AN EFFICIENT SYNTHESIS OF N,N'-LINKED OLIGOUREAS

This paper reports an efficient synthesis of N-alkyl-N,N'-linked oligo ureas [-NR-CO-NH-CH2CH2-](n), which involves the repetition of three s teps: (1) main-chain extension by ring-opening of N-(2-nitrobenzenesul fonyl)-2-imidazolidone (1) by a secondary amine RR'NH to afford sulfon amide RR'N-CO-NH-CH2CH2-NH-SO2Ar (2) side-chain attachment by N-alkyla tion of the sulfonamide with alkyl halide R''X, and (3) removal of the sulfonyl group to give a new secondary amine RR'N-CO-NH-CH2CH2-NHR''. A tetraurea was prepared in 10 steps and 58% overall yield by this me thod. (C) 1998 Elsevier Science Ltd. All rights reserved.