Patent GB-1340208-A (GB)
Title: Process for producing 6-aminopenicillanic acid
IPC: C07D499/00
Filed: 1970-12-23
Abstract: 1340208 Preparing 6-aminopenicillanic acid OSAKA UNIVERSITY PRESIDENT OF 23 Dec 1970 [26 Dec 1969 2 Feb 1970 13 Feb 1970] 61103/70 Heading C2A 6-Amino-pencillanic acid (6-APA) is prepared by the following procedure: (a) reacting a 6-acylaminopenicillanic acid of Formula (I) wherein R<SP>1</SP> is hydrogen or a substituted or unsubstituted alkyl, aryl, alkenyl, aralkyl or aryloxy group, or a salt thereof, in the presence of an acid binding agent, with a compound (III):- R<SP>2</SP>-X in which X is a halogen atom, compound (III) being selected from the following:- (i) a compound of Formula (III-1) wherein R 4  and R 5  are the same or different and each is an optionally substituted alkyl, aryl, aralkyl, alkoxy, alkylthio, aryloxy or aralkyloxy group or a halogen atom, or R 4  and R 5  together with M 1  form a ring, and M 1  is a phosphorus atom; (ii) a compound of Formula (III-2) wherein R 6 , R 7  and R 8  are the same or different and each is a substituted or unsubstituted alkyl, aryl, aralkyl, alkoxy, alkylthio, aryloxy or aralkyloxy group or a halogen atom, and M 2  is a silicon atom, with the proviso that either all of R 6 , R 7  and R 8  are halogen atoms or at least one of R 6 , R 7  and R 8  together with M 2  forms a linkage of formula (iii) a compound of Formula (III-3) wherein R 9  is a halogen atom or a substituted or unsubstituted alkyl, alkoxy, alkylthio, aryl, aralkyl, aryloxy or aralkyloxy group, R 12  is a halogen atom, and R 10  and R 11  are the same or different and each is a halogen atom, or R 10  and R 11  together with the phosphorus atom form a ring or R 10  and R 11  together represent =O or =S; (iv) phosgene COCl 2 ; (b) reacting the product of step (a) with an imino-halide-forming reagent to give the corresponding imino-halide; (c) reacting the imino-halide with a hydroxyl compound of formula: R<SP>3</SP>-OH in which R<SP>3</SP> is a substituted or unsubstituted alkyl, aryl, aralkyl or cycloalkyl group to form the corresponding imino-ether; and (d) hydrolysing the iminoether under acid conditions with water or a hydroxyl group-containing compound to give 6-APA. The preferred starting compound (I) is a biosynthetic penicillin such as penicillin G or V, used as its salt with an amine, alkali metal or alkaline earth metal. The function of reaction step (a) is to protect the 3-carboxyl group by converting it into a mixed acid anhydride with the compound R<SP>2</SP>-X. The preferred compounds (III) are PCl 3 , POCL 3 , PCl 5 , SiCl 4 , COCl 2 , alkoxy- and haloalkoxy- PCl 2 , aryl-PCl 2 , dialkoxy-PCl, alkoxy-carbonyl chlorides, alkoxy-SiCl 3 , dialkoxy-SiCl 2  and trialkoxy- and tri(haloalkoxy)-SiCl. Suitable acid binding agents are N, N-dimethyl-aniline, lutidine, and pyridine. Conventional imino-halide-forming agents are used, such as POCl 3 , PCl 5 , PBr 5 , PBr 4 , COCl 2 , oxalyl choride, and catechyl-phosphorus trichloride. As the compound R<SP>3</SP>-OH in step (c) there may be used an alkyl or aryl alcohol, preferably methanol, ethanol, n-propanol, nbutanol or isoamyl alcohol. The final hydrolysis (d) of the imino-ether is effected with water and an acid, the latter being produced in situ by reaction of the water with excess phosphorus or silicon halides present from the preceding steps (a) and (b). The 6-APA product is isolated by adjusting the final hydrolysis mixture to the iso-electric point of the 6-APA by addition of a base to about pH4, when the 6-APA precipitates.