Hydroxylated analogues of the orally active broad spectrum antifungal, Sch 51048 (1), and the discovery of posaconazole [Sch 56592; 2 or (S,S)-5]

Article abstract of DOI:10.1016/j.bmcl.2005.09.031

As part of a detailed study, the syntheses, biological activities, and pharmacokinetic properties of hydroxylated analogues of the previously described broad spectrum antifungal agents, Sch 51048 (1), Sch 50001 (3), and Sch 50002 (4), are described. Based on an overall superior profile, one of the alcohols, Sch 56592 (2), was selected for clinical studies.

Full text of DOI:10.1016/j.bmcl.2005.09.031

Bioorganic & Medicinal Chemistry Letters 16 (2006) 186–190
Hydroxylated analogues of the orally active broad
spectrum antifungal, Sch 51048 (1), and the discovery of
posaconazole [Sch 56592; 2 or (S,S)-5]
Frank Bennett,* Anil K. Saksena, Raymond G. Lovey, Yi-Tsung Liu, Naginbhai M. Patel,
Patrick Pinto, Russel Pike, Edwin Jao, Viyyoor M. Girijavallabhan, Ashit K. Ganguly,
David Loebenberg, Haiyan Wang, Anthony Cacciapuoti, Eugene Moss,
Fred Menzel, Roberta S. Hare and Amin Nomeir
Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
Received 23 June 2005; accepted 8 September 2005
Abstract—As part of a detailed study, the syntheses, biological activities, and pharmacokinetic properties of hydroxylated analogues
of the previously described broad spectrum antifungal agents, Sch 51048 (1), Sch 50001 (3), and Sch 50002 (4), are described. Based
on an overall superior profile, one of the alcohols, Sch 56592 (2), was selected for clinical studies.
ꢀ 2005 Elsevier Ltd. All rights reserved.
The incidence of life-threatening Candidiasis, Crypto-
coccus, and Aspergillosis have increased significantly
over the last several decades due to the development
of new intensive chemotherapy regimens, use of high-
dose corticosteroids, and increased use of immunosup-
pressive regimens for autoimmune diseases.1
O
H
N
R'
O
N
N
N
F
N
O
N N
F
1: Sch 51048
R'=
N
R'=
R'=
3: Sch 50001
R
4: Sch 50002
S
Currently, antifungal therapies can be limited because of
toxicity, low efficacy rates, and drug resistance. Despite
the introduction of new formulations of older drugs
(i.e., cyclodextrin—itraconazole2 and PEG—amphoteri-
cin B3), the search for relatively less toxic and more effi-
Figure 1. Structures of Sch 51048 (1), Sch 50001 (3), and Sch 50002 (4).
eight possible secondary alcohols represented by sub-
structures 5–7 (Fig. 2).
cacious treatments continues. As
a
result the
development of new azoles, such as voriconazole4 and
ravuconazole,5 has come to the forefront. Concurrently,
as part of an extensive, detailed campaign we previously
reported the in vitro antifungal activities and efficacy
studies in animal models of some of or lead compounds
1, 3, and 4 (Fig. 1).6
In addition to providing polar functionality to these
hydrophobic molecules, the alcohols can be used as a
OH
R'=
As a continuation of these studies we would now like to
report on the syntheses and biological activities of all
5
S
R
7
6
HO
HO
Keywords: Antifungal; Posaconazole.
*
Figure 2. Structures of secondary alcohols Sch 51048 (5), Sch 50001
(6), and Sch 50002 (7).
Corresponding author. Tel.: +1 908 7403 103; fax: +1 908 7407
152; e-mail: frank.bennett@spcorp.com
0960-894X/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.09.031

F. Bennett et al. / Bioorg. Med. Chem. Lett. 16 (2006) 186–190
187
oxymethyl ether 12.7 DIBAL-H reduction provides the
propanal 13 which, on exposure to ethyl magnesium
bromide, generates the Ôchelation controlledÕ–(S,S)–al-
cohol 14 identified by removal of benzyloxymethyl ether
and compared with the known diols,8 along with its rel-
atively polar (S,R)-isomer 15 (14:15; at 6:1 in diethyl
ether as the solvent, at 2:1 in THF), which were partially
separated by careful column chromatography on silica
gel. The alcohol 14 is transformed into the brosylate
16, which is displaced in a SN2 manner with the anion
generated from the triazolone 8 and cesium carbonate
in hot DMF. Finally, the benzyloxymethyl ether is
removed by hydrolysis in acidic media to the desired
target (S,R)-5 (Sch 56588).9
Ar (Triazolone)
O
H
R
NH
+
O
N
N
N
F
N
X
O
N N
PO
F
9
8
N
X= leaving group
P= protecting group
R= alkyl groups
O
R
H
O
N
O
N
N
N
F
N
PO
N N
F
Hydroxylated
Analogs, P= H
10
N
Figure 3. General synthetic approach to hydroxylated analogues (5–7).
