| 摘要 |
PURPOSE:To simply obtain the subject compounds which are beta-amino acids such as bestatin in a high yield by using a novel alpha-substituted carboxylic ester derivative as the raw material and reacting the compound with a specified imine in the presence of a boron triflate and a base. CONSTITUTION:A novel alpha-substituted carboxylic acid ester derivative of formula I [R<1> is protecting group of group having general formula -XH; R<2> is H or lower alkyl (which may be substituted by cycloalkyl, aryl, heterocyclic group, group having general formula -XH; R<3> is protecting group of carboxylic group; X is O, S, selenium, sulfoxide, sulfone or selenoxide] is reacted with an imine of formula II [R<4> is R<2>; R<5> is H or R<2>; R<6> is protecting group of amino] such as N-benzyl-benzylimine in the presence of a boron triflate of formula III (R<7> and R<8>=R<2>) such as di-n-butylboryl triflate and a base such as diisopropylethylamine, preferably in a solvent and stream of nitrogen, thus obtaining the objective compound of formula IV. |
