Semisynthetic Di- and Tri-Functionalized Non-Immunosuppressive Cyclosporin A Derivatives as Potential Anti-HIV 1 Drugs

Article abstract of DOI:10.1055/s-2004-815405

A regio- and stereoselective synthesis of original semi-synthetic di- and tri-functionalized non-immunosuppressive cyclosporins by way of a Barton ester decarboxylation and a C-thioalkylation starting from cyclosporin A (CsA) and [4′-hydroxy-MeLeu]⁴-CsA is described.

Full text of DOI:10.1055/s-2004-815405

3
16
LETTER
Semisynthetic Di- and Tri-Functionalized Non-Immunosuppressive
Cyclosporin A Derivatives as Potential Anti-HIV 1 Drugs
N
J
on-Imm
u
e
nosuppres
a
sive Cyclos
n
porin A
D
er
-
Jean-Christophe Gueguen, Norbert Dereu, Bruno Filoche, Serge Sablé, Marc Vuilhorgne, Serge Mignani
Aventis Pharma S.A., Centre de Recherche de Paris, 13 quai Jules Guesde, B.P. 14, 94403, Vitry-sur-Seine Cedex France
Fax +33(1)58938014; E-mail: jean-christophe.carry@aventis.com
Received 21 October 2003
Dedicated to the memory of Dr. Jean-Claude Barrière and Dr. Marc Vuilhorgne.
nM) of 5c, we have now attempted to prepare new CsA
derivatives by the introduction of a third modification.
Thus, we decided to replace this allylic system by a corre-
Abstract: A regio- and stereoselective synthesis of original semi-
synthetic di- and tri-functionalized non-immunosuppressive
cyclosporins by way of a Barton ester decarboxylation and a C-thio-
alkylation starting from cyclosporin A (CsA) and [4¢-hydroxy- sponding bioisostere such as the methylthio group, as al-
4
5
MeLeu] -CsA is described.
ready prepared by Durette et al. The key chemical step
was the introduction of the methylthio group from the cor-
Key words: cyclosporin A derivatives, anti-HIV 1 drugs, Barton
ester radical decarboxylation, sulfide derivatives, thioxo-2H-pyri- responding carboxylic group using the Barton ester radi-
6
din-1-yl ester, C-thioalkylation
cal decarboxylation and trapping the generated carbon
radical with dimethyl disulfide.
The acquired immune deficiency syndrome (AIDS) is
caused by the human immuno-deficiency virus type 1
(
HIV 1), an RNA virus (Lentivirus) which infects and
destroys CD4 lymphocytes. T helper lymphocytes, mono-
cytes or/and microglial cells or/and endothelial cells can
be generally infected. Because of the limitations of cur-
rently available therapies, the search for new anti-HIV
agents remains an important field of medicinal chemistry
1
research.
It has been proposed that immunosuppression by cy-
closporin A (CsA) may have a beneficial effect on HIV
2
a
infection by blocking the T4 lymphocyte activation
which is required for HIV replication, and would act as an
indirect antiviral drug.2b
Figure 1
Few sulphide derivatives have been synthesized to date
using the Barton ester decarboxylation. For instance, pen-
The present report describes the regio- and stereoselective
synthesis and the pharmacological properties of the novel
CsA derivatives 5a and 5b (Scheme 1). These new semi-
7a
3
tadecylphenyl and n-pentadecylmethyl sulfides, and
7
b
1
7b-glucocorticoid butyrolactone sulfides were pre-
synthetic CsA derivatives that contain two or three func-
1
pared starting from their corresponding carboxylic acid
derivatives. To our knowledge, this is the first time that
such a strategy is used on the CsA scaffold.
tional modifications on the [MeBmt], the methylene
3
group of the [Sar] residue or/and the 4¢-hydroxylation of
4
the [MeLeu] residue, were tested for their in vitro anti-
HIV and immunosuppressive activities.