Using the same sequence of events, the (S,R) isomer
alcohol 15 was transformed into (S,S)-5 or posaconaz-
ole 2 (Sch 56592),10 via the brosylate 17. Similarly, using
the chemistry described in Scheme 1 and (D)-lactate as
starting material, (R,R)-5 and (R,S)-5 can be
synthesized.
handle to prepare water-soluble prodrugs for iv admin-
istration where the oral route is impractical (e.g., AIDS
and cancer patients). Our general synthetic approach is
shown in Figure 3 involving the anion generated from
the known triazolone 8,6 requiring chiral syntheses of
the electrophilic side chains 9. Following alkylation,
removal of the protecting group provides the desired
alcohols 10.
Preparation of the representatives of substructure 7 is
shown in Schemes 2 and 3. The commercially available
(R,R)-2,3-butane diol 18 was converted to the benzyli-
dene acetal 19, which was subsequently reduced to the
benzyl ether 20 and then the brosylate 21. Alkylation
and removal of the benzyl protective group provides
(R)-7 as Sch 56984.11
Beginning with methyl (S)-lactate, the syntheses of two
of the possible four diastereomers represented by sub-
structure 5 are shown in Scheme 1. The methyl ester
11 is converted directly into the corresponding benzyl-
The corresponding (S)-isomer was also obtained from
intermediate 20. MartinÕs version of the Mitsonobu
reaction12 provided the benzoate 22. Saponification
and protection of the resulting alcohol 23 provided the
acetal 24. The benzyl ether was removed via catalytic
hydrogenation and activation of the carbinol 25 to the
corresponding p-bromotoluenesulfonate 26 prior to
alkylation with the anion of the triazolone 8. Finally,
hydrolysis of the silyl alcohol 27 under acidic condition
gave the (S)-7 alcohol.
H
OMe
OH
OMe
OCH2OBn
12
b
a
O
O
O
OCH2OBn
13
S
Me
Me
Me
11
c
Me
Me
Using the same sequence of events compounds repre-
sented by substructure 6 can be prepared from (S,S)-
2,3-butane diol.
R
S
HO
HO
+
S
Me
OCH2OBn
14
OCH2OBn
15
S
Me
All compounds proved to be very active in vitro against
Candida albicans and Aspergillus species (Table 1).
d
d
Me
Me
Me
Me
R
BsO
O
C6H5
BsO
Me
HO
Me
a
b
HO
OCH2OBn
Me
Me
OCH2OBn
OBn
O
R
OH
18
Me
Me
16
17
20
19
e,f
O
e,f
c
O
Me
OH
Me
OBn
21
O
d, e
Me
OH
Me
S
S
BsO
Me
N
N
Ar
R
S
N
N
N
Ar
N
N
Ar
R
N
OH
N
Me
Me
Me
(S,R)-5
(R)-7 (Sch 56984)
2 (Posaconazole)
Scheme 1. Reagents and conditions: (a) benzyl chloromethyl ether; (b)
DIBAL-H; (c) EtMgBr, diethyl ether or THF, ꢀ78 ꢁC to rt; (d) brosyl
chloride, DMAP; (e) 8, Cs2CO3, DMF, heat; (f) 6 N HCl (aq), MeOH.
Scheme 2. Reagents and conditions: (a) benzaldehyde, TsOH, heat;
(b) DIBAL-H; (c) p-bromosulfonyl chloride, DMAP; (d) 8, Cs2CO3,
DMF, heat; (e) catalytic hydrogenation.

