Synthesis of new penicillin derivatives as drug-like molecules for biological screening

Article abstract of DOI:10.1016/j.cclet.2014.09.008

Chemical modification of penicillin β-lactam ring was made. Six thiazolidine amides were produced through N4-C7 β-lactam ring opening of penicillin V methyl ester with various aliphatic, aromatic, and heterocyclic primary amines. Five 8-hydroxypenillic ac

Full text of DOI:10.1016/j.cclet.2014.09.008

G Model
CCLET 3089 1–5
Chinese Chemical Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
2
Original article
3
4
Synthesis of new penicillin derivatives as drug-like molecules for
biological screening
a
b
Q1 Chun-Jing Liu a, , Dinah Dutta , Lester Mitscher
*
5
6
7
a Higuchi Biosciences Center, The University of Kansas, Lawrence KS66045, USA
b Department of Medicinal Chemistry, The University of Kansas, Lawrence KS66045, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
Chemical modification of penicillin
b-lactam ring was made. Six thiazolidine amides were produced
Received 22 May 2014
Received in revised form 8 July 2014
Accepted 22 August 2014
Available online xxx
through N4-C7
heterocyclic primary amines. Five 8-hydroxypenillic acid derivatives with side chains of methyl, propyl,
benzyl, and diethylaminoethyl groups were yielded via -lactam ring rearrangement from 6-
aminopenicillanic acid (6-APA). Parallel synthetic methods were used for the alkylation of 8-
hydroxypenillic acid and -lactam ring opening of penicillin V methyl ester. The biological activities of
b-lactam ring opening of penicillin V methyl ester with various aliphatic, aromatic, and
b
b
Keywords:
the compounds were evaluated.
Penicillin
ß 2014 Chun-Jing Liu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights
Rearrangement
reserved.
b-Lactam antibiotics
Nucleophilic ring opening
8
9
1. Introduction
2. Experimental
30
Column chromatography was carried out by employing silica 31
gel (230–400 mesh). Thin-layer chromatography (TLC) was 32
performed on a silica gel w/uv254 uniplateTM. Anhydrous organic 33
solvents were purchased. Parallel synthesis was conducted on 34
Mettler Toledo MiniBlock and MiniBlock XT. Melting points were 35
determined using a Barnstead International MET-TEMP1 capillary 36
melting point apparatus model 1001D-120VAC. IR spectra were 37
measured with a Perkin ElmerTM Spectrum One FT-IR spectrome- 38
ter. 1H NMR and 13C NMR spectra were recorded on a 400 MHz 39
spectrometer (400 and 100 MHz, respectively), or a 500 MHz 40
spectrometer (500 and 125.5 MHz, respectively). Abbreviations 41
were as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, 42
multiplet. High-resolution mass spectrometry (HRMS) spectra 43
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13
14
15
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17
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25
26
27
28
29
Penicillins are
gram-negative and anaerobic organisms by blocking peptidogly-
can biosynthesis [1–8]. -Lactams are 4-memebered cyclic amides,
depicted in 6-aminopenicillanic acid (6-APA) in Fig. 1 [9,10]. Vari-
ous bonds in -lactam can undergo cleavage to give acyclic
systems or result into rearranged cyclic derivatives [11–15]. Cleav-
age of -lactam bond (N4-C7) and conversion of -lactam ring into
other cyclic systems have been studied [16–18]. Nucleophilic
opening of -lactam bond using primary amine forms
thiazolidine amides [19,20].
In this paper, chemical modification of penicillin
was undertaken. -Lactam ring rearrangement of 6-APA produced
8-hydroxypenillic acid derivatives with side chains of methyl,
propyl, benzyl, diethylaminoethyl, and 2-(bromomethyl)ben-
zo[d]thiazole groups. b-Lactam ring opening of penicillin V methyl
ester yielded thiazolidine amides with p-methoxybenzylamine,
anisidine, benzyl amine, thiophene methylamine, cyclopropane
methyl amine, and nonyl amine. Parallel synthetic methods
were developed for esterification of 8-hydroxypenillic acid and
b-lactam antibiotics to kill many gram-positive,
b
b
b
b
b
a
b-lactam ring
b
were obtained on a double-focusing mass spectrometer.
44
2.1. Procedure for synthesis of intermediate penicillin V
45
Potassium (2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenoxyaceta- 46
mido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate (penicil- 47
lin V). To a cooled and stirred solution of 2.76 g (12.5 mmol) of 48
6-APA in 60 mL of water containing 5.25 g (62.5 mmol) of sodium 49
bicarbonate, a solution of 2.76 g (16.2 mmol) phenoxyacetyl 50
chloride in 5 mL of acetone was added in one minute. The 51
resulting mixture was stirred vigorously during 20 min while the 52
temperature was kept at 10–15 8C. The clear solution was 53
b
-lactam ring opening of penicillin V methyl ester.
