Diastereoselective synthesis of trans-2-(1-triphenylmethyl-1H-imidazol-4-yl)cyclopropanecarboxylic acids: key intermediates for the preparation of potent and chiral histamine H3 receptor agents

Procedures for the preparation of both enantiomers of trans-2-(1-triphenylmethyl-1H-imidazol-4-yl)-cyclopropanecarboxylic acid are described. The key step in the synthesis is a 3:1 diastereoselective cyclopropanation of (5R)-trans-4-aza-10,10-dimethyl-3-thia-4-(3-(1-triphenylmethyl-1H-imidazol-4-yl)prop-2-enoyl)tricyclo[5.2.1.0<1,5>]decane-3,3-dione using trimethylsulfoxonium ylide. These cyclopropanes are useful for the preparation of H3 receptor agents.