide ꢀ8). To a solution of sodium ethoxide
0.1 g, 4.46 mmol) in abs. EtOH /20 mL), guanidine hydro-
chloride /0.43 g, 4.46 mmol) was added. After stirring for
.5 h, a solution of N-/{3-[/dimethylamino)methylidene]-
-oxocyclohexyl}methyl) acetamide /6) /1.0 g, 4.46 mmol)
reduced pressure. The residue was puri®ed by column
chromatography /Kieselgel 60, 0.40±0.063 mm, CH Cl ꢀ
2
2
/
MeOH /9:1)) to obtain 11 as a yellow solid;yield: 0.41 g
/18%);mp 90±93 8C. IR /KBr): n 3304, 2926, 1726, 1645,
1547, 1406, 1327, 1216, 1068, 940, 784, 621 cm . MS
2
1
0
4
1
1
/FAB): mꢀz /%) 235 /MH , 100). H NMR /300 MHz,
CDCl ): dˆ1.35±1.47 /m, 1H, 5-H), 1.82±1.96 /m, 2H, 6-
in abs. EtOH was added and the reaction mixture was
re¯uxed under argon for 3 h. The separated solid was
collected by ®ltration to give 8 as a white solid;yield:
3
H), 2.03 /s, 3H, COCH ) 2.15±2.27, 2.50±2.58, 2.67±2.79
3
/3£m, 4H, 4-H, 7-H), 2.47 /s, 3H, 2-COCH ), 3.21±3.38
3

1562
L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
/m, 2H, CH ), 5.56 /br s, 1H, NHCO), 6.99 /br s, 2H, 1-H, 3-
H). Anal. Calcd for C H N O : C, 66.64;H, 7.74;N,
IR /KBr): n 3434, 2900, 1627, 1515, 1460, 1400, 1179,
1
1073, 1021, 923, 856, 807 cm . MS /EI): mꢀz /%) 166
/M , 75), 148 /100). H NMR /300 MHz, DMSO-d ):
6
2
2
1
3
18
2
2
1
1
1
1.96. Found: C, 66.82;H, 7.60;N, 12.22.
dˆ1.35±1.48 /m, 1H, 5-H), 1.89±2.03 /m, 2H, 6-H),
2.13±2.22, 2.56±2.63 /2£m, 4H, 4-H, 7-H), 2.75±2.85
/m, 2H, CH ), 3.74 /s, 3H, 2-CH ), 7.40 /s, 1H, 3-H), 8.03
/br s, 3H, NH ). Anal. Calcd for C H ClN : C, 56.33;H,
3 9 16 3
8.34;N, 21.90. Found: C, 56.01;H, 8.16;N, 21.69.
4
.1.11. ꢀ^)-N-[ꢀ5,6,7,8-tetrahydro-6-quinazolinyl)methyl]-
acetamide ꢀ12). To a solution of sodium ethoxide /40 g,
.74 mmol) in abs. EtOH /20 mL), formamidine hydro-
chloride /0.14 g, 1.74 mmol) was added. After stirring for
.5 h, a solution of enamino ketone 6 /0.3 g, 1.34 mmol) in
2
3
1
1
0
abs. EtOH was added and the reaction mixture was re¯uxed
under argon for 4 h. The solvent was evaporated under
reduced pressure and the residue was puri®ed by column
chromatography /Kieselgel 60, 0.40±0.063 mm, CH Cl ꢀ
4.1.15. ꢀ^)-4,5,6,7-Tetrahydro-2H-isoindol-5-ylmethan-
amine ꢀ16). A solution of the diamide 11 /42 mg,
0.179 mmol), NaOH /3.0 g), H O /3 mL), and MeOH
2
/12 mL) was re¯uxed for 16 h. Water /10 mL) was added
and the mixture was extracted with CH Cl /4£20 mL). The
2
2
MeOH /9:1)) to obtain 12 as a white solid;yield: 0.23 g
/
2
2
83%);mp 105±108 8C. IR /KBr): n 3283, 2920, 1693,