*
Corresponding author.
E-mail address: cjliu2@gmail.com (C.-J. Liu).
http://dx.doi.org/10.1016/j.cclet.2014.09.008
1001-8417/ß 2014 Chun-Jing Liu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Please cite this article in press as: C.-J. Liu, et al., Synthesis of new penicillin derivatives as drug-like molecules for biological screening,
Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.09.008

G Model
CCLET 3089 1–5
2
C.-J. Liu et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
(2R,4S)-Methyl 2-((R)-2-(4-methoxyphenylamino)-2-oxo-1-
(2-phenoxyacetamido)ethyl)-5,5-dimethylthiazolidine-4-car-
boxylate (2b): yield 62%; 1H NMR (400 MHz, CDCl3):
8.59 (s, 1H),
7.67 (d, 1H, J = 6.4 Hz), 7.42 (m, 2H), 7.32 (m, 2H), 6.96 (m, 1H), 6.95
(m, 2H), 6.85 (m, 2H), 5.36 (m, 1H), 4.74 (m, 1H), 4.57 (s, 2H), 3.80
(s, 3H), 3.75 (s, 3H), 3.64 (s, 1H), 1.55 (s, 3H), 1.24 (s, 3H); 13C NMR
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
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135
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137
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139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
d
(100 MHz, CDCl3): d 169.8, 169.3, 166.6, 157.1, 156.7, 129.5, 129.8,
Fig. 1. Chemical structure of 6-aminopenicillanic acid (6-APA).
122.2, 121.8, 114.8, 114.2, 72.8, 67.3, 65.3, 58.0, 57.3, 55.5, 52.4,
26.8, 26.5; HRMS (FAB) calcd. for C24H30N3O6S [M+H]+: m/z
488.1855; found: 488.1849.
(2R,4S)-Methyl 5,5-dimethyl-2-((R)-2-oxo-1-(2-phenoxyace-
tamido)-2-(thiophen-3-ylmethylamino)ethyl)thiazolidine-4-car-
boxylate (2c): yield: 63%; 1H NMR (400 MHz, CDCl3):
d 7.61 (d, 1H,
J = 7.56 Hz), 7.32 (m, 3H), 7.18 (s, 1H), 7.01 (m, 2H), 6.91 (m, 3H),
5.24 (d, 1H, J = 4.9 Hz), 4.72 (m, 1H), 4.62 (m, 1H), 4.52 (m, 1H), 4.50
(m, 2H), 3.73 (s, 3H), 3.56 (s, 2H), 1.47 (s, 3H), 1.18 (s, 3H); 13C NMR
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
extracted twice with 15 mL portions of methyl isobutyl ketone
(MIBK). The clear aqueous solution was cooled to 5–10 8C and
acidified to pH 2 with a cold 5.0 mol/L sulfuric acid solution. The
acidified aqueous solution was extracted with 50 mL MIBK twice.
The MIBK extract was separated, washed with cold water, and
dried for 10 min over anhydrous sodium sulfate. After filtration,
10 mL of a 25% solution of potassium 2-ethylhexanoate in butanol
was added. The white crystalline material was collected by
filtration, washed on the filter with dry acetone and dried in
vacuum, yield 3.5 g (80%) penicillin V as a white solid. Mp:
(100 MHz, CDCl3): d 169.8, 168.9, 168.4, 157.1, 140.2, 129.7, 126.9,
126.2, 125.2, 122.1, 114.8, 72.5, 67.2, 65.5, 58.0, 56.7, 52.2, 38.2,
26.6, 26.5; HRMS (FAB) calcd. for C22H28N3O5S2 [M+H]+: m/z
478.1470; found: 478.1475.
