Natural cinchonidine, functions

In 2006, Ohkata and coworkers found that the natural cinchonidine (CD) functions as a Brans ted base catalyst (1 mol%) in the reaction between chloromethyl ketones 193 and (3-substituted methylidenemalononitriles 194 to furnish the corresponding tetrasubstituted trans-cyclopropanes 195 with enantioselectivities of up to 82% ee (Scheme 9.68) [62]. The 9-0H-protected derivatives provided almost no enantios-electivity, indicating that the hydrogen bonding is crucial for stereoinduction. 

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