Phosphorus chloride amide cleavage with

The first effective method of side chain cleavage made use of the reaction of (179) with nitrosyl chloride (152). Loss of nitrogen from the intermediate diazo compound (181) gives imine (182) which on hydrolysis provides 7-ACA (180) and the lactone (183). This provided a route to substantial quantities of (180) thus allowing the preparation of many side chain derivatives. Later a more efficient procedure made use of phosphorus pentachloride followed by cleavage of an imino ether (153). The utility of other phosphorus halogen compounds for cleavage of the amide bond has also been described (154). 

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