organic extracts were washed with brine /3£20 mL), dried
2
558, 1458, 1401, 1306, 1046 cm . MS /FAB): mꢀz /%)
1
1
2
1
/Na SO ) and evaporated under reduced pressure to yield 16
2
4
1
1
06 /MH , 100). H NMR /300 MHz, CDCl ): dˆ1.50±
as an orange solid;yield: 20 mg /74%);mp 87±90 8C. IR
/KBr): n 3362, 2916, 1629, 1570, 1441, 1204, 1061, 922,
3
.64 /m, 1H, 6-H), 1.97±2.14 /m, 2H, 7-H), 2.05 /s, 3H,
2
1
1
1
COCH ), 2.42±2.54, 2.82±3.07 /2£m, 4H, 5-H, 8-H), 3.34
769, 601 cm . MS /FAB): mꢀz /%) 151 /MH , 100). H
NMR /300 MHz, CDCl3): dˆ1.36±1.48 /m, 5-H,
NH 1H O), 1.69±1.79 /m, 1H, 6-H), 1.92±2.02 /m, 1H,
3
/
1
t, 2H, Jˆ6.78 Hz, CH ), 5.70 /br s, 1H, NHCO), 8.42 /s,
2
H, 4-H), 8.95 /s, 1H, 2-H). Anal. Calcd for C H N O: C,
11 15 3
2
2
6
4.37;H, 7.37;N, 20.47. Found: C, 64.03;H, 7.22;N, 20.15.
6-H), 2.18±2.28, 2.53±2.65, 2.70±2.86 /3£m, 6H, 4-H, 7-
H, CH ), 6.51 /s, 1H, CH), 6.52 /s, 1H, CH), 7.95 /m, 1H,
2
4
.1.12. ꢀ^)-6-ꢀAminomethyl)-5,6,7,8-tetrahydro-2-quin-
NH-exchange). Anal. Calcd for C H N : C, 71.96;H, 9.39;
2
9
14
azolinamine ꢀ13). A solution of N-[/2-amino-5,6,7,8-tetra-
hydro-6-quinazolinyl)methyl]acetamide /8) /0.7 g, 3.18 mmol)
and NaOH /15 g, 0.38 mol) in a mixture of H O /20 mL)
N, 18.65. Found: C, 72.05;H, 9.32;N, 18.28.
4.1.16. ꢀ^)-6-ꢀAminomethyl)-5,6,7,8-tetrahydroquinazo-
line ꢀ17). A solution of N-[/5,6,7,8-tetrahydro-6-quinazo-
linyl)methyl]acetamide /12) /0.13 g, 0.63 mmol) and
2
and MeOH /30 mL) was re¯uxed for 16 h. Water /20 mL)
was added, and the mixture was extracted with CH Cl
2
2
/
3£20 mL). The organic extracts were washed with brine
NaOH /9 g, 0.225 mol) in a mixture of H O /12 mL) and
2
/3£20 mL), dried /Na SO ), and evaporated under reduced
pressure to give 13 as a white solid;yield: 0.34 g /60%);mp
MeOH /18 mL) was re¯uxed for 16 h. Water /20 mL) was
added, and the mixture was extracted with CH Cl
2
4
2
2
1
1
5
52±1558C. IR/KBr): n 3315, 3142, 2927, 2855, 1648,
590, 1557, 1473, 1424, 1197, 964, 861, 808, 593,
01 cm . MS /EI): mꢀz /%) 178 /M , 40), 161 /100). H
/3£20 mL). The organic extracts were washed with brine
/3£20 mL), dried /Na SO ), and evaporated under reduced
2
4
2
1
1
1
pressure to give 17 as a white solid;yield: 84 mg /84%);mp
88±918C. IR /KBr): n 3350, 2928, 1580, 1454, 1396, 1324,
1164, 936, 730 cm . MS /EI): mꢀz /%) 163 /M , 14), 134
NMR /300 MHz, CDCl ): dˆ1.12±1.43 /br s, 2H, NH ),
3
2
2
1
1
1
2
8
.40±1.55 /m, 1H, 6-H), 1.68±1.82 /m, 1H, 7-H), 2.00±
.10 /m, 1H, 7-H), 2.22±2.33, 2.69±2.81 /2£m, 6H, 5-H,
-H, CH ), 4.85 /s, 2H, 2-NH ), 8.03 /s, 1H, 4-H). Anal.