The targeted CsA derivatives 5a and 5b were synthesized
according to the sequences outlined in Scheme 1. Our
synthetic approach started from CsA and [(4¢-OH)Me-
In a previous paper, we described new non-immunosup-
pressive CsA analogues with anti HIV-1 activity. Thus,
4
4
Leu] -CsA. The latter was synthesized by an enzymatic
one of the most potent compounds (5c) possesses two
modifications: a dimethylaminoethylthio moiety with R-
4
hydroxylation of CsA at [MeLeu] by the strain Sebekia
3
benihana (35% yield without recycling, 50% with one re-
configuration on the [Sar] residue and a hydroxy group
4
cycling step, >90% HPLC purity) according to previously
on the [MeLeu] residue (Figure 1).
8
4
described work. CsA and [(4¢-OH)MeLeu] -CsA reacted
Encouraged by the strong anti-HIV-1 activity (IC of ca.
50
with acetic anhydride in the presence of triethylamine and
DMAP as bases to afford 1a and 1b in ca. 50% yield.
4
6 nM) and low immunosuppressive potency (IC50 1500
9
Then, oxidative cleavage of double bonds of 1a or 1b us-
ing a mixture of aqueous KMnO and NaIO afforded the
4
4
SYNLETT 2004, No. 2, pp 0316–0320
Advanced online publication: 12.01.2004
DOI: 10.1055/s-2004-815405; Art ID: G28103ST
0
2.
0
2.
2
0
0
4
10
corresponding CsA carboxylic acid derivatives 2a and
b in 80% and 57% yields, respectively. The next one-pot
2
©
Georg Thieme Verlag Stuttgart · New York

LETTER
Non-Immunosuppressive Cyclosporin A Derivatives
317
Scheme 1 Synthesis of di- and tri-functionnalized CsA derivatives 5a and 5b.
8
9
Reagents and conditions: a) See ref. , Sebekia benihana, 35% yield without recycling, 50% with one recycling step; b) 50%, see ref. (53%);
4
c) i) [(4¢-OH)MeLeu] -CsA (17.9 g, 15 mmol), Ac O (6 g, 58 mmol), DMAP (10.8 g, 88.5 mmol), Et N (12.4 mL, 87.5 mmol), CH Cl (205
2
3
2
2
mL), 36 h, r.t.; ii) H O (30 mL); iii) organic phase washed with H O (180 mL), dried with MgSO and the solution evaporated to dryness, then
2
2
4
the residue triturated in H O (150 mL) for 12 h, the solid filtered and washed with H O (100 mL); iv) chromatography on silica gel (EtOAc–
2
2
10
MeOH 19:1), 54%; d) 80%, see ref. ; e) see text, 57%; f) i) to 2a (12.5 g, 10 mmol) in 1,2-dichloroethane (100 mL), –15 °C was added distilled
N-methyl morpholine (1.2 mL, 10.7 mmol) then ClCO i-Bu (1.4 mL, 0.1 mmol) and the reaction mixture stirred for 1.5 h at –15 °C; ii) 2-mer-
2
captopyridine N-oxide sodium salt (1.5 g, 10 mmol), Et N (1.7 mL, 12 mmol), ClCH CH Cl (25 mL) and reaction mixture stirred in a flask
3
2
2
protected from light and covered with aluminum foil for 17 h at –20 °C; iii) distilled MeSSMe (8.9 mL, 99 mmol); iv) irradiation by two 60-
W tungsten filament lamps, 3 h, 0–10 °C; v) reaction mixture evaporated under reduced pressure and then triturated successively in Et O (200
2
mL), H O (100 mL) and 1 N HCl (20 mL); vi) organic phase washed with H O (3 × 50 mL) and 1 M HOCH CH NH (25 mL) then dried
2
2
2
2
2
(