188
F. Bennett et al. / Bioorg. Med. Chem. Lett. 16 (2006) 186–190
HPLC
Me
OBn
20
Me
OBn
22
Me
OBn
23
400
350
300
250
200
150
a
b
HO
Me
PNBO
Me
HO
Me
56592 (MC)
•
•
PNB = p-Nitrobenzoyl
c
•
56984 (MC)
56588 (MC)
•
Me
OBn
24
Me
OBs
Me
d
e
•
•
SEMO
Me
SEMO
Me
SEMO
Me
100
50
0
•
OH
25
•
•
•
•
•
•
•
51048 (HPßCD)
26
•
0
20
40
60
80
100
120
140
160
f
Dose (mg/kg)
Chart 1. Mouse dose response (PO).
O
O
Me
OH
g
Me
N
N
Ar
N
N
Ar
S
N
OSEM
S
N
HPLC
56592 (t 1/2 22 hrs.)
0.4
0.3
0.2
Me
,
Me
•
•
(S)-7
27
Scheme 3. Reagents and conditions: (a) 4-nitrobenzoic acid, PPh3,
DEAD; (b) 1 N NaOH (aq); (c) SEM-Cl, i-Pr2NEt; (d) H2–10% Pd/C;
(e) BsCl, Py; (f) 8, Cs2CO3, DMF, 80 ꢁC; (g) HCl (aq).
•
•
51048
56588
•
0.1
0
Table 1. Antifungal activities of alcohols 5, 6, and 7
•
•
•
•
•
Compound
Candida albicans Aspergillus sp.
(geomean MIC, (geomean MIC,
• •
56984
•
•
•
•
• •
•
lg/ml)a
lg/ml)a
12
18
24
30
36
42
48
0
6
Time (hours)
(R,R)-5
(R,S)-5
0.014
0.019
0.022
0.018
<0.077
<0.086
<0.090
<0.048
Chart 2. PO, 10 mpk, C. monkeys.
(S,R)-5 (Sch 56588)
(S,S)-5 (or 2; posaconazole,
Sch 56592)
56592 prolonged the survival of mice longer than Sch
51048.16,17 Sch 56588, Sch 56984, and fluconazole
(FLZ) at the same dose.
(R)-6
(S)-6
<0.006
0.030
0.090
0.080
(R)-7 (Sch 56984)
(S)-7
<0.007
0.020
<0.050
0.060
Sch 56592 was similar to Sch 56588 and Sch51048 in
prolonging the survival of immunocompromised mice
infected (pulmonary) with Aspergillus fumigatus
ND159. Sch 56984 was less effective and itraconazole
(ITZ; 100 mg/kg) was ineffective (Chart 4).16,17
a Geometric mean MIC values were determined against 26–30 strains
of C. albicans, and 37 strains of Aspergillus species, including 17
A. fumigatus, 11 A. flavus, 5 A. niger, and 4 A. terreus as described
previously.13 The geomean MICs for Sch 51048 were 0.020–0.053 for
C. albicans; 0.20–0.32 for Aspergillus sp.
A selection of these potent antifungal agents Sch 56588
and Sch 56592, both containing 5-carbon side chains,
prepared from readily available L-lactate and one ana-
logue containing a 4-carbon side chain, Sch 56984, were
then examined in vivo. In mice (Chart 1), Sch 56592 and
Sch 56984 had similar serum levels following oral
administration to mice. These compounds exhibited
considerably higher blood levels relative to Sch 56588
and Sch 51048 when administered from 20 to 150 mpk.14
RX: PO- 1xDx4D- 2.5 MG/KG
100
• • • • • • • • • •
56592
• • • • • • •
•
•
80
60
40
20
0
• • • •
•
•
• •
• •
51048
• • • •
VEHICLE
• •
FLZ
In cynomolgus monkeys at 10 mpk (Chart 2) Sch 56592
clearly demonstrated higher serum levels relative to Sch
56588, Sch 56984 or Sch 51048.15,16
56984 • • • •
56588
• •
• • • •
•
Subsequently, the compounds were examined in infec-
tion models. Sch 56592 (2.5 mg/kg) was the most effec-
tive antifungal against C. albicans C72 systemic
infection in immunocompromised mice (Chart 3). Sch
0
1
2
3
4
5
6
7
8
9
10
11
12
DAYS
Chart 3. Candida albicans, C72 systemic infection in mice.

F. Bennett et al. / Bioorg. Med. Chem. Lett. 16 (2006) 186–190
189
7. Still, W. C.; Schneider, J. A. Tetrahedron Lett. 1980, 21,
1035.