210–211 8C (dec.). 1H NMR (400 MHz, DMSO-d6):
d
8.42 (d, 1H,
(2R,4S)-Methyl 2-((R)-2-(benzylamino)-2-oxo-1-(2-phenox-
yacetamido)ethyl)-5,5-dimethylthiazolidine-4-carboxylate (2d):
J = 8.0 Hz), 7.27 (m, 2H), 6.92 (m, 3H), 5.42 (dd, 1H, J = 8.0 Hz,
4.0 Hz), 5.40 (d, 1H, J = 4.0 Hz), 4.62 (d, 2H, J = 2.2 Hz), 3.88 (s, 1H),
yield 54%; 1H NMR (400 MHz, CDCl3):
d 7.48 (d, 1H, J = 7.4 Hz),
1.52 (s, 3H), 1.46 (s, 3H); 13C NMR (100 MHz, DMSO-d6):
d
172.8,
7.46 (d, 1H, J = 8.0 Hz), 7.21 (m, 2H), 7.20 (m, 2H), 7.03 (m, 1H), 6.99
(m, 2H), 6.86 (m, 2H), 5.36 (m, 1H), 5.13 (m, 1H), 4.68 (m, 1H), 4.64
(m, 1H), 4.57 (m, 2H), 4.23 (m, 1H), 3.77 (s, 3H), 3.73 (s, 3H), 1.48 (s,
3H), 1.18 (s, 3H); 13C NMR (100 MHz, CDCl3):
d 172.8, 169.8, 168.3,
169.0, 168.1, 158.1, 130.0, 121.7, 115.0, 74.6, 67.3, 66.7, 65.0, 57.8,
32.7, 27.8; HRMS (FAB) calcd. for C16H18KN2O5S [M+H]+: m/z
389.0584; found: 389.0995.
156.8, 137.8, 129.8, 128.6, 127.4, 122.0, 115.6, 74.9, 73.0, 72.4, 65.1,
58.0, 56.8, 52.3, 43.6, 26.5, 18.9; HRMS (FAB) calcd. for
71
72
2.2. Procedure for synthesis of intermediate penicillin V methyl ester
(1)
C
25H32N3O6S [M+H]+: m/z 5 02.2011; found: 502.1992.
(2R,4S)-Methyl 2-((R)-2-(cyclopropylamino)-2-oxo-1-(2-phe-
73
74
75
76
77
78
79
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81
82
83
84
85
86
(2S,5R,6R)-Methyl 3,3-dimethyl-7-oxo-6-(2-phenoxyaceta-
mido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate (1):
penicillin V (388 mg, 1.0 mmol) was suspended in 10 mL of
dimethylformamide (DMF). Methyl iodide (1.4 g, 12.0 mmol) was
added and stirred for 1 h at room temperature. After most of
the solvent was removed under reduced pressure, the mixture
was loaded on silica gel column for chromatography with
EtOAc/hexane (1:9) as an eluent to yield product 1 (65%) as a
noxyacetamido)ethyl)-5,5-dimethylthiazolidine-4-carboxylate
(2e): yield 64%; 1H NMR (400 MHz, CDCl3):
7.55 (d, 1H,
d
J = 7.7 Hz), 7.29 (m, 2H), 7.01 (m, 2H), 6.80 (m, 1H), 5.17 (d, 1H,
J = 8.0 Hz), 4.51 (s, 1H), 4.50 (s, 2H), 3.75 (s, 3H), 3.66 (s, 1H), 2.70
(m, 1H), 1.53 (s, 3H), 1.19 (s, 3H), 0.73 (m, 2H), 0.49 (m, 2H); 13C
NMR (100 MHz, CDCl3):
d 170.1, 169.8, 168.9, 157.2, 129.7, 122.1,
114.8, 72.7, 67.2, 65.8, 58.3, 56.8, 52.3, 27.0, 26.6, 22.7, 6.5, 6.4;
HRMS (FAB) calcd. for C20H28N3O5S [M+H]+: m/z 422.1749; found:
422.1739.
(2R,4S)-Methyl 5,5-dimethyl-2-((R)-2-(nonylamino)-2-oxo-1-
(2-phenoxyacetamido)ethyl)thiazolidine-4-carboxylate (2f):
yield 58%; 1H NMR (400 MHz, CDCl3):
d 7.58 (d, 1H, J = 8 Hz),
7.24 (m, 2H), 6.98 (m, 1H), 6.90 (m, 2H), 6.84 (m, 1H), 5.15 (m, 1H),
4.57 (m, 1H), 4.48 (s, 1H), 3.71 (s, 3H), 3.68 (s, 1H), 3.51 (m, 1H),
3.17 (m, 2H), 1.51 (s, 3H), 1.45 (m, 2H), 1.21 (m, 14H), 1.17 (s, 3H),
0.83 (m, 3H); 13C NMR (100 MHz, CDCl3):
d 169.8, 168.8, 168.7,
157.2, 129.6, 122.0, 114.8, 72.6, 67.3, 66.0, 58.3, 57.0, 52.1, 39.7,
31.8, 29.5, 29.4, 29.3, 29.2, 27.1, 26.9, 26.7, 22.6, 14.1; HRMS
(FAB) calcd. for C26H42N3O5S [M +H]+: m/z 508.2845; found:
508.2828.
