Cephem compound

Abstract

The invention relates to a highly stable antibacterial agent which is crystalline 7.beta.-[2-(5 -amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate hydrochloride (syn-isomer).

Description

This invention relates to a novel cephem compound which is of value as an antibacterial agent and finds application in the medical field.

More particularly, this invention relates to crystalline 7.beta.-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate hydrochloride (syn-isomer) [hereinafter referred to briefly as compound (I)].

The free form of compound (I), namely 7.beta.-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)-acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate (syn-isomer) (hereinafter referred to as known compound (II)] is described, for example, in Example 6 (4) of EP0261615A2 and is known to have high antibacterial activity.

However, further experimental investigation by the inventors of this invention revealed that the known compound (II) described in the said EP0261615A2 is an amorphous product and the said amorphous known compound (II) has disadvantages, for example, it is unstable, bulky and not so pure, and therefore it is not so suitable for use as a drug.

The inventors of this invention attempted to improve this known compound (II) and succeeded in developing compound (I) which does not have disadvantages as mentioned above and is more suitable for use as a drug. This invention is predicated on the above-mentioned successful endeavor.

Compound (I) can be produced by reacting known compound (II) with HCl (for example, hydrochloric acid, etc.).

This reaction can be carried out in the presence of the common solvent, such as water or the like.

The reaction temperature is not particularly critical. Thus, generally the reaction can be carried out under cooling or warming.

The following is the result of a comparative stability test conducted for demonstrating the advantage of compound (I) over known compound (II).

______________________________________Test samples______________________________________Sample 1 Known compound (II) obtained in Example 6 (4) of EP0261615A2Sample A Compound (I) obtained in Example which appears hereinafter______________________________________

TEST METHOD

The stability of each test sample in air-tight containers at 50.degree. C. was evaluated. The potency of each sample was determined by liquid chromatography and the residual percentage of each compound was calculated.

______________________________________ResultsTest Test Initial After Aftersample item value 15 days 30 days______________________________________Sample 1 Potency 100 57.5 46.3 (residual percentage %)Sample A Potency 100 99.4 99.5 (residual percentage %)______________________________________

It is apparent from the above results that Sample A is more stable than Sample 1.

The following example is further illustrative of the invention.

EXAMPLE

A suspension of 7.beta.-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate (syn-isomer) (10 g) in water (10 ml) is adjusted to pH 1.0 with 2N-hydrochloric acid at 20.degree. C. with stirring. The resulting solution is further stirred at the same temperature for 2 hours and the resultant crystals are collected by filtration and dried to give crystals of 7.beta.-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate hydrochloride (syn-isomer) (6.7 g).

IR (Nujol): 3430, 3250, 1780, 1710, 1645, 1580, 1515 cm.sup.-1.

NMR (D.sub.2 O-NaHCO.sub.3, .delta.): 1.53 (6H, s), 3.06 & 3.40 (2H, ABq, J=18 Hz), 3.70-3.96 (2H, m), 4.15-4.46 (2H, m), 5.10 (2H, broad s), 5.23 (1H, d, J=5 Hz), 5.85 (1H, d, J=5 Hz), 5.95 (1H, d, J=5 Hz), 5.95 (1H, d, J=3 Hz), 7.85 (1H, d, J=3 Hz)

mp: 188.degree. C. (dec.)

Claims

1. Crystalline 7.beta.-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(1-carboxy-1-methylethoxyimino)acetamido]-3-[3-amino-2-(2-hydroxyethyl)-1-pyrazolio]methyl-3-cephem-4-carboxylate hydrochloride (syn-isomer).