8. Enders, D.; Nakai, S. Chem. Ber. 1991, 124, 219.
RX: PO-1xDx4D- 10MG/KG
100
80
60
40
20
0
• • • •
25
9. Selected analytical data: Sch 56588: ½aꢁD ꢀ20.1 (c 1.02,
25
CHCl3); ½aꢁD ꢀ20.8 (c 0.35, CHCl3). 1H NMR (CDCl3,
•
400 Hz) d 8.11 (s, 1H), d 7.80 (s, 1H), d 7.64 (s, 1H), d 7.42
(m, 2H), d 7.39 (m, 1H), d 7.03 (m, 2H), d 6.94 (m, 2H), d
6.86 (m, 1H), d 6.83 (m, 1H), d 6.78 (m, 2H), d 4.65–4.51
(d, J = 14.4 Hz, d, J = 14.4 Hz, 2H), d 4.17 (m, 1H), d
4.12–3.78 (dd, J = 8.7, 7.4 Hz, dd, J = 8.7, 3.8 Hz, 2H), d
4.07 (dt, J = 10.9, 3.4, 3.4 Hz, 1H), d 3.71–3.62 (dd,
J = 8.9, 5.5 Hz, dd, J = 8.9, 7.1 Hz, 2H), d 3.38 (m, 4H), d
3.30 (d, J = 2.6 Hz, 1H), d 3.23 (m, 4H), d 2.61 (m, 1H), d
2.56–2.08 (m, J = 12.3, 8.0, 2.5 Hz, dd, J = 12.3, 8.0 Hz,
2H), d 2.02–1.87 (mm, 2H), d 1.25 (d, J = 6.5 Hz, 3H), d
0.91 (t, J = 7.4 Hz, 3H). HR-FABMS calcd for
C37H43N8O4F2: 701.3375. Found: 701.3385 (M+H)+.
•
• •
56592
• • • • • • •
56588
• • •
56984
51048
• •
ITZ
•
(100MPK)
• • •
•
4
VEHICLE • •
•
8
21
0
2
6
10
10. Selected analytical data: Sch 56592: mp 170–172 ꢁC. ½aꢁD
DAYS
1
ꢀ23.3 (c 1, CHCl3). H NMR (CDCl3, 400 Hz) d 8.11 (s,
1H), d 7.80 (s, 1H), d 7.66 (s, 1H), d 7.43 (m, 2H), d 7.39
(m, 1H), d 7.03 (m, 2H), d 6.95 (m, 2H), d 6.86 (m, 1H), d
6.83 (m, 1H), d 6.78 (m, 2H), d 4.65–4.51 (d, J = 14.5 Hz,
d, J = 14.5 Hz, 2H), d 4.11–3.78 (dd, J = 8.7, 7.4 Hz, dd,
J = 8.7, 6.8 Hz, 2 H), d 4.06 (m, 1H), d 4.02 (m, 1H), d
3.70–3.62 (dd, J = 9.0, 5.6 Hz, dd, J = 9.0, 7.3 Hz, 2H), d
3.38 (m, 4H), d 3.24 (m, 4H), d 3.08 (d, J = 9.0 Hz, 1H), d
2.61 (m, 1H), d 2.55–2.08 (m, J = 12.7, 7.9, 2.5 Hz, dd,
J = 12.7, 8.3 Hz, 2H), d 2.00–1.89 (mm, 2H), d 1.22 (d,
J = 6.3 Hz, 3H), d 0.94 (t, J = 7.4 Hz, 3H). HR-FABMS
calcd for C37H43N8O4F2: 701.3375. Found: 701.3378
(M+H)+.
Chart 4. Aspergillus fumigatus, ND159 pulmonary infection in mice.
In summary, based on previous leads, a series of hydrox-
ylated potential antifungal agents were synthesized. All
alcohols proved to be extremely potent in vitro. A select-
ed number of these analogues were evaluated in vivo
and based on an overall superior profile, Sch 56592
was selected for clinical studies. Extension of this work
including the evaluation of water-soluble prodrugs of
posaconazole will be published elsewhere.