colorless oil. 1H NMR (400 MHz, CDCl3):
1H), 6.93 (m, 2H), 5.75 (d, 1H, J = 4.0 Hz), 5.60 (d, 1H, J = 4.0 Hz),
4.57 (s, 2H), 4.49 (s, 1H), 3.80 (s, 3H), 1.61 (s, 3H), 1.51 (s, 3H); 13
NMR (100 MHz, CDCl3): 173.1, 168.1, 167.8, 156.9, 129.8, 122.4,
d 7.32 (m, 2H), 7.04 (m,
C
d
114.8, 70.5, 67.7, 67.1, 64.8, 58.0, 52.5, 31.8, 26.9; HRMS (FAB)
calcd. for C17H21N2O5S [M+H]+: m/z 365.1170; found: 365.1194.
87
2.3. Procedure for synthesis of thiazolidine derivatives 2a–2f
88
89
90
91
92
93
94
95
(2R,4S)-Methyl 2-((R)-2-(4-methoxybenzylamino)-2-oxo-1-(2-
phenoxyacetamido)ethyl)-5,5-dimethylthiazolidine-4-carboxylate
(2a):penicillin V methyl ester(1, 182.0 mg, 0.5 mmol) was takenin a
round-bottomed flask and 15 mL of dry methylene chloride was
added. Benzyl amine (108.0 mg, 1.0 mmol) was added at room
temperature and the mixture was stirred overnight. Water was
added into the mixture and the mixture was extracted with
methylene chloride (2 Â 20 mL). After washing with brine, the
organic layer was dried over NaSO4, concentrated and purified by
column chromatography with EtOAc/hexane (1:1) as the eluent to
2.4. Procedure for synthesis of intermediate disodium salt of 8-
157
158
hydroxypenillic acid (3)
Disodium 3,3-dimethyl-8-oxo-4-thia-1,7-diazabicyclo[3.3.0]
octane-2,6-dicarboxylic acid (3): compound 3 was prepared in
the method modified from Johnson and Hardcastle [17]. 4.5 g of
6-APA was dissolved in 100 mL of water containing 3.5 g
(2.0 equiv.) of sodium bicarbonate. Carbon dioxide from dry ice
was bubbled through the stirred mixture at room temperature for
24 h. The concentrated aqueous solution was then lyophilized
overnight to yield 6.2 g (90%) of the product 3 as a pale yellow
159
160
161
162
163
164
165
166
167
168
169
96
97
98
yield product 2a (55%) as a semi-solid. 1H NMR (400 MHz, CDCl3):
d
99
7.59 (d, 1H, J = 7.36 Hz), 7.33–7.29 (m, 5H), 7.01 (m, 2H), 6.93 (m,
100
101
102
103
104
105
2H), 5.27 (s, 1H), 4.65 (m, 1H), 4.61 (m, 1H), 4.51 (s, 2H), 4.37 (dd, 1H,
J = 5.9, 14.7 Hz), 3.75(s, 3H), 3.55(s, 2H), 1.48(s, 3H), 1.20(s, 3H); 13
C
NMR (100 MHz, CDCl3):
d 169.9, 168.9, 168.5, 157.1, 137.7, 129.7,
128.8, 127.9, 127.6, 122.1, 114.8, 72.6, 67.2, 65.4, 58.0, 56.8, 52.3,
43.8, 26.6, 26.4; HRMS (FAB) calcd. for C24H30N3O5S [M+H]+: m/z
472.1906; found: 472.1910.
powder. Mp 228–230 8C (dec.). 1H NMR (400 MHz, D2O):
1H, J = 2.0 Hz), 4.15 (s, 1H), 4.13 (d, 1H, J = 2.0 Hz), 1.47 (s, 3H), 1.42
(s, 3H); 13C NMR (125 MHz, D2O):
177.5, 175.9, 164.4, 73.6, 69.4,
d 5.44 (d,
d
Please cite this article in press as: C.-J. Liu, et al., Synthesis of new penicillin derivatives as drug-like molecules for biological screening,
Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.09.008

G Model
CCLET 3089 1–5
C.-J. Liu et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
3
170
171
59.5, 57.7, 31.5, 25.8; HRMS (FAB) calcd. for C9H11N2Na2O5S
added to a vigorously stirred solution of 4a (200 mg, 0.7 mmol) in 232
DMF and stirring was continued for 3 h at40–45 8C. Themixture was 233
filtered, and the filtrate was diluted with water and extracted with 234
diethyl ether. The extracts were dried over anhydrous Na2SO4 and 235
the organic solvent was evaporated. The crude product was purified 236
by flash column chromatography with EtOAc/hexane (1:2) as an 237
eluent to obtain a white semi-solid 5a. Yield 49%; IR: 2954, 1720, 238
[M+H]+: m/z 305.0184; found: 305.0174.