1
/100). H NMR /300 MHz, CDCl ): dˆ1.44 /br s,
3
NH 1H O), 1.48±1.61 /m, 1H, 6-H), 1.76±1.89 /m, 1H,
2
2
2
2
Calcd for C H N : C, 60.67;H, 7.87;N, 31.46. Found: C,
9
7-H), 2.06±2.17 /m, 1H, 7-H), 2.41±2.51 /dd, 1H,
Jˆ10.55 Hz, CH), 2.77 /d, 2H, Jˆ6.78 Hz, CH ), 2.84±
14
4
6
0.35;H, 7.81;N, 31.25.
2
3
.06 /m, 3H, CH, CH ), 8.42 /s, 1H, 4-CH), 8.93 /s, 1H,
2
4
.1.13. ꢀ^)-4,5,6,7-Tetrahydro-2H-indazol-5-ylmethan-
2-CH). Anal. Calcd for C H N : C, 66.23;H, 8.03;N,
9 13 3
amine dihydrochloride ꢀ14). A solution of the amide 9
0.43 g, 2.23 mmol) in 6 M HCl /25 mL) was heated
25.74. Found: C, 65.92;H, 7.91;N, 25.45.
/
under re¯ux for 6 h. It was then concentrated, and the
product was crystallized from EtOH /10 mL) to yield 14
as a crystalline solid;yield: 0.48 g /96%);mp 289±292 8C.
IR /KBr): n 3408, 2945, 1975, 1611, 1532, 1472, 1290,
4.1.17. ꢀ^)-N-[ꢀ2-Amino-4,5,6,7-tetrahydro-1,3-benzo-
thiazol-6-yl)methyl]acetamide ꢀ18). To a solution of
bromo ketone 7 /0.992 g, 4.0 mmol) in abs. EtOH
/20 mL) thiourea /0.396 g, 5.2 mmol) was added and the
mixture was heated under re¯ux for 2 h. The solvent was
removed under reduced pressure. Water /20 mL) was added
to the residue, the solution was made alkaline with 1 M
NaOH to pH 12 and the mixture extracted with EtOAc
/3£10 mL). The organic extracts were washed with aq.
NaCl /3£10 mL), dried /Na SO ) and evaporated under
2
1
1
232, 858, 757, 644 cm . MS /FAB): mꢀz /%) 152
1
1
/
MH , 100). H NMR /300 MHz, DMSO-d ): dˆ1.41±
6
1
2
4
.56 /m, 1H, 5-H), 1.97±2.08 /m, 2H, 6-H), 2.19±2.30,
.57±2.79, /2£m, 4H, 4-H, 7-H), 2.80±2.87 /m, 2H, CH ),
2
1
3
1
.39 /br s, NH 1H O), 7.78 /d, 1H, Jˆ2.64 Hz, 3-H), 8.23
2
/
m, 1H, NH -exchange). Anal. Calcd for C H Cl N : C,
8
2
15
2
3
2
4
4
2.86;H, 6.70;N, 18.75. Found: C, 42.61;H, 6.68;N, 18.62.
reduced pressure. The product was puri®ed by column
chromatography /Kieselgel 60, EtOAcꢀMeOH /7:1)) to
obtain 18 as a slightly yellow solid;yield 0.38 g /52%);
mp 187±1898C. IR /KBr): n 3440, 3314, 3080, 2928,
1618, 1534, 1474, 1365, 1315, 1254, 1096, 707,
4
.1.14. ꢀ^)-2-Methyl-4,5,6,7-tetrahydro-2H-indazol-5-
yl)methanamine hydrochloride ꢀ15). A solution of the
amide 11 /0.25 g, 1.21 mmol) in 6 M HCl /18 mL) was
heated under re¯ux for 6 h. It was then concentrated, and
the product was crystallized from EtOH /10 mL) to yield 15
as a crystalline solid;yield: 0.20 g /82%);mp 195±197 8C.