11. Selected analytical data: Sch 56984: [a]D ꢀ23.65 (c 1,
1
CHCl3). H NMR (CDCl3, 300 Hz) d 8.11 (s, 1H), d 7.80
References and notes
(s, 1H), d 7.63 (s, 1H), d 7.40 (m, 2H), d 7.39 (m, 1H), d
7.03 (m, 2H), d 6.94 (br, 2H), d 6.84 (m, 1H), d 6.84 (m,
1H), d 6.78 (m, 2H), d 4.65–4.51 (d, J = 14.4 Hz, d,
J = 14.4 Hz, 2H), d 4.28–4.19 (m, 1H), d 4.28–4.19 (m,
1H), d 4.11–3.77 (mm, 2H), d 3.63 (mm, 2H), d 3.36 (m,
4H), d 3.23 (m, 4H), d 2.61 (m, 1H), d 2.54–2.07 (m,
J = 12.5, 7.8, 2.3 Hz, dd, J = 12.5, 7.7 Hz, 2H), d 1.42 (d,
J = 6.9 Hz, 3H), d 1.24 (d, J = 6.2 Hz, 3H). MS m/z: 687.5
(M+H)+.
1. (a) Viscoli, C.; Girmenia, A.; Marinus, A. Clin. Infect. Dis.
1999, 28, 1071; (b) Rangel-Frausto, M. S.; Wiblin, T.;
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1992, 36, 498.
14. Methods. Drugs were administered orally to mice (Charles
River CF1 white males, ca. 20 g) which had been fasted for
18 h. Six mice were used per time point. The AUC was
calculated from 0 to 24 h. The compounds were prepared
in methyl cellulose (0.4%) containing polysorbate 80
(0.5%) and NaCl (0.9%), except for Sch 51048, which
was prepared in 40% hydroxypropyl-b-cyclodextrin.
HPLC was used to determine the drug concentrations in
serum.
15. Methods. Drugs were administered orally to cynomolgus
monkeys (weight range 5.9–7.3 kg). The compounds were
prepared in methyl cellulose (0.4%) containing polysor-
bate 80 (0.5%) and NaCl (0.9%), except for Sch 51048,
which was prepared in 40% hydroxypropyl-b-cyclodextrin.
HPLC was used to determine the drug concentrations in
serum.
2. (a) De Beule, K.; Van Gestel, J. Drugs 2001, 61, 27; (b)
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Kate, M. T.; Bakker-Woudenberg, I. A. J. M. Antimicrob.
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ama, K.; Maesaki, S.; Miyazaki, Y.; Tanaka, E.; Takiz-
awa, T.; Moribe, K.; Kazunori, T.; Tashiro, T.; Kohno, S.
Antimicrob. Agents Chemother. 1998, 42, 40.
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5. Fung-Tomc, J. C.; Huczko, E.; Minassian, B.; Bonner, D.
P. Antimicrob. Agents Chemother. 1998, 42, 313.
6. (a) Lovey, R.; Saksena, A.; Girijavallabhan, V.; Blundell,
P.; Guzik, H.; Loebenberg, D.; Parmegiani, R.; Cacciapu-
oti, A. Bioorg. Med. Chem. Lett. 2002, 12, 1739; (b)
Saksena, A.; Girijavallabhan, V.; Wang, H.; Liu, Y.-T.;
Pike, R.; Ganguly, A. Tetrahedron Lett. 1996, 37, 5657; (c)
Saksena, A.; Girijavallabhan, V.; Lovey, R.; Pike, R.;
Wang, H.; Ganguly, A.; Morgan, B.; Zaks, A.; Puar, M.
Tetrahedron Lett. 1995, 3, 787; (d) Saksena, A.; Girijaval-
labhan, V.; Lovey, R.; Desai, J.; Pike, R.; Jao, E.; Wang,
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16. Methods. Immunocompromised mice (c-irradiated,
500 rads, 3 days prior to infection) were infected intrave-
nously with 1 · 106 CFU/mouse of C. albicans C72.

190
F. Bennett et al. / Bioorg. Med. Chem. Lett. 16 (2006) 186–190
Treatment (oral) began 4 h postinfection and continued
of, and the day after inhalation infection (30 s exposure) of
A. fumigatus ND159 conidia in an inhalation flask.
Treatment (oral) began 24 h postinfection and continued
once daily for 4 days. The compounds were prepared in
methyl cellulose (0.4%) containing polysorbate 80 (0.5%)
and NaCl (0.9%). The mice were Charles River CF1 white
males.
once daily for 4 days. The compounds were prepared in
methyl cellulose (0.4%) containing polysorbate 80 (0.5%)
and NaCl (0.9%). The mice were Charles River CF1 white
males.
17. Methods. The mice were immunocompromised with cor-
tisone acetate (100 mg/kg, SC) on the day before, the day