172
173
2.5. Procedure for alkylation of 8-hydroxypenillic acid to synthesize
compounds 4a–4d
174
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176
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182
183
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226
(3S,7R,7aR)-Dimethyl 2,2-dimethyl-5-oxohexahydroimi-
dazo[5,1-b]thiazole-3,7-dicarboxylate (4a): compound 4a was
prepared in the method of Johnson and Hardcastle [17]. The
synthesis of the dimethyl ester was initiated by dissolving the
disodium salt 3 (2.0 g, 6.6 mmol) in DMF (50 mL) and methyl
iodide (3.0 mL, 48.1 mmol) was added and stirred at room
temperature for 12 h, water was added to the reaction mixture
and extracted with (3 Â 100 mL) diethyl ether, dried and
concentrated. The crude product was purified by flash silica gel
column chromatography using EtOAc/hexane (1:1) as an eluent.
Pure compound 4a (1.14 g, 60%) was isolated as a white solid. Mp:
1418, 1369, 1206 cmÀ1; 1H NMR (400 MHz, CDCl3):
d7.36–7.25 (m, 239
5H), 5.63 (d, 1H, J = 1.2 Hz), 5.06 (d, 1H, J = 15.2 Hz), 4.83 (s, 1H), 4.21 240
(d, 1H, J = 15.2 Hz), 4.08 (d, 1H, J = 1.3 Hz), 1.57 (s, 3H), 1.49 (s, 3H); 241
13CNMR(100 MHz, CDCl3):
d
169.6, 169.5,160.1, 135.3,128.8, 129.2, 242
127.9, 71.3, 67.0, 60.6, 58.3, 52.9, 52.0, 46.3, 33.9, 26.6; HRMS(FAB) 243
calcd. for C19H22N3O5S2 [M+H]+: m/z 379.1327; found: 379.1334.
244
(3S,7R,7aR)-Dimethyl 6-(benzo[d]thiazol-2-ylmethyl)-2,2-di- 245
methyl-5-oxohexahydroimidazo[5,1-b]thiazole-3,7-dicarboxylate 246
(5b): yield 40%; 1H NMR (400 MHz, CDCl3):
d 7.99 (d, 1H, 247
J = 8.2 Hz), 7.89 (d, 1H, J = 8.0 Hz), 7.48 (t, 1H, J = 8.0 Hz), 7.43 (t, 248
1H, J = 8.0 Hz), 5.71 (d, 1H, J = 1.7 Hz), 5.38 (d, 1H, J = 16.6 Hz), 4.83 249
(s, 1H), 4.77 (d, 1H, J = 16.5 Hz), 4.51 (d, 1H, J = 1.7 Hz), 3.81 (s, 3H), 250
164–166 8C. 1H NMR (400 MHz, CDCl3):
J = 1.48 Hz), 4.70 (s, 1H), 4.35 (d, 1H, J = 1.52 Hz), 3.85 (s, 3H), 3.78
(s, 3H), 1.57 (s, 3H), 1.49 (s, 3H); 13C NMR (100 MHz, CDCl3):
d 5.89 (s, 1H), 5.78 (d, 1H,
d
3.79 (s, 3H), 1.64 (s, 3H), 1.50 (s, 3H); 13C NMR (100 MHz, CDCl3):
d
251
170.2, 169.3, 161.2, 70.8, 68.2, 58.6, 58.3, 53.2, 52.1, 33.7,
26.4. HRMS (FAB) calcd for C11H17N2O5S [M+H]+: m/z 289.0788;
found 289.0864.
169.3, 166.7, 159.7, 153.0, 135.4, 126.3, 125.4, 123.2, 121.9, 71.2, 252
66.9, 61.5, 58.4, 53.1, 52.1, 44.9, 34.0, 26.7; HRMS (FAB) calcd. for 253
C
18H22N3O5S2 [M+H]+: m/z 436.1001; found: 436.1014.