2
1
1
1
598 cm . MS /FAB): mꢀz /%) 226 /MH , 100). H NMR
/300 MHz, DMSO-d ): dˆ1.29±1.43 /m, 1H, 6-H), 1.75±
6
1.90 /m, 2H, 5-H), 1.82 /s, 3H, COCH ), 2.08±2.20, 2.26±
3

L. Peterlin-Ma sÏ i cÏ et al. / Tetrahedron 58 *2002) 1557±1563
1563
2
.44, 2.55±2.61 /3£m, 4H, 4-H, 7-H), 3.04 /t, 2H,
References
Jˆ6.41 Hz, CH ), 6.57 /s, 2H, 2-NH ), 7.86 /br t, 1H,
2
2
NHCO). Anal. Calcd for C H N OS: C, 53.31;H, 6.71;
3
1. Leung, D.;Abbenante, G.;Fairlie, D. P. J. Med. Chem. 2000,
43, 305±341.
1
0
15
N, 18.65. Found: C, 53.24;H, 6.76;N, 18.73.
2
. B oÈ hm, H. J.;Klebe, G.;Kubinyi, H. Wirkstoffdesign;Spek-
trum Akademischer Verlag GmbH: Heildelberg±Berlin±
Oxford, 1996;see p 469.
4
.1.18. ꢀ^)-N-[ꢀ2-{[Aminoꢀimino)methyl]amino}-4,5,6,7-
tetrahydro-1,3-benzothiazol-6-yl)methyl]-acetamide ꢀ19).
To a solution of bromoketone 7 /0.620 g, 2.5 mmol) in abs.
EtOH /15 mL) amidinothiourea /0.385 g, 3.25 mmol) was
added and the mixture was heated under re¯ux for 16 h.
The solvent was removed under reduced pressure to give a
slightly yellow foam. Water was added to the residue, the
solution was made alkaline with 1 M NaOH to pH 12 and
the mixture extracted with EtOAc /3£10 mL). The organic
extracts were washed with aq. NaCl /3£10 mL), dried
3. Sanderson, P. E. J.;Naylor-Olsen, A. M. Curr. Med. Chem.
1998, 5, 289±304.
4. Menear, K. Curr. Med. Chem. 1998, 5, 457±468.
5. Rewinkel, J. B. M.;Adang, A. E. P. Curr. Pharm. Des. 1999,
5, 1043±1075.
6. Wiley, M. R.;Fisher, M. J. Exp. Opin. Ther. Patents 1997, 7,
1265±1282.
7. Tucker, T. J.;Isaacs, R. C. A. The Development of Novel
Noncovalent Thrombin Inhibitors. Advances in Amino Acid
Mimetics and Peptidomimetics;Abell, A., Ed.;Jai Press:
New York, 1999;Vol. 2, p 53.
/Na SO ) and evaporated under reduced pressure to give 19
2 4
as a slightly brown solid;yield 0.260 g /39%);mp 247±
2
1
1
498C. IR /KBr): n 3375, 2919, 1652, 1610, 1540, 1452,
362, 1265, 1198, 981, 743, 642 cm . MS /EI): mꢀz /%)
83 /M , 22), 166 /100). H NMR /300 MHz, DMSO-d ):
21
8. Kimball, S. D. Curr. Pharm. Des. 1995, 1, 441±468.
9. /a) Peterlin-Ma sÏ i cÏ , L.;Kikelj, D. Tetrahedron 2001, 57,
7073±7105. /b) Peterlin-Ma sÏ i cÏ , L.;Kikelj, D. Tetrahedron
Lett. 2000, 41, 5589±5592.
10. Kikelj, D.;Peterlin-MasÏi cÏ , L.;Marinko, P.;Breznik, M.;Steg-
nar, M.;TrampusÏ-Bakija, A.;Fortuna, M. Patent application
WO 01ꢀ85760 /04.05.2001).
1
1
6
dˆ1.37±1.51 /m, 1H, 6-H), 1.82 /s, 3H, COCH ), 1.83±1.95
3
/
3
m, 2H, 5-H), 2.24±2.36, 2.50±2.80 /2£m, 4H, 4-H, 7-H),
.07 /t, 2H, Jˆ6.40 Hz, CH ), 7.96 /br t, 1H, NHCO), 8.11
2
/br s, 4H, NHC/NH)NH ). Anal. Calcd for C H N OS: C,
11 17
2
5
49.42;H, 6.41;N, 26.20. Found: C, 49.27;H, 6.23;N, 25.98.
