作者:Thomas L. Gilchrist、Américo Lemos、Carol J. Ottaway
DOI:10.1039/a703170j
日期:——
The azabicyclo[3.2.0]heptan-7-ones 4, 10, 16 and 24 have been prepared from pyrrole. The same general approach has been used for all these derivatives; namely, substitution of pyrrole at the 2- and 5-carbon atoms, catalytic hydrogenation to produce pyrrolidine-2-acetic acid derivatives, and cyclisation using tris(1,3-dihydro-2-oxobenzoxazol-3-yl)phosphine oxide 6. The catalytic hydrogenation of 2,5-disubstituted pyrroles gives only the corresponding cis-2,5-disubstituted pyrrolidines. The hydrogenation proceeds more easily when the nitrogen atom bears a tert-butoxycarbonyl substituent. The N-tert-butoxycarbonylpyrroles 8 and 21 bearing an α-substituent in the acetate side chain were hydrogenated with a high degree of facial stereoselectivity. This allowed the 6-phthalimidoazabicyclo[3.2.0]heptan-7-one 24 to be isolated as a single diastereoisomer. The X-ray crystal structure of a precursor, the triester, 22a, has been obtained.
由吡咯制备出氮杂双环[3.2.0]庚烷-7-酮 4、10、16 和 24。所有这些衍生物都采用了相同的一般方法,即在 2 碳原子和 5 碳原子上取代吡咯,催化加氢生成吡咯烷-2-乙酸衍生物,并使用三(1,3-二氢-2-氧代苯并恶唑-3-基)氧化膦 6 进行环化。2,5-二取代吡咯的催化氢化反应只能得到相应的顺式-2,5-二取代吡咯烷。当氮原子带有叔丁氧羰基取代基时,氢化反应更容易进行。醋酸侧链上带有 α 取代基的 N-叔丁氧羰基吡咯 8 和 21 在氢化过程中具有很高的面立体选择性。这使得 6-邻苯二甲酰亚胺基氮杂双环[3.2.0]庚烷-7-酮 24 以单一非对映异构体的形式分离出来。前体三酯 22a 的 X 射线晶体结构已经获得。