254
(3S,7R,7aR)-Dipropyl 2,2-dimethyl-5-oxohexahydroimi-
dazo[5,1-b]thiazole-3,7-dicarboxylate (4b): yield 62%; mp
3. Results and discussion
255
119–120 8C; 1H NMR (400 MHz, CDCl3):
d 6.20 (s, 1H), 5.78 (s,
1H), 4.69 (s, 1H), 4.33 (s, 1H), 4.16 (d, 2H, J = 6.72 Hz), 4.10 (dd, 2H,
J = 6.8, 13.5 Hz), 1.66 (m, 4H), 1.55 (s, 3H), 1.48 (s, 3H), 0.95 (q, 6H,
3.1. Synthesis of thiazolidine amides through opening the
ring of penicillin V
b
-lactam 256
257
J = 8.0 Hz); 13C NMR (100 MHz, CDCl3):
d 169.9, 168.9, 161.5, 70.8,
68.4, 67.9, 66.9, 58.6, 58.5, 34.0, 26.4, 21.8, 10.5, 10.2; HRMS (FAB)
calcd. for C15H25N2O5S [M+H]+: m/z 345.1484; found: 345.1496.
(3S,7R,7aR)-Dibenzyl 2,2-dimethyl-5-oxohexahydroimi-
dazo[5,1-b]thiazole-3,7-dicarboxylate (4c): yield 63%; mp
Treatment of penicillin V with methyl iodide in DMF was 258
carried out. Penicillin V methyl ester (1) as an intermediate was 259
isolated and purified. With compound 1 available we developed an 260
efficient procedure for generating a number of penicillin deriva- 261
tives. Based on a parallel synthesis strategy, our method was to 262
133–134 8C; 1H NMR (400 MHz, CDCl3):
d 7.35–7.28 (m, 10H),
5.95 (s, 1H), 5.83 (d, 1H, J = 1.4 Hz), 5.22 (m, 2H), 5.17 (s, 2H), 4.74
(s, 1H), 3.37 (d, 1H, J = 1.36 Hz), 1.54 (s, 3H), 1.42 (s, 3H); 13C NMR
synthesize penicillin derivatives through opening the
ring of intermediate 1 with amines, which attacks the carbonyl 264
group of -lactam ring to form thiazolidine amides (Scheme 1). 265
b-lactam 263
(100 MHz, CDCl3):
d
169.6, 168.7, 161.3, 134.9, 134.7, 128.8, 128.7,
b
128.6, 128.5, 70.7, 68.3, 68.0, 67.2, 58.8, 58.4, 33.9, 26.4;
HRMS(FAB) calcd. for C23H25N2O5S [M+H]+: m/z 441.1484; found:
441.1485.
This synthetic approach was developed amenable to automation, 266
enabling us to generate tens of compounds in a week using a 267
Mettler Toledo MiniBlock Suite for library preparation and 268
compound handling. In parallel, reaction of compound 1 with 269
various aromatic, aliphatic and heterocyclic amines was carried 270
out in six reactors, respectively. Six products (2a–2f) were 271
produced simultaneously. They were purified and characterized 272
(3S,7R,7aR)-Bis(2-(diethylamino)ethyl) 2,2-dimethyl-5-oxohex-
ahydroimidazo[5,1-b]thiazole-3,7-dicarboxylate (4d): to a suspen-
sion of N,N-diethylaminoethyl bromide hydrobromide (1.05 g,
4.0 mmol) in 15 mL of dry DMF was added sodium bicarbonate
(1.26 g, 15 mmol). The suspension was stirred at room temperature
for 2 h, then disodium salt of 8-hydroxypenillic acid 3 (500 mg,
1.6 mmol) was added. The reaction mixture was allowed to stir at
room temperature overnight. Water (10 mL) was added to the
reaction mixture and extracted with diethyl ether (3 Â 50 mL). The
organic layer was dried over Na2SO4 and concentrated to obtain a
colorless semi-solid 4d 189 mg (40%). IR: 3236, 3104, 2972, 2807,
by 1H NMR and 13C NMR spectra and HRMS.
273
3.2. Synthesis of 8-hydroxypenillic acid derivatives through
ring rearrangement of 6-APA
b
-lactam 274
275
The rearrangement of the
b-lactam ring started from 6-APA 276
following our method (Scheme 2) modified from Johnson and 277
Hardcastle [17]. Treatment of 6-APA with carbon dioxide was 278
carried out in sodium bicarbonate aqueous solution. 6-APA was 279
dissolved in water containing sodium bicarbonate. Carbon dioxide 280
from a dry ice source was bubbled through the stirred mixture. 281
The concentrated aqueous solution was then lyophilized to obtain 282
the disodium salt of 8-hydroxypenillic acid in high yield. The 283
8-hydroxypenillic acid (isolated as the disodium salt by lyophiliza- 284
tion) was characterized by 1H NMR and 13C NMR spectroscopy and 285
HRMS. The NMR spectra of the disodium salt of 8-hydroxypenillic 286
acid were well resolved and displayed no unassigned signals of 287
significant intensity. The similar 1H NMR chemical shifts have been 288
previously observed [18,21]. Furthermore our 13C NMR chemical 289
.
