Torcan Chemical Ltd

Yee-Fung Lu

Jan Oudenes

Raymond So

Clarke Slemon

Teng-Ko Ngooi

Casimir G Antczak

Yong Tao

James L Tindall

Dan To

Sildenafil, a known pharmaceutical chemical useful in treatment of male sexual dysfunction, is prepared by processes in which the final chemical intermediate is of significantly lower basicity than sildenafil itself, so that sildenafil can be extracted in substantially pure form from the organic reaction mixture in which it is made by adding an aqueous medium of appropriately chosen acidic pH and causing phase shift of the sildenafil to occur selectively into the aqueous phase.

Processes for preparing sildenafil

Nizatidine is prepared by reacting N-[2-[[[2-(hydroxymethyl)-4-thiazolyl]methyl]thio]ethyl]-N'-methyl-2-nitro -1,1-ethenediamine, with an aryl- or tert.alkyl-sulfonyl halide in the presence of a tertiary amine base and a sulfonation catalyst to form the corresponding sulfonate ester, reacting the sulfonate ester so formed with an excess of dimethylamine, and recovering the nizatidine so formed.

Nizatidine preparation

Cisapride, i.e. cis-4-amino-5-chloro-N-�1-�3-(4 fluoro-phenoxy)propyl!-3-methoxy-4-piperidinyl!-2-methoxy-benzamide, and similar benzamide derivatives, are prepared from novel 1-aryloxyalkyl- or 1-aralkyl-3-arylcarbonyloxy-4-oxo-piperidines, by nuclear substituent re arrangement involving acyl transfer under animal forming conditions, to give the corresponding 1-aryloxyalkyl- or 1-aralkyl-3-hydroxy-4-lower alkoxy-4-arylamido piperidine. This in turn is readily converted to the corresponding 3-oxo-4-arylamido-piperidine by reaction with strong organic acid, which can then be reduced, deprotected and 3-methylated to give the final compound, e.g. cisapride.

Preparation of cisapride

In a process for making synthetic prostaglandin-type compounds such as misoprostol, organo metallic cuprate complexes capable of reacting with cyclopentenones are prepared by reaction of an alkyl lithium compound with a cuprous halide, followed by reaction of the resulting complex with a vinyl stannane, using an excess of alkyl lithium in the initial reaction and maintaining the excess present during the formation of the organo metallic cuprate complex.

Misoprostol

Cisapride, i.e. cis-4-amino-5-chloro-N-[1-[3-(4 fluoro-phenoxy)propyl]-3-methoxy-4-piperidinyl]-2-methoxy-benzamide, and similar benzamide derivatives, are prepared from novel 1-aryloxyalkyl- or 1-aralkyl-3-arylcarbonyloxy-4-oxo-piperidines, by nuclear substituent re arrangement involving acyl transfer under animal forming conditions, to give the corresponding 1-aryloxyalkyl- or 1-aralkyl-3-hydroxy-4-lower alkoxy-4-arylamido piperidine. This in turn is readily converted to the corresponding 3-oxo-4-arylamido-piperidine by reaction with strong organic acid, which can then be reduced, deprotected and 3-methylated to give the final compound, e.g. cisapride.

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Scarborough, Canada

Yee-Fung Lu