1860
M. A. Ibrahim et al. / Bioorg. Med. Chem. Lett. 24 (2014) 1856–1861
154.4, 151.2, 147.9, 144.7, 139.0, 137.2, 137.0, 128.3, 127.7, 127.8, 127.6, 118.7,
References and notes
111.1, 110.8, 106.7, 106.5, 65.4, 65.1, 50.6, 45.4, 44.6, 42.5, 41.2, 35.9, 30.9,
29.2, 22.6, 8.5, 7.6. HRMS (-ESI-TOF) m/z for
726.2943, found 726.2945.
C
39H42FN5O8 [MꢀH]ꢀ calcd
General procedure for preparation of pipemidic acid bioconjugates 6a–e:
solution of Cbz-amino acid-Bt (1.513 mmol) in tetrahydrofuran (5 mL) was
added to solution of pipemidic acid (1.664 mmol) and triethylamine
A
a
(3.026 mmol) in water (2 mL). The mixture was stirred for 3 h. at room
temperature. The solvent was evaporated under reduced pressure then a
solution of 2 N HCl was added with stirring to the residue to give precipitate
which was filtered, and washed several times with 2 N HCl to give the desired
product.
2-(4-(2-(Benzyloxycarbonylamino)acetyl)piperazin-1-yl)-8-ethyl-5-oxo-5,8-
dihydro pyrido[2,3-d]pyrimidine-6-carboxylic acid (Cbz-Gly-Pip-OH, 6a):
White microcrystals (82%); mp >300 °C; 1H NMR (DMSO-d6) d 9.23 (s,
1H), 8.98 (s, 1H), 7.37–7.30 (m, 6H), 5.04 (s, 2H), 4.44–4.37 (m, 2H), 4.02–
3.89 (m, 6H), 3.64–3.59 (m, 4H), 1.37 (t, J = 7 Hz, 3H); 13C NMR (DMSO-d6)
d 177.1, 167.5, 165.2, 160.7, 160.2, 156.5, 155.1, 150.8, 137.1, 128.3, 127.8,
127.7, 109.6, 108.7, 65.4, 45.9, 43.8, 43.5, 42.1, 14.4. HRMS (+ESI-TOF) m/z
for C24H26N6O6 [M+H]+ calcd 495.1987, found 495.1989.
2-(4-(2-(Benzyloxycarbonylamino)propanoyl)piperazin-1-yl)-8-ethyl-5-oxo-
5,8-dihydro pyrido[2,3-d]pyrimidine-6-carboxylic acid (Cbz-L-Ala-Pip-OH,
6b): White microcrystals (51%); mp >300 °C; 1H NMR (CDCl3) d 9.33 (s,
1H), 8.71 (s, 1H), 7.36–7.30 (m, 5H), 5.91–5.89 (m, 1H), 5.11 (s, 2H), 4.77
(t, J = 7.5 Hz, 1H), 4.42–3.60 (m, 10H), 1.52–1.46 (m, 4H), 1.39 (d,
J = 6.8 Hz, 2H); 13C NMR (CDCl3)d 177.8, 175.9, 171.7, 166.5, 161.1,
155.9, 149.4, 136.4, 128.7, 128.1, 126.5, 115.1, 111.3, 109.9, 67.2, 49.6,
46.9, 46.7, 44.3, 44.0, 19.4, 18.7, 14.9. HRMS (-ESI-TOF) m/z for C25H28N6O6
[MꢀH]ꢀ calcd 507.1991, found 507.1998.
13. Sanchez, J. P. Eur. Pat. Appl. EP 304087 A2 19890222, 1989.
14. JP Pat., 56 053 679 A 19810513, 1981.
16. Pongracz, K.; Frank, J.; Kulcsar, G.; Medzihradszky, K.; Nadasi, L.; HU 36483 A2
19850930, 1985.
17. Pongracz, K.; Frank, J.; Kulcsar, G.; Medzihradszky, K.; Nadasdi, L.; Szokan, G.
HU 36842 A2 19851028, 1985.