1731, 1613, 1456, 1382, 1176, 1122 cmÀ1 1H NMR (400 MHz,
CDCl3): 6.65(s, 1H), 5.73(d, 1H, J = 1.58 Hz), 4.64(s, 1H), 4.32(d, 1H,
d
J = 1.56 Hz), 4.24 (t, 2H, J = 5.64 Hz), 4.17 (t, 2H, J = 6.0 Hz),2.74–2.67
(m, 4H), 2.60–2.51 (m, 8H), 1.53 (s, 3H), 1.47 (s, 3H), 1.02–0.97 (m,
12H); 13C NMR (100 MHz, CDCl3):
d 169.9, 168.8, 161.5, 70.8, 68.3,
64.0, 58.3, 58.5, 51.0, 50.8, 47.3, 47.2, 33.7, 26.4, 11.9, 11.6; HRMS
(FAB) calcd. for C21H39N4O5S [M+H]+: m/z 459.2641; found:
459.2640.
227
228
2.6. Procedure for alkylation of 8-hydroxypenillic acid methyl ester at
position N-7 to synthesize compounds 5a and 5b
229
230
231
(3S,7R,7aR)-Dimethyl 6-benzyl-2,2-dimethyl-5-oxohexahydroi-
midazo[5,1-b]thiazole-3,7-dicarboxylate (5a): benzyl bromide
(2.05 g, 1.2 mmol) and anhydrous K2CO3 (2.5 mg, 1.8 mmol) were
shifts are the same as the previous report [18,21].
Using a parallel synthetic strategy, alkylation of 8-hydroxype- 291
nillic acid was initiated on MiniBlock by treatment of its disodium 292
290
Please cite this article in press as: C.-J. Liu, et al., Synthesis of new penicillin derivatives as drug-like molecules for biological screening,
Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.09.008

G Model
CCLET 3089 1–5
4
C.-J. Liu et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
Scheme 1. Ring opening of
b-lactams of penicillin V methyl ester.
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
salt 3 with various aliphatic and aromatic halides as shown in
Scheme 3. Disodium salt 3 was dissolved in DMF, and methyl
iodide or benzyl bromide or propane iodide was added into the
solution. The crude residues were purified to obtain pure products
4a–4c as white solids in moderate yields. Since N,N-diethylami-
noethyl bromide hydrobromide was employed for the synthesis of
4d, excess sodium bicarbonate was added first into the solution to
quench the hydrobromide acid. Compound 4d was isolated by
extracting with diethyl ether from the water solution of the
Furthermore, alkylation of 8-hydroxypenillic acid methyl ester
310
311
312
313
314
315
316
317
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321
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323
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342
(4a) was carried out at its N-7 position with benzyl bromide or
2-(bromomethyl)benzo[d]thiazole using potassium carbonate as
base in DMF (Scheme 4). Benzyl bromide and anhydrous potassium
carbonate were added to a solution of 4a in DMF and the mixture
was stirred. The crude product was purified to obtain a pure
product 5a as a white semi-solid in modest yield. Similar
procedure was proceeded for the synthesis of 5b by using
2-(bromomethyl)benzo[d]thiazole as an alkylation reagent. Com-
pounds 5a and 5b were identified by 1H NMR and 13C NMR and
HRMS. In the 1H NMR spectra of compound 5a, the chemical shift of
the methylene in the benzyl group supported the benzyl alkylation
reaction mixture. Products (4a–4d) were confirmed by 1H and 13
NMR spectra and HRMS. In the 1H NMR spectra of compound 4b,
two 2-proton multiplet peaks of methylene groups at 4.17 were
indicative of the formation of propyl esters at C3 and C6 positions.
The complex patterns at 7.38 and 5.16 affirmed the presence of
benzyl methyl esters in the compound 4c. For product 4d, the
patterns at 4.25, 4.17, 2.74, 2.60, 0.97 confirmed the formation of
C
d
at N-7 position, and the signals from its
b-lactam protons were
d
identical in position and pattern with those in the spectrum of the
starting penillic acid methyl ester 4a. For product 5b, the complex
patterns of benzo[d]thiazol-2-ylmethyl group confirmed the
achievement of alkylation at N-7 position by 2-(bromomethyl)-
benzo[d]thiazole.
In the past six decades, numerous penicillin derivatives were
synthesized [1–11] through chemical modification. This led to
marketing of several antibiotics [3–10]. According to our SciFinder
d
diethylaminoethyl esters.
search, six amides from
b-lactam ring opening and five esters by
penicillin -lactam ring rearrangement in this work are new. The
b
compounds were deposited into NIH Small Molecule Repository.
