Stage II. Process Development Laying the Foundation

Process development work at Ranbaxy began with the aim to develop a simple, practical, and efficient method for the preparation of crystalline imipenem monohydrate, which is thermally stable, has a uniform degree of crystallinity, and is of high purity. After extensive experimentation, a process was developed for the isolation of pure crystalline imipenem monohydrate from a solution containing imipenem. The process does not use capital-intensive techniques of lyophilization or freeze crystallization nor the time-consuming purification process of column chromatography using expensive hydro-phobic resins. 

Case Study 5 illustrates another case where several seemingly acceptable processes 

Structurally, isotretinoin is a highly conjugated molecule consisting of a substituted cyclohexene moiety and a nine-carbon polyene side chain with a terminal carboxy group. All but one of the double bonds (the Cl3 double bond) in the side chain are trans, and it is the stereospecific construction of this polyene side chain that has challenged synthetic organic chemists for the past almost three decades. Commercially and readily available P-ionone has been used conveniently for the construction of the cyclohexene part of isotretinoin. Several approaches were available in the literature for the synthesis of isotretinoin. They all suffered from one or another drawback that made them commercially unworkable. 

Another process describes a process involving use of a phosphonate ester (as a C 

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