MgSO ); vii) chromatography on silica gel (EtOAc, 32% g) see text, 27%; h) i) a solution of 0.5 M MeONa in MeOH and HN=C(NH ) ·HCl
4
2
2
(
0.31 g, 3.2 mmol) was added to 3a (3.75 g, 3 mmol) in MeOH (130 mL), r.t., 48 h: ii) Et O (100 mL) and organic phase washed with H O (3
2
2
×
50 mL) and dried (MgSO ); iii) chromatography on silica gel (EtOAc), 70%; i) i) to a solution of 3b (0.6 g, 0.46 mmol) in MeOH (25 mL)
4
was added 0.5 M MeONa (2 mL), r.t., 60 h; ii) reaction mixture evaporated under reduced pressure and triturated in H O (50 mL) and then
2
filtered, washed with H O (3 X 50 mL); iii) chromatography on silica gel (EtOAc–MeOH 9:1), 35%; j) i) a solution of 4a (0.1 g, 80 mmol) in
2
EtOH (3.5 mL) was filtered on 0.2 m Millipore; ii) Sebekia benihana, 72 h; iii) extraction of the reaction mixture with MeCN–n-heptane–MeOt-
Bu (2:1:1); iv) organic phase concentrated under reduced pressure and then triturated in MeOH (10 mL); v) chromatography on Sorbsil C60
silica gel (40–60 mm) [ClCH CH Cl then ClCH CH Cl–MeOH (49:1) flow: 20 mL/h], 39%; k) i) to a solution of LDA (3.3 mL, 23.3 mmol, 26
2
2
2
2
equiv), 1,3-dimethyl-(1H)-3,4,5,6-tetrahydropyrimidin-2-one (16.6 mL), distilled THF (33 mL), –70 °C was added 1.6 M n-BuLi (14.8 mL,
3.7 mmol) and the reaction mixture stirred for 20 min at 0 °C and cooled to –78 °C; ii) then 4a (1.1g, 0.9 mmol) in 1,3-dimethyl-(1H)-3,4,5,6-
tetrahydropyrimidin-2-one (14.5 mL) and distilled THF (27 mL) was added; iii) (Et NCH CH S) (5.2 g, 20 mmol), –78 °C for 2 h and then
2
2
2
2
2
0
°C for 20 h; iv) 1 N HCl (70 mL) and then Et O (100 mL); v) organic phase washed with H O (90 mL), dried (MgSO ), filtered and concen-
2
2
4
trated under reduced pressure; vi) residue (oil) triturated in pentane (150 mL); vii) chromatography on silica gel (EtOAc–MeOH 4:1); viii) chro-
matography on silica gel (EtOAc–n-BuOH–H O 6:3:3), 5a: 3% yield; l) see text, 5b: 35% yield, by the use of Na in liq. NH .
2
3
chemical transformation was 1) activation of 2a and 2b aluminum foil. The deacetylation reactions of 3a and 3b
with isobutyl chloroformate 2) addition of 2-mercaptopy- were carried out under standard reaction conditions
ridine N-oxide or 2-mercaptopyridine N-oxide sodium (MeONa, MeOH, r.t.) affording 4a and 4b in 69.5% and
salt in the presence of triethylamine giving the corre- 36% yields, respectively. Finally, C3-regio and stereose-
sponding thiohydroxamic esters 3) addition of dimethyl lective thioalkylation of 4a or 4b was performed by the
disulfide 4) irradiation of the reaction mixture. Com- condensation of di-(3-dimethylaminoethyl) disulfide and
pounds 3a and 3b were obtained in 32% and 27% overall di-(3-diethylaminoethyl) disulfide with the respective
yields, respectively. Note, that steps a) b) and c) were per- polylithio derivatives of 4a or 4b. These polyanion inter-
formed in a flask protected from light and covered with mediates were prepared in situ by the action of a strong
Synlett 2004, No. 2, 316–320 © Thieme Stuttgart · New York

3
18
J.-C. Carry et al.
