One-pot multiple reactions: asymmetric synthesis of 2,6-cis-disubstituted piperidine alkaloids from chiral aziridine
作者:Nagendra Nath Yadav、Jihye Choi、Hyun-Joon Ha
DOI:10.1039/c6ob00806b
日期:——
A divergent, new, and highly stereoselective synthesis of cis-2,6-disubstituