Stereoselective Synthesis of (7aS)-1-Methylenehexahydro-1H-pyrrolizine and (−)-Heliotridane from N-Diphenylmethyl-(S)-proline Ethyl Ester
作者:I. L. Lysenko、O. G. Kulinkovich
DOI:10.1007/s11178-005-0123-0
日期:2005.1
Alkaloid (7aS)-1-methylenehexahydro-1H-pyrrolizine was synthesized from N-diphenylmethyl-(S)-proline ethyl ester by cyclopropanation of the ester group with ethylmagnesium bromide in the presence of titanium tetraisopropoxide, replacement of the protecting group on the nitrogen atom, and cationic cyclopropylallyl isomerization of (S)-1-(1-ethoxycarbonylpyrrolidin-2-yl)cyclopropyl sulfonate into the corresponding allyl bromide. Stereoselective reduction of (7aS)-1-methylenehexahydro-1H-pyrrolizine with sodium tetrahydridoborate in the presence of nickel chloride afforded (−)-heliotridane [(1S,7aS]-1-methylhexahydro-1H-pyrrolizine] in high yield.
Synthesis of the alkaloids (−)-heliotridane and (−)-isoretronecanol via π-allyltricarbonyliron lactam complexes.
作者:Julian G. Knight、Steven V. Ley
DOI:10.1016/0040-4039(91)85056-b
日期:1991.11
A novel synthesis of the pyrrolizidine alkaloids (−)-heliotridane (1) and (−)-isoretronecanol (2) is described. The key steps involve the conversion of a proline-derived carbamate (10) into the π-allyltricarbonyliron lactam complex (4) and the exhaustive carbonylation of this to give the pivotal intermediate γ-lactam (3). Lactam (3) has been converted into the title compounds by standard methods.