LETTER
base, either lithium diisopropylamide (LDA, ca. 26 equiv) ation and the trapping of the generated carbon radical with
followed by the addition of n-BuLi (ca. 26 equiv) in a dimethyl disulfide affording modifications on the [MeB-
1
1
,3-dimethyl-(1H)-3,4,5,6-tetrahydropyrimidin-2-one/
mt] 2) regioselective and stereoselective C-thioalkylation
3
4
THF mixture at –78 °C, according to a procedure de- of [Sar] of both CsA and [4¢-hydroxy-MeLeu] -CsA us-
scribed previously by Seebach,11 giving 5a in non-op- ing sodium amide in liquid ammonia or LDA/n-BuLi as a
12
1
4
timized 3% yield or Na (ca. 13 equiv) in liq. NH at strong base. The liquid ammonia experimental conditions
33 °C affording 5b in 35% yield. Interestingly, the en- made the preparation of 5b valuable for preparative scale,
3
1
3
–
4
zymatic hydroxylation at [MeLeu] of 4a using Sebekia and could be used for the functionalization of peptides and
benihana gave 4b in 39% yield (without recycling) close other cyclopeptides.17 This therefore represents an origi-
to the yield obtained for the preparation of [(4¢-OH)Me- nal and useful method for the functionalization of CsA
Leu] -CsA from CsA. As observed previously by Seebach and [(4¢-OH)MeLeu] -CsA at position 3 without excess of
and Papageorgiou using LDA/n-BuLi (eventually in n-BuLi.11
4
4
1
1
presence of dry LiCl) and then by us using both LDA/n-
BuLi or sodium amide/liquid ammonia as base, only
the substitution of the a protons of the [Sar] residue was
4
,14
Acknowledgment
3
observed, resulting in the formation of a CsA derivative We thank F. Begassat, H. Bomo, S. Conge, J.-F. Ferron, C. Gaudin,
3
F. Gasse, R. Guesdon, M. Jacob-Rouquet, J. Lebert, S. Lebitoux, O.
Leyris, C. Molherat, C. Nachmansohn, M. Roy-Saint Martin for
technical assistance, and A. Bousseau and Y. Henin for the biologi-
cal experiments.
having a R configuration at [Sar]. The relative stereo-
chemistry of the former sarcosine residue was determined
by H NMR spectroscopy by comparison with already
described analogues.
1
1
5
In order to extend the exploration of the Barton ester rad-
ical decarboxylation of CsA-derivative 2b with the goal to
prepare new CsA-derivatives, we transformed the carbox-
ylic function of 2b into the corresponding methyl moiety
References
(1) (a) Corbett, J. W. Current Medicinal Chemistry: Anti-
Infective Agents 2002, 1, 119. (b) Gupta, S. P. Progress in
Drug Research 2002, 58, 223. (c) Balzarini, J.; De Clercq,
E. Antiretroviral Therapy 2001, 31. (d) Balzarini, J.;
Esnouf, R.; De Clercq, E. Antiretroviral Therapy 2001, 63.
(
compound 2c, Scheme 2). This radical reaction occurred
via the photochemically-induced decarboxylative rear-
rangement of the corresponding thioxo-2H-pyridin-1-yl
ester in the presence of distilled cyclohexanethiol as initi-
(
2) (a) Andrieu, J. M.; Even, P.; Venet, A. AIDS Res. Hum.
Retroviruses 1986, 2, 163; and references cited therein.
(b) See, for example: Zagury, D.; Bernard, J.; Leonard, R.;
Cheynier, M.; Feldman, M.; Sarin, P. S.; Gallo, R. C.
Science 1986, 231, 850; and references cited therein.
3) Evers, M.; Mignani, S.; Carry, J.-C.; Filoche, B.; Bashiardes,
G.; Bensoussan, C.; Guegen, J.-C.; Barrière, J.-C. Pat. Appl.
WO 98-19980427, 1998; Chem. Abstr. 1998, 130,4088.
6
ator/radical scavenger to give 2c in 62% yield. Finally,
di-deacetylation of 2c under standard experimental reac-
tion conditions (MeONa/MeOH) afforded 2d in 43%
yield.
(
In conclusion, we have developed a rapid and useful syn-
thetic route towards CsA derivative 5a and [4¢-hydroxy-
(4) Evers, M.; Barrière, J.-C.; Bashiardes, G.; Bousseau, A.;
Carry, J.-C.; Dereu, N.; Filoche, B.; Henin, Y.; Sablé, S.;
Vuilhorgne, M.; Mignani, S. Bioorg. Med. Chem. Lett. 2003,
4
MeLeu] -CsA derivative 5b (which show in vitro anti-
1
6
HIV activity) via 1) the Barton ester radical decarboxyl-
13, 4415; and references cited therein.