20. de Souza Ferreira, S. B.; de Assis Dias, B. R.; Obregón, C. S.; Gomes, C. C.; de
Araújo Pereira, R. R.; Ribeiro Godoy, J. S.; Estivalet Svidzinski, T. I.; Bruschi, M. L.
26. Experimental section: Melting points were determined on a capillary point
apparatus equipped with a digital thermometer. NMR spectra were recorded in
CDCl3 or DMSO-d6 on Mercury NMR spectrometers operating at 300 MHz for
1H (with TMS as an internal standard) and 75 MHz for 13C. Microwave assisted
2-(4-(2-(Benzyloxycarbonylamino)-3-methylbutanoyl)piperazin-1-yl)-8-ethyl-5-
oxo-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylic acid (Cbz-L-Val-Pip-OH,
6c): White microcrystals (68%); mp >300 °C; 1H NMR (CDCl3) d 9.32 (s, 1H),
8.66 (s, 1H), 7.34–7.31 (m, 5H), 5.55 (d, J = 9 Hz, 1H), 5.08 (s, 2H), 4.56–4.50
(m, 1H), 4.32 (q, J = 7.2 Hz, 2H), 4.18–3.59 (m, 8H), 2.03–1.94 (m, 1H), 1.48 (t,
J = 7.2 Hz, 3H), 0.99 (d, J = 6.7 Hz, 3H), 0.92 (d, J = 6.7 Hz, 3H). HRMS (+ESI-TOF)
m/z for C27H32N6O6 [M+H]+ calcd 537.2451, found 537.2452.
2-(4-(2-(Benzyloxycarbonylamino)-3-phenylpropanoyl)piperazin-1-yl)-8-ethyl-
5-oxo-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylic acid (Cbz-L-Phe-Pip-OH,
6d): White microcrystals (64%); mp >300 °C; 1H NMR (DMSO-d6) d 9.23 (s,
1H), 8.99 (s, 1H), 7.33–7.19 (m, 10H), 4.96 (s, 2H), 4.75–4.67 (m, 1H), 4.40 (q,
J = 6.4 Hz, 2H), 4.15–3.56 (m, 5H), 3.22–2.80 (m, 5H), 1.36 (t, J = 7.3 Hz, 3H).
HRMS (+ESI-TOF) m/z for C31H32N6O6 [M+H]+ calcd 585.2434, found 585.2436.
(S)-2-(4-(3,11-Dioxo-1,13-diphenyl-2,12-dioxa-4,10-diazatridecanecarbonyl)-
piperazin-1-yl)-8-ethyl-5-oxo-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylic
acid (Cbz-L-Lys(Cbz)-Pip-OH, 6e): White microcrystals (80%); mp 140–142 °C;
1H NMR (DMSO-d6) d 10.19 (br s, 1H), 9.21 (s, 1H), 8.97 (s, 1H), 7.58–7.52 (m,
1H), 7.38–7.28 (m, 11H), 5.02 (s, 2H), 4.98 (s, 2H), 4.48–4.36 (m, 2H), 4.05–
3.88 (m, 3H), 3.72–3.54 (m, 3H), 3.09–2.97 (m, 5H), 1.61–1.53 (m, 1H), 1.36 (t,
J = 6.9 Hz, 4H), 1.19 (t, J = 7.3 Hz, 4H); 13C NMR (DMSO-d6) d 177.1, 170.6,
165.2, 160.6, 160.2, 156.1, 155.9, 155.0, 150.7, 137.2, 137.0, 128.3, 127.8,
127.7, 127.7, 127.6, 109.6, 108.7, 65.4, 65.1, 50.7, 45.9, 45.4, 44.0, 43.6, 30.9,
reaction was carried out with
a single mode cavity Discover Microwave
Synthesizer (CEM Corporation, NC). The reaction mixtures were transferred
into a 10 mL glass pressure microwave tube equipped with a magnetic stir bar.
The tube was closed with a silicon septum and the reaction mixture was
subjected to microwave irradiation (Discover mode; run time: 60 s;
PowerMax-cooling mode. Mass spectrometry was done with 6220 Agilent
(Santa Clara, CA) TOF in electrospray ionization (ESI) mode with positive and
negative ESI-MS method in both Profile and Centroid mode.
