(3S,6S)-及(3S,6R)-3-苄氧甲基-6-甲基-吗啉-2,5-二酮的 制备及其晶体结构

以2-溴丙酸和N-叔丁氧羰基-O-苄基-L-丝氨酸为起始试剂首先制得N-(2-溴丙基)-O-苄基-L-丝氨酸(BPBS), 在N,N-二甲基甲酰胺(DMF)/三乙胺(Et3N)溶剂中80 ℃经9 h后BPBS发生分子内环化反应生成(3S,6S)-3-苄氧甲基-6-甲 基-吗啉-2,5-二酮(3S,6S)-BMMD]及(3S,6R)-BMMD共存体, 产率70%. 将所制得的共存体以乙酸乙酯为重结晶溶剂, 采用微分重结晶法, 经4次“溶解-部分重结晶”操作循环制得两种纯光学构型的(3S,6S)-BMMD和(3S,6R)-BMMD. 将两种光学纯双手性中心的BMMD分别溶于乙酸乙酯, 室温下培养得(3S,6S)-BMMD和(3S,6R)-BMMD的单晶体, 以X射线衍射法测定上述两种BMMD的分子结构.

Synthesis and Crystal Structures of Chiral (3S,6S)- and (3S,6R)- 3-Benzyloxymethyl-6-methyl-morpholine-2,5-dione

N-(2-Bromopropionyl)-O-benzyl-L-serine (BPBS) was prepared using 2-bromopropionic acid and N-Boc-O-Bzl-L-serine as the starting reagents. BPBS underwent the intra-molecular ring-closing reaction in DMF/Et3N solvent at 80 ℃ for 9 h forming a mixture of two non-enantiomers, i.e. (3S,6S)-benzyloxy- methyl-6-methyl-morpholine-2,5-dione (3S,6S)-BMMD] and (3S,6R)-BMMD with a yield of 70%. Two optically pure enantiomers of BMMD, i.e. (3S,6S)-BMMD and (3S,6R)-BMMD were obtained via 4 operation circles of “solution-partial recrystallization” by means of a differential recrystallization method using ethyl acetate as a solvent. The single crystals of the two isomers of BMMD were grown from ethyl acetate at room temperature. The fine molecular structures of the two isomers were determined by X-ray diffraction analysis of the single crystals.