Scheme 2 Reagents and conditions: a) i) To 2b (4.2 g, 3.2 mmol) in 1,2-dichloroethane (43 mL) at –15 °C was added distilled N-methyl mor-
pholine (0.4 mL, 3.6 mmol) then ClCO i-Bu (0.4 mL, 3.2 mmol) and the reaction mixture was stirred for ca. 2 h at –15 °C; ii) 2-mercaptopy-
2
ridine N-oxide sodium salt (1.3 g, 9 mmol), Et N (3 mL, 21 mmol), ClCH CH Cl (10 mL) were added and the reaction mixture was stirred in
3
2
2
a flask protected from light and covered with aluminum foil for 44 h at –15 °C; iii) distilled cyclohexyl mercaptan (4.5 mL, 37 mmol); iv) ir-
radiation by two 100 W tungsten filament lamps, 4 h, 0–5 °C; v) organic phase washed with H O (150 mL) and dried (MgSO ); vi) chromato-
2
4
graphy on silica gel (EtOAc), 62%; b) 2c (2.5 g, 2 mmol), 0.5 M MeONa in MeOH (11.3 mL), MeOH (95 mL), r.t., 140 h, 43%.
Synlett 2004, No. 2, 316–320 © Thieme Stuttgart · New York

LETTER
Non-Immunosuppressive Cyclosporin A Derivatives
319
(
5) See, for example: (a) Witzel, B. W. Pat. Appl. GB
205317A, 1988; Chem. Abstr. 1988, 111; 97726.
b) Durette, P. L.; Pessolano, A. A.; Kollonitsch, J.; Witzel,
B. W. Pat. Appl. GB 2227244A, 1990; Chem. Abstr. 1990,
14, 7266.
H O (200 mL), and the suspension treated with
ethanolamine (1.1 mL). The mixture was filtered, and the
2
2
(
resulting solution was washed with Et O (4 × 100 mL). The
2
aqueous layer was acidified to pH 1 with 5 N HCl, extracted
with EtOAc (2 × 300 mL) and the combined organic extracts
were washed with H O (2X100 mL), dried (MgSO ) and
1
(
6) See, for example: (a) Barton, D. H. R.; Hervé, Y.; Potier, P.;
2
4
Thierry, J. J. Chem. Soc., Chem. Commun. 1984, 1298.
concentrated in vacuo to afford 2b (6.8 g, 57%) as a white
(
b) Barton, D. H. R.; Bridon, D.; Hervé, Y.; Potier, P.;
Thierry, J.; Zard, S. Z. Tetrahedron 1986, 42, 4983.
c) Barton, D. H. R.; Hervé, Y.; Potier, P. Tetrahedron 1989,
5, 6309. (d) Barton, D. H. R.; Géro, S. D.; Quiclet-Sire, B.;
powder, TLC R = 0.42 (5% MeOH in CH Cl ). LSI-MS:
m/z = 1306 (M + H) .
f
2
2
+
(
4
Compound 3b: To a solution of 2b (6 g, 4.6 mmol) in 1,2-
dichloroethane (60 mL) under nitrogen at –15 °C in a flask
protected from light (aluminum foil), were successively
added distilled N-methylmorpholine (0.56 mL, 5 mmol) and
distilled isobutyl chloroformate (0.66 mL, 48.5 mmol). The
reaction mixture was stirred for 2.5 h at the same
Samadi, M. Tetrahedron 1992, 48, 1627; and references
cited therein.
(
7) (a) Barton, D. H. R.; Bridon, D.; Zard, S. Z. Heterocycles
1
987, 25, 449. (b) Procopiou, P. A.; Biggadike, K.; English,
A. F.; Farrell, R. M.; Hagger, G. N.; Hanock, A. P.; Haase,
M. V.; Irving, W. R.; Sareen, M.; Snowden, M. A.; Solanke,
Y. E.; Tralau-Stewart, C. J.; Walton, S. E.; Wood, J. A. J.
Med. Chem. 2001, 44, 602.
temperature. Then, a solution of 2-mercaptopyridine N-
oxide (0.7 g, 5.5 mmol) and Et N (0.78 mL, 5.5 mmol) in
3
1,2-dichloroethane (15 mL) was added dropwise in 15 min,
and the reaction mixture was stirred for 17 h at –20 °C.