General procedure for preparation of ciprofloxacin bioconjugates. 4a–c. A solution
of Cbz-amino acid-Bt (1.386 mmol) in tetrahydrofuran (5 mL) was added to a
suspension of ciprofoloxacin (1.524 mmol) and triethylamine (3.048 mmol) in
water (2 mL). The mixture was stirred for 3 h. at room temperature. The
solvent was evaporated under reduced pressure then a solution of 2 N HCl was
added to the residue and stirred for 15 min. to give precipitate which was
filtered then washed several times with 2 N HCl to give the desired product.
7-(4-(2-(Benzyloxycarbonylamino)acetyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-
4-oxo-1,4-dihydroquinoline-3-carboxylic acid (Cbz-Gly-Cip-OH, 4a): White
microcrystals (68%); mp 150–152 °C; 1H NMR (CDCl3) d 8.63 (s, 1H), 7.86 (d,
J = 12.7 Hz, 1H), 7.36–7.29 (m, 6H), 5.89 (s, 1H), 5.13 (s, 2H), 4.13–4.09 (m, 2H),
3.91–3.85 (m, 2H), 3.71–3.53 (m, 3H), 3.44–3.28 (m, 3H), 1.41–1.21 (m, 5H);
13C NMR (CDCl3) d 176.8, 166.8, 166.7, 156.3, 151.8, 147.5, 145.2, 138.9, 136.4,
128.6, 128.2, 128.0, 112.4, 107.9, 105.4, 67.0, 49.7, 49.4, 44.3, 42.7, 41.7, 35.5,
8.4; Anal. calcd for C27H27FN4O6ꢃ1/3H2O: C, 61.36; H, 5.28; N, 10.60; found: C,
61.46; H, 4.98; N, 10.59.
29.2, 22.6, 14.4, 8.5. HRMS (+ESI-TOF) m/z for
C
36H41N7O8 [M+H]+ calcd
700.3083, found 700.3087.
General procedure for preparation of norfloxacin bioconjugates 8a–c: A solution
of Cbz-amino acid-Bt (0.999 mmol) in tetrahydrofuran (5 mL) was added to a
suspension of norfoloxacin (1.099 mmol) and triethylamine (1.998 mmol) in
water (2 mL). The mixture was stirred for 3 h. at room temperature. The
solvent was evaporated under reduced pressure and a solution of 2 N HCl was
added to the residue and stirred for 15 min. to give precipitate which filtered
then washed several times with 2 N HCl to give the desired product.
7-(4-(2-(Benzyloxycarbonylamino)acetyl)piperazin-1-yl)-1-ethyl-6-fluoro-4-
oxo-1,4-dihydroquinoline-3-carboxylic acid (Cbz-Gly-Nor-OH, 8a): White
microcrystals (82%); mp 214–216 °C; 1H NMR (DMSO-d6) d 8.92 (s, 1H), 7.87
(d, J = 13.2 Hz, 1H), 7.37–7.31 (m, 6H), 7.16 (d, J = 7.3 Hz, 1H), 5.04 (s, 2H), 4.57
(q, J = 7.1 Hz, 2H), 3.96 (d, J = 5.9 Hz, 2H), 3.69–3.63 (m, 4H), 3.35–3.29 (m,
4H), 1.41 (t, J = 7.1 Hz, 3H); 13C NMR (DMSO-d6) d 176.1, 167.4, 166.1, 156.5,
154.4, 151.1, 148.5, 145.1, 137.1, 128.3, 127.7, 119.4, 111.3, 111.0, 107.1,
106.1, 65.4, 49.5, 49.2, 49.1, 43.6, 42.0, 41.1, 14.4. Anal. calcd for
C
26H27FN4O6ꢃH2O: C, 59.08; H, 5.53; N, 10.60; found: C, 59.10; H, 5.25; N,
10.91.
