In the work reported herein, the concise and enantioselective total synthesis of the Schizozygine alkaloid (−)-strempeliopine was developed. This synthetic strategy featured the palladium-catalyzed decarboxylative asymmetric allylic alkylation of N-benzoyl lactam to set up the absolute configuration at the C20 position, a highly diastereoselective one-pot Bischler–Napieralski/lactamization and iminium
Application of Cross-Conjugated Heteroaromatic Betaines to the Synthesis of the Schizozygane Alkaloid (±)-Strempeliopine
作者:Drew R. Bobeck、Hyoung Ik Lee、Andrew C. Flick、Albert Padwa
DOI:10.1021/jo901336z
日期:2009.10.2
An efficient stereocontrolled route to the isoschizozygane alkaloid core has been developed utilizing an intramolecular1,4-dipolarcycloaddition of a cross-conjugated heteroaromaticbetaine. The resulting cycloadduct undergoes loss of COS, and further reduction delivers a 5a-azaacenaphthylene intermediate that was transformed into the isoschizozygane skeleton upon treatment with acid. A variation
A totalsynthesis of (−)-strempeliopine is disclosed that enlists a powerful SmI2-mediated and BF3·OEt2-initiated dearomative transannular radical cyclization onto an indole by an N-acyl α-aminoalkyl radical that is derived by single electron reduction of an in situ generated iminium ion for formation of a quaternary center and the strategic C19–C2 bond in its core structure.
Stereospecific total synthesis of (±)-strempeliopine
作者:Josef Hájíček、Jan Trojánek
DOI:10.1016/s0040-4039(01)81789-5
日期:1981.1
The 18-methylene-1,2-dehydroaspidospermidine (III) was stereospecifically transformed into the schizozygane alkaloid strempeliopine (II) in 16,6 % overall yield.
The asymmetric divergent syntheses of a group of C20 ethyl oxo-functionalized eburnane alkaloids, (−)-eburnaminol (5), (+)-larutenine (6), (−)-terengganensine B (7), (−)-strempeliopine (8), and (−)-terengganensine A (9), have been achieved. The key step in the assembly of the complex ring system of the target molecules is a photoredox catalytic nitrogen-centered radical cascade reaction, which allows