Janssen Pharmaceutica Nv

Herman Van Belle

Theo Frans Meert

Willy Joannes Van Laerhoven

Method of treating pain with draflazine-analogues

There is disclosed a process for preparing (l)-(-)-2-aminocarbonyl)-N-(4-amino-2,6-dichlorophenyl)-4-�5,5-bis(4-fluor ophenyl)pentyl!-1-piperazineacetamide which comprises the steps of (a) cyclizing (-)-(S,S)-N.sup.1,N.sup.2 -bis(1-phenylethyl)-1,2-ethanediamine with 2,3-dibromopropanamide in a reaction-inert solvent in the presence of a base, thus yielding an intermediate; (b) resolving the intermediate of into two stereoisomers and recovering thereby �1(S),2A,4(S)!-1,4-bis(1-phenylethyl)-2-piperazinecarboxamide; (c) hydrogenolyzing �1(S),2A,4(S)!-1,4-bis(1-phenylethyl)-2-piperazinecarboxamide under a hydrogen atmosphere in an alkanol in the presence of a hydrogenation catalyst to produce (+) -2-piperazinecarboxamide; (d) reductively N-alkylating (+)-2-piperazinecarboxamide with 5,5-bis(4-fluorophenyl)pentaldehyde under a hydrogen atmosphere in an alkanol in the presence of a hydrogenation catalyst to produce a compound of the formula: ##STR1## (e) N-alkylating the compound of Formula (VII) with an alkylating reagent of the formula: ##STR2## wherein W represents a reactive leaving group, in a reaction-inert solvent in the presence of a base to form the nitro analog of the desired compound; and (f) reducing the nitro compound in the presence of a reducing agent in a reaction-inert solvent.

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Vosselaar, Belgium

Herman Van Belle