Finally, distilled dimethyl disulfide (4.1 mL, 45.5 mmol)
was added dropwise, and the reaction mixture was subjected
to irradiation by two 60-W tungsten filament lamps that were
placed close to the reaction vessel at 0–10 °C for 3 h, and
then allowed to warm to r.t. The reaction mixture was
concentrated under reduced pressure, and the residue was
(
(
8) Young, K. S.; Kobel, H.; Rosenwirth, B.; Seebach, D.;
Traber, R.; Wenger, R.; Bollinger, P. Eur. Pat. Appl. EP
0484281A2, 1991; Chem. Abstr. 1991, 117, 129961.
9) Traber, R.; Loosli, H.; Hoffman, H.; Kuhn, M.; Von
Wartburg, A. Helv. Chim. Acta 1982, 65, 1655.
10) Paprica, P. A.; Margaritis, A.; Petersen, N. O. Bioconjugate
Chem. 1992, 3, 32.
(
(
triturated in Et O (200 mL) and 1 N HCl (20 mL). The
2
11) (a) Seebach, D. Eur. Pat. Appl. EP 194972, 1987; Chem.
Abstr. 1987, 107, 7610. (b) Seebach, D.; Beck, A. K.;
Bossler, H. G.; Gerber, C.; Ko, S. Y.; Murtiashaw, C. W.;
Naef, R.; Shoda, S.-I.; Thaler, A.; Krieger, M.; Wenger, R.
Helv. Chim. Acta 1993, 76, 1564. (c) Mikol, V.;
organic layer was successively washed with H O (3 × 50
2
mL), 1 M aq ethanolamine (50 mL) and H O (3 × 50 mL),
2
dried (MgSO ) and concentrated in vacuo to give a solid
4
which was purified by chromatography on silica gel eluting
with EtOAc–MeOH (19:1) to give 3b (1.6 g, 27%) as a white
Papageorgiou, C.; Borer, X. J. Med. Chem. 1995, 38, 3361.
powder, TLC R = 0.58 (10% MeOH in EtOAc), LSI-MS:
m/z = 1308 (M + H) . Compound 5b: Sodium (0.05 g, 2.2
f
+
(
d) Papageorgiou, C.; Sanglier, J.-J.; Traber, R. Bioorg. Med.
Chem. Lett. 1996, 6, 23.
mmol) and Fe(NO ) ·9 H O (0.01 g, 0.027 mmol) were
3
3
2
(
12) Compound 5a: white solid, mp 140 °C; TLC R = 0.72 (10%
added to a stirred solution of anhyd liquid NH (70 mL) at
f
3
1
MeOH in CH Cl ). H NMR (CDCl ): two conformers (75–
–33 °C. When the reaction mixture changed from a blue
solution to a grey suspension, additional sodium (0.6 g, 26
mmol) was introduced portionwise in 15 min, and the
reaction mixture was stirred at –33 °C for 1.5 h. Then, 4b
(2.4 g, 2 mmol) in tert-butylmethylether (80 mL) was added
dropwise in 30 min at –33 °C, followed by the addition of di-
(3-dimethylaminoethyl) disulfide (1.6 g, 7.8 mmol) in tert-
butylmethylether (10 mL). The reaction mixture was stirred
2
2
3
2
5 ratio), partial description, d = 1.37 (d, J = 7.5 Hz, 3 H,
CH 7b), 2.00 and 2.03 (s, 3 H, SCH 1d), 2.30–2.90 [m, 11
H, SCH CH N(CH ) 3a, SCH 1d and CH 5b], 3.80 (m, 1
3
3
2
2
3
2
2
H, CH 1b), 3.90 (broad d, J = 6.0 Hz, 1 H, OH in 1b), 4.54
and 4.60–4.70 (two m, 1 H, CH 7a), 4.60–4.70 (m, 1 H, CH
5a), 4.80 (m, 1 H, CH 8a), 4.80–5.40 (m, 4 H, CH 2a and CH
a of three leucine residues), 5.49 and 5.66 (two d, J = 6.0 Hz
and J = 9.0 Hz, respectively, 1 H, CH 1a), 5.72 (dd, J = 10.5
