Cilexetil synthesis

The synthesis of candesartan cilexetil (4) by Takeda Chemical Industries is illustrated in Scheme 9.7. Cyclization of methyl 2,3-diaminobenzoate (29) with tetraethoxymethane... 

The different stereoselective routes explored toward the synthesis of the tricyclic p-lactam sanfetrinem cilexetil (GV 118819) [45] perfectly illustrate advantages and drawbacks of the approach to enantiomerically pure drugs based on the use of commercially available chiral non-racemic substrates. 

A recent patent for candesartan cilexetil describes the formation of the benzimidazole at a relatively late stage of the synthesis by cyclization of the highly functionalized diaminobenzene core under modified Phillips conditions with tetraethyl orthocarbonate at 90 Alternative syntheses of candesartan cilexetil use similar condensation conditions on variously elaborated benzimidazole precursors. ... 

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