The addition of lithiated [1-(p-toluenesulfonyl)alk-2-enyl] carbamates to α-stereogenic aldehydes proceeds with steric approach control according to the Felkin-Anh model to produce α‘-carbamoyloxy-α,β-enones by carbonyl migration and elimination of p-toluenesulfinate. Conversion of two enones to 1,3-dioxan-2-one 9 and to (2S,3S,4S,5S)-methyl-5-(dibenzylamino)-4-(N,N-diisopropylcarbamoyloxy)-3-hydroxy-2-isopropyl-7-methyloctanoate (16a), respectively, furnished samples suitable for X-ray crystal structure analyses to confirm the stereochemical course of the addition step.
将
锂化的[1-(对
甲苯磺酰基)
烯-2-
烯基]
氨基甲酸酯与α-立体异构体醛的反应按照Felkin-Anh模型进行,采用立体接近控制,生成α‘-
氨基羟基-α,β-
烯酮,通过羰基迁移和对
甲苯磺酸酯的消除反应。将两个
烯酮分别转化为1,3-二
氧六烷-2-
酮9和(2S,3S,4S,5S)-
甲基-5-(二
苄基氨基)-4-(
N,N-二异丙基氨基羟基)-3-羟基-2-
异丙基-
7-甲基辛酸酯(16a),获得适合X射线晶体结构分析的样品,以确认加成步骤的立体
化学过程。