and 4.0 Hz, 1 H, CH a, leucine residue), 5.79 and 5.98 (2 s,
at the same temperature for 30 min, and NH Cl (2.3 g) was
4
added portionwise. The reaction mixture was stirred
overnight and allowed to warm up to r.t. Then, the reaction
1
H, CH 3a), 7.05 and 7.17 (two d, J = 8.0 Hz, 1 H, CONH
in 8), 7.32 and 7.35 (two d, J = 9.0 Hz, 1 H, CONH in 5),
.42 and 7.76 (two d, J = 7.5 Hz, 1 H, CONH in 7), 7.94
broad d, J = 10.0 Hz, 1 H, CONH in 2). IR (CH Cl ): g
mixture was diluted with Et O (100 mL) and filtered. The
2
7
solid was washed with Et O (3 × 100 mL), and the combined
2
(
3
=
max
organic extracts were concentrated under reduced pressure
to give an oil which was triturated in pentane (200 mL) for
48 h. The resulting solid was filtered and washed with
pentane (3 × 50 mL). Finally, the solid was purified by
chromatography on silica gel eluting with EtOAc–MeOH
(9:1) to give 5b (0.9 g, 35%) as a white solid, mp 154 °C;
2
2
–
1
415, 3325, 2990, 2875, 1637, 1510, 1470, 1035 cm . LSI-
+
MS: m/z = 1340 (M + H) .
(
13) Typical Experimental Procedures are as follows:
Compound 2b: To a solution of 1b (12 g, 9 mmol) in tert-
butanol (750 mL) were added successively a solution of
Na CO (7.6 g, 72 mmol) in H O (200 mL), NaIO (15.7 g,
1
TLC R = 0.38 (10% MeOH in CH Cl ). H NMR (CDCl ):
2
3
2
4
f
2
2
3
7
3.5 mmol) in H O (200 mL) and dropwise a solution of
d = 1.36 (d, J = 7.5 Hz, 3 H, CH 7b), 2.04 (s, 3 H, SCH 1e),
2
3
3
KMnO (0.29 g, 1.8 mmol) in H O (200 mL) at 30 °C. The
reaction mixture was stirred for 36 h at r.t. then a solution of
KMnO (0.1 g, 0.62 mmol) in H O (70 mL) was added
2.25 [s, 6 H, N(CH ) 3a], 2.20–2.80 (m, 7 H, CH 1g -
3 2 2
4
2
NCH CH S 3a and 1 H of CH 4b), 2.70–2.72, 3.13–3.18,
2 2 2
3.28–3.45 and 3.51 (seven s, 3 H each, 7 NCH ), 3.64 (d,
4
2
3
dropwise at r.t. The solution was stirred for an additional 3 h
at r.t. Then, a solution of NaHSO (47 g, 0.45 mmol) in H O
J = 6.5 Hz, 1 H, OH 1b), 3.90 (m, 1 H, CH 1b), 4.50 (m, 1
H, CH 7a), 4.67 (t, J = 9.0 Hz, 1 H, CH 5a), 4.80 (m, 1 H,
CH 8a), 4.90–5.10 (m, 3 H, CH 2a and CH a of two leucine
residues), 5.15 (d, J = 11.0 Hz, 1 H, CH 11a), 5.42 (d,
J = 6.5 Hz, 1 H, CH 1a), 5.46 (t, J = 6.0 Hz, 1 H, CH 4a),
5.71 (dd, J = 11.0 and 4.0 Hz, 1 H, CH a of one leucine),
6.00 (s, 1 H, CH 3a), 7.22 (d, J = 8.0 Hz, 1 H, CONH in 8),
7.50 (d, J = 9.0 Hz, 1 H, CONH in 5), 7.72 (d, J = 7.5 Hz, 1
3
2
(
200 mL) was added dropwise in 30 min, followed by 2 N
H SO (200 mL). The reaction mixture was washed with
2
4
Et O (3 × 300 mL), and the combined organic extracts were
2
dried (MgSO ) and concentrated under reduced pressure to
4
give a solid which was triturated in H O (300 mL), filtered
2
and washed with H O (200 mL). The residue was mixed with
2
Synlett 2004, No. 2, 316–320 © Thieme Stuttgart · New York

3
20
J.-C. Carry et al.
