1
212
K. Y. Chang et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1211±1214
give corresponding 5-amino pyrazole derivatives (9a±c)
in good yield. The quaternary cephalosporin derivatives
were prepared as follow: 7-[2-(2-Aminothiazol-4-yl)-2-(Z)-
methoxyiminoacetamido]cephalosporanic acid (456 mg, 1
mmol) was suspended in methylene chloride (10 mL)
under nitrogen atmosphere. N-methyl-N-(trimethylsilyl)-
tri¯uoroacetamide (0.7 mL, 3.8 mmol) was added, and the
mixture was stirred for 1 h. Trimethylsilyl iodide (0.4 mL,
column with a mixture of acetonitrile and water (6:1,
v/v). Lyophilization of collected solution gave 7-[(Z)-2-
(2-amino-1,3-thiazol-4-yl)-2-(methoxyimino)acetamido]-
3-[(3-(5-amino-1-methylpyrazol-3-yl)pyridinium)methyl]
ceph-3-em-4-carboxylate (1j) as an amorphous colorless
ꢀ
1
solid in 42% yield: mp 220±221 C (dec); H NMR
(DMSO-d , 300 MHz) d 3.07, 3.52 (2H, ABq, J=17.5 Hz,
6
C ±H), 3.62 (3H, s, OCH ), 3.77 (3H, s, pyrazole-NCH ),
5.05 (1H, d, J=4.9 Hz, C ±H), 5.09, 5.73 (2H, ABq,
4
3
3
2.8 mmol) was added to the resulted pale yellow solu-
6
tion, and the solution was stirred for additional 30 min.
The solvent was evaporated in vacuo to aord the 3-
iodomethyl cephem as a viscous yellowish residue. The
residue was dissolved in acetonitrile (4 mL) and tetra-
hydrofuran (0.37 mL), which make a role to destroy
excess of trimethylsilyl iodide, was added. 3-(Pyridine-3-
yl)-5-amino-1-methylpyrazole (9b) (175 mg, 1 mmol)
dissolved in acetonitrile (4 mL) was added to the solu-
tion. The reaction mixture was stirred at room tempera-
ture for 16 h, followed by addition of 5% methanolic
acetone (20 mL) to precipitate iodide salt of 1j. The crude
iodide salt was dissolved in water (1 mL) and neutralized
with powder sodium bicarbonate (52 mg). The resulting
solution was directly chromatographed on silica gel
J=17.5 Hz, C ±CH -), 5.62 (1H, d, J=4.9 Hz, C ±H), 5.63
3
(2H, brs, pyrazole-NH ), 5.95 (1H, s, pyrazole-H), 6.69
2
(1H, s, thiazole-H), 7.20 (2H, brs, thiazole-NH ), 8.08 (1H,
2
2
7
dd, J=6.01 Hz, J=8.13 Hz, pyridine-H), 8.72 (1H, d,
J=8.13 Hz, pyridine-H), 9.36 (1H, d, J=6.01 Hz, pyri-
dine-H), 9.53 (1H, d, J=8.12 Hz, pyridine-H), 9.82 (1H,
brs,-CONH-); anal. calcd for C H N O S : C, 48.50; H,
23
23
9 5 2
4.07; N, 22.13. Found C, 48.73; H, 3.95; N, 21.91. Cepha-
losporins prepared as described above are shown in
Scheme 2.
The in vitro activity of the compounds (1a±k) against
Gram-positive and Gram-negative bacteria were deter-
mined by an agar dilution method and was summarized
in Table 1. The MIC values for cefpirome against the
same strains are shown for comparison. In Table 1,
almost all the cephalosporins showed well-balanced
antibacterial activity against Gram-positive and Gram-
negative bacteria except for Enterobacter cloacae P99.
As indicated by comparison of MICs of 1c±e and 1f±h,
the overall activity of 1c±e, 1f-h and 1i±k has a tendency
to diminish in 2- to 4-fold with increasing chain length
at the C-2 position of pyrazole ring. Replacement of
hydrogen (1a) with hydroxymethyl (1c), carbamoyl (1f),
and amino (1i) at the C-5 position of pyrazole ring
beared fruitful in improving the activity in 2- to 6-fold.
Among new series, 1i has the best activity against
Gram-positive and Gram-negative bacteria including P.
Figure 1.
ꢀ
ꢀ
Scheme 1. Reagents and conditions: (a) DMA acetal or DMF acetal, 110 C, 5 h, 98%; (b) NH NH
2
2
H
2
O, EtOH, 80 C, 4 h, 98%; (c) (CO Et)
2
2
, EtONa,
ꢀ
ꢀ
7
8 C, 13 h, 84%; (d) NH
0%); (g) CH
2
NHR , AcOH, 105 C, 7 h, (6a, 83%; 6b, 61%; 6c, 63%); (e) NH
2
CN, 55%, NaH, t-BuOH, abs-ether, 40 C, 24 h, 65%; (h) NH
4
OH, rt, 35 h, 95%; (f) LAH, THF, rt, 5 h, (8a, 95%; 8b, 8c,
ꢀ
ꢀ
9
3
2
NHR , 2N-HCl, IPA, 80 C, 4 h, (9a, 74%; 9b, 57%; 9c, 30%).
2