Asymmetric Synthesis of 3-Hydroxyprolines by Photocyclization of C(1?)-SubstitutedN-(2-Benzoylethyl)glycine Esters
作者:Andr� Steiner、Pablo Wessig、Kurt Polborn
DOI:10.1002/hlca.19960790709
日期:1996.10.30
C(1′)-substituents. Irradiation of ketones 5d and 5f, bearing H-atoms at C(γ) with respect to the keto function, gave cyclobutanols (Scheme 9) in low yields besides the preferred Norrish-type-II cleavage product. Cyclopentanol 25 was a by-product of the photocyclization of 5c as a result of HC(δ) abstraction from the t-Bu group. The structure of products 20, 22, and 24a, b was established by NMR or X-ray analyses.
手性ñ - (2-苯甲酰乙基) - ñ -tosylglycine酯5A-H和α氨基γ酮酯6是从γ-(甲苯磺酰)醇制备7A-H 。化合物的照射5A-C,E,得到顺式-3-羟基脯氨酸酯20-23(方案6),部分地与完整不对称诱导由C(1') -的取代基,而6得到对映体纯的4-羟基-4-苯基-L-脯氨酸酯24的收率好,但是de较低(方案6)。光环化的定义取决于C(1')取代基的性质和/或大小。酮辐照5d在优选的Norrish -II-型裂解产物之外,图5f和5f所示,相对于酮基官能团在C(γ)处带有H-原子的化合物以低收率得到了环丁醇(方案9)。环戊醇25是的photocyclization的副产品5C为从HC(δ)的抽象的结果吨-Bu基。通过NMR或X射线分析确定产物20、22和24a,b的结构。