LETTER
H, CONH in 7), 8.03 (d, J = 10.0 Hz, 1 H, CONH in 2). IR
(16) The in vitro anti-HIV activity of compounds 5a and 5b was
4
(
1
CH Cl ): g = 3409, 3319, 2965, 2873, 1637, 1514, 1469,
measured in established cell line cultures (see ref. ). Thus,
2
2
max
–
1
+
411, 1095 cm . LSI-MS: m/z = 1327 (M + H) . Anal.
the CEM4 cell line was infected with HIV-1Lai strain. The
inhibition of HIV replication in the culture was estimated by
the measure of the reverse transcriptase (RT) produced in the
supernatant. Anti-viral activity was expressed as the IC50
RT, the concentration required to reduce replication of HIV
by 50%, and was determined by linear regression.
Calcd for C H N 0 S : C, 57.89; H, 8.96; N, 12.66; O,
6
4
118 12 13 2
15.66; S, 4.83. Found: C, 57.06; H, 8.47; N, 12.59; S, 3.48;
water, 1.1%.
(
14) For other examples using sodium amide as a base in liquid
ammonia, see: (a) Barrière, J.-C.; Bashiardes, G.; Carry,
J.-C.; Evers, M.; Filoche, B.; Leconte, J.-P.; Mignani, S. Pat.
Appl. WO 9828329A1, 1996; Chem. Abstr. 1996, 129,
Compounds 5a and 5b displayed IC ’s lower than 100 nM.
5
0
(17) To our knowledge, no peptide or cyclopeptide has been
treated with sodium amide/liquid ammonia as a base to give
the corresponding polyanion before.
1
49255. (b) Barrière, J.-C.; Bashiardes, G.; Carry, J.-C.;
Evers, M.; Filoche, B.; Mignani, S. Pat. Appl. WO
828330A1, 1996; Chem. Abstr. 1996, 129, 149254.
c) Barrière, J.-C.; Bashiardes, G.; Carry, J.-C.; Evers, M.;
Filoche, B.; Leconte, J.-P.; Mignani, S. Pat. Appl. WO
828328A1, 1996; Chem. Abstr. 1996, 129, 149253.
d) Amouret, G.; Guerreiro, A.; Viskov, C.; Mignani, S.;
9
(
For C-alkylation of residues of linear/cyclic peptides, see:
(a) Seebach, D.; Bossler, H.; Gründler, H.; Shoda, S.-I.;
Wenger, R. Helv. Chim. Acta 1991, 74, 197. (b) Miller, S.
A.; Griffiths, S. L.; Seebach, D. Helv. Chim. Acta 1993, 76,
563. (c) Bossler, H. G.; Seebach, D. Helv. Chim. Acta 1994,
77, 1124. (d) Seebach, D.; Bezençon, O.; Jaun, B.;
Pietzonka, T.; Matthews, J. L.; Kühnle, F. N.; Schweizer, W.
B. Helv. Chim. Acta 1996, 79, 588.
9
(
Evers, M.; Barrière, J.-C.; Bashiardes, G.; Carry, J.-C.;
Filoche, B. Pat. Appl. WO 9932512A1, 1999; Chem. Abstr.
1999, 131, 59141.
(
15) Aebi, J. D.; Guillaume, D.; Dunlap, B. E.; Rich, D. H. J.
Med. Chem. 1988, 31, 1805.
Synlett 2004, No. 2, 316–320 © Thieme Stuttgart · New York