Diastereoselective phosphonylation of the chiral cyclic imines were obtained from L-pyroglutamic acid in the presence of TiCl₄. A complex between the imine, carbonyl group of the ester, and titanium was took place. Then, selective trans attack by (EtO)₃P moiety from the opposite less hindered face (re) would account for the diastereoselectivity. The first synthesis of (2S,5R)-5-methyl-5-(phosphono)-proline was reported herein.

中文翻译：

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手性环状亚胺的非对映选择性膦酰化合成磷酸脯氨酸衍生物

_{在TiCl 4}存在下，从L-焦谷氨酸获得手性环状亚胺的非对映选择性膦酰化。发生了亚胺、酯的羰基和钛之间的络合物。然后，(EtO) ₃ P 部分从相对的受阻较小的面 ( re ) 的选择性反式攻击将解释非对映选择性。本文报道了(2 S ,5 R )-5-甲基-5-(膦酰基)-脯氨酸的首次合成。