(S)-7-(4-(2-(Benzyloxycarbonylamino)propanoyl)piperazin-1-yl)-1-ethyl-6-
fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (Cbz-L-Ala-Nor-OH, 8b):
White microcrystals (79%); mp 192–194 °C; 1H NMR (DMSO-d6) d 8.94 (s,
1H), 7.90 (d, J = J = 12.9 Hz, 1H), 7.34–7.18 (m, 6H), 5.01 (s, 2H), 4.62–4.55 (m,
3H), 3.72–3.61 (m, 4H), 3.34–3.25 (m, 4H), 1.40 (t, J = 7 Hz, 3H), 1.21 (d,
J = 6.9 Hz, 3H); 13C NMR (DMSO-d6) d 176.0, 170.6, 166.0, 155.5, 154.4, 151.1,
148.4, 145.0, 137.0, 128.2, 127.6, 125.3, 119.5, 114.8, 111.3, 107.1, 106.1, 65.3,
49.7, 49.3, 49.1, 44.4, 41.3, 17.6, 14.4. Anal. calcd for C27H29FN4O6ꢃH2O: C,
59.77; H, 5.76; N, 10.33; found: C, 60.07; H, 5.54; N, 10.16.
7-(4-(2-(Benzyloxycarbonylamino)propanoyl)piperazin-1-yl)-1-ethyl-6-fluoro-4-
oxo-1,4-dihydroquinoline-3-carboxylic acid (Cbz-DL-Ala-Nor-OH, 8b+8b0):
White microcrystals (75%); mp 210–212 °C; 1H NMR (CDCl3) d 8.65 (s, 1H),
8.02 (d, J = 12.6 Hz, 1H), 7.37–7.24 (m, 5H), 6.85–6.82 (m, 1H), 5.82 (d,
J = 7.5 Hz, 1H), 5.08 (s, 2H), 4.75–4.68 (m, 2H), 4.75–4.68 (m, 1H), 4.41–4.26
(m, 2H), 4.08–3.10 (m, 8H), 1.73–1.56 (m, 3H), 1.45–1.32 (m, 3H); 13C NMR
(CDCl3) d 177.1, 175.1, 171.4, 167.4, 155.9, 147.6, 145.7, 145.6, 137.2, 136.5,
7-(4-(2-(Benzyloxycarbonylamino)propanoyl)piperazin-1-yl)-1-cyclopropyl-6-
fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (Cbz-L-Ala-Cip-OH, 4b):
White microcrystals (72%); mp 128–130 °C; 1H NMR (CDCl3) d 8.70 (s, 1H),
7.96 (d, J = 12.9 Hz, 1H), 7.35–7.27 (m, 6H), 5.82 (d, J = 7.7 Hz, 1H), 5.11 (s, 2H),
4.74 (t, J = 7.2 Hz, 1H), 4.04–3.70 (m, 4H), 3.44–3.27 (m, 4H), 1.48–1.21 (m,
8H); 13C NMR (CDCl3) d 177.1, 171.2, 155.8, 152.1, 147.7, 145.5, 141.9, 139.1,
136.5, 128.7, 128.3, 128.1, 112.8, 112.5, 108.3, 105.4, 67.0, 50.2, 49.7, 49.6,
46.8, 45.4, 42.0, 35.5, 19.4, 8.4; HRMS (-ESI-TOF) m/z for C28H29FN4O6 [MꢀH]ꢀ
calcd 535.1998, found 535.2001.
(S)-1-Cyclopropyl-7-(4-(3,11-dioxo-1,13-diphenyl-2,12-dioxa-4,10-diazatridecan-
ecarbonyl)piperazin-1-yl)-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(Cbz-L-Lys(Cbz)-Cip-OH, 4c): White microcrystals (77%); mp 135–137 °C; 1H
NMR (DMSO-d6) d 8.66 (s, 1H), 7.93 (d, J = 13.2 Hz, 1H), 7.62–7.53 (m, 2H),
7.35–7.25 (m, 11H), 5.02 (s, 2H), 4.98 (s, 2H), 4.47–4.43 (m, 1H), 3.81–3.72 (m,
4H), 3.58–3.54 (m, 2H), 3.09–2.95 (m, 4H), 1.62–1.51 (m, 2H), 1.40–1.29 (m,
6H), 1.21–1.16 (m, 4H); 13C NMR (DMSO-d6)d 176.2, 170.3, 165.8, 156.1, 155.9,