They were screened and their biological results were deposited
into PubChem [22]. The biological activity can be found by using
compound identification (CID) numbers. Compound 2a (CID
24747544) inhibits human tyrosyl-DNA phosphodiesterase 1
(TDP1) [22]; compound 2e (CID 24747364) modulates the
interaction between C-terminal C-end Rule (CendR) and neuropi-
lin-1 (NRP-1) [22]; compound 2f (CID 24747549) inhibits KCNQ2
potassium channels [22]; compound 4b (CID 24747497) enhances
the survival of human induced plaripotent stem cells [22];
Scheme 2. Synthesis of disodium salt of 8-hydroxypenillic acid from 6-APA.
Scheme 3. Synthesis of 8-hydroxypenillic acid esters.
Scheme 4. Alkylation of 8-hydroxypenillic acid methyl ester at N-7 position.
Please cite this article in press as: C.-J. Liu, et al., Synthesis of new penicillin derivatives as drug-like molecules for biological screening,
Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.09.008

G Model
CCLET 3089 1–5
C.-J. Liu et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
5
[8] G.H. Hakimelahi, K.S. Shia, C. Xue, et al., Design, synthesis, and biological 374
evaluation of
343
344
compound 4c (CID 24747437) can identify antagonists of the
human trace amine associated receptor 1 (TAAR1) [22].
a
series of b-lactam-based prodrugs, Bioorg, Med. Chem. 10 375
(2002) 3489–3498.
376
377
[9] T.L. Gilchrist, Heterocyclic Chemistry, 2nd ed., Longman Press, Harlow, 1997.
[10] S. Wolfe, S. Ro, C.K. Kim, Z. Shi, Synthesis and decarboxylation of D2-cephem-4 378
345
4. Conclusion
4-dicarboxylic acids, Can. J. Chem. 79 (2001) 1238–1258.
379
[11] B. Alcaide, P. Almendros, C. Aragoncillo, b-Lactams: versatile building blocks for 380
the stereoselective synthesis of non b-lactam products, Chem. Rev. 107 (2007) 381
346
347
348
349
350
351
352
353
354
355
356
Chemical arrangements of penicillin
undertaken in this work. Six thiazolidine amides were synthesized
through N4-C7 -lactam ring opening of penicillin V methyl ester
with various aliphatic, aromatic, and heterocyclic primary amines.
Five 8-hydroxypenillic acid derivatives with side chains of methyl,
propyl, benzyl, diethylaminoethyl, and 2-(bromomethyl)ben-
b-lactam ring were
4437–4492.
382
[12] B. Alcaide, P. Almendros, G. Cabrero, M.P. Ruiz, Stereoselective cyanation of 383
b
4-formyl and 4-imino-b-lactams: application to the synthesis of polyfunctiona- 384
lized g-lactams, Tetrahedron 68 (2012) 10761–10768.
385
[13] B. Alcaide, P. Almendros, A. Luna, et al., Controlled rearrangement of lactam- 386
tethered allenols with brominating reagents: a combined experimental and 387
theoretical study on alpha-versus b-keto lactam formation, Chem. Eur. J. 17 388
zo[d]thiazole groups were yielded via
b-lactam ring rearrange-
(2011) 11559–11566.
389
[14] S. Dekeukeleire, M. D’hooghe, N. De Kimpe, Diastereoselective synthesis of 390
ment from 6-aminopenicillanic acid (6-APA). Parallel synthetic
methods were developed for esterification of 8-hydroxypenillic
bicyclic gamma-lactams via ring expansion of monocydic b-lactams, J. Org. Chem. 391
74 (2009) 1644–1649.
392
acid and
b-lactam ring opening of penicillin V methyl ester. The
[15] W. Van Brabandt, N. De Kimpe, Electrophile-induced ring expansions of b-lactams 393
toward g-lactams, J. Org. Chem. 70 (2005) 8717–8722.
[16] A.K. Mukerjee, A.K. Singh, Reactions of natural and synthetic b-lactams, Synthe- 395
sis-Stuttgart 9 (1975) 547–589.
[17] D.A. Johnson, G.A. Hardcastle Jr., Reaction of 6-aminopenicillanic acid with 397
carbon dioxide, J. Am. Chem. Soc. 83 (1961) 3534–3535.
compounds display biological activities.
394
396
398
357
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358
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Please cite this article in press as: C.-J. Liu, et al., Synthesis of new penicillin derivatives as drug-like molecules for biological screening,
Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.09.008