1
1. Marinko, P.;Obreza, A.;Peterlin-Mas Ïi cÏ , L.;KrbavcÏi cÏ , A.;
Kikelj, D. J. Heterocycl. Chem. 2000, 37, 405±409.
2. St Laurent, D. R.;Balasubramanian, N.;Han, W. T.;Trehan,
A.;Federici, M. E.;Meanwell, N. A.;Wright, J. J.;Seiler,
S. M. Bioorg. Med. Chem. 1995, 3, 1145±1156.
4.1.19. ꢀ^)-6-ꢀAminomethyl)-4,5,6,7-tetrahydro-1,3-benzo-
thiazol-2-amine dihydrobromide ꢀ20). A solution of 18
1
/
/
100 mg, 0.44 mmol) in 47% aqueous hydrobromic acid
2 mL) was heated under re¯ux for 16 h. The excess HBr
was removed under reduced pressure and acetone was added
to the residue. The separated solid was collected by ®ltration
to yield a slightly brown crystalline solid;yield: 0.056 g
1
3. Bone, R.;Lu, T.;Illig, C. R.;Soll, R. M.;Spurlino, J. C.
J. Med. Chem. 1998, 41, 2068±2075.
1
4. Rewinkel, J. B. M.;Lucas, H.;van Galen, P. J. M.;Noach,
A. B. J.;van Dinther, T. G.;Rood, A. M. M.;Jenneboer,
A. J. S. M.;van Boeckel, C. A. A. Bioorg. Med. Chem. Lett.
1999, 9, 685±690.
/
70%);mp 326±328 8C. IR /KBr): n 3301, 2850, 1616,
2
568, 1489, 1443, 1016, 907, 779, 701 cm . MS /FAB):
1
1
mꢀz /%) 268 /MH , 100). H NMR /300 MHz, DMSO-d ):
1
1
6
dˆ1.43±1.57 /m, 1H, 6-H), 1.91±2.02 /m, 1H, 5-H), 2.05±
1
5. Feng, D. M.;Gardell, S. J.;Lewis, S. D.;Bock, M. G.;Chen,
Z.;Freidinger, R. M.;Naylor-Olsen, A. M.;Ramjit, H. G.;
Woltmann, R.;Baskin, E. P.;Lynch, J. J.;Lucas, R.;Schafer,
J. A.;Dancheck, K. B.;Chen, I. V.;Mao, S. S.;Krueger, J. A.;
Hare, T. R.;Mulichack, A. M.;Vacca, J. P. J. Med. Chem.
2
4
3
.17 /m, 1H, 5-H), 2.24±2.36, 2.40±2.57, 2.58±2.71 /3£m,
H, 4-H, 7-H), 2.86 /t, 2H, Jˆ6.41 Hz, CH N), 7.91 /br s,
2
1
H, NH ), 9.16 /br s, 3H, NH ). Anal. Calcd for
1
3
3
C H Br N S: C, 27.80;H, 4.35;N, 12.17. Found: C,
3
8
15
2
2
7.68;H, 4.33;N, 11.93.
1
997, 40, 3726±3733.
1
1
6. Becker, D. P.;Flynn, D. L. Synthesis 1992, 1080±1082.
7. Abdulla, R. F.;Fuhr, K. H. J. Org. Chem. 1987, 43, 4248±
Acknowledgements
4
250.
1
8. Bach, N. J.;Kornfeld, E. C.;Jones, N. D.;Chaney, M. O.;
Dorman, D. E.;Paschal, J. W.;Clemens, J. A.;Smalstig, E. B.
J. Med. Chem. 1980, 23, 481±491.
This work was supported ®nancially by the Ministry of
Science and Technology of the Republic of Slovenia. The
authors wish to thank Professor B. Stanovnik and the
Faculty of Chemistry and Chemical Technology, University
of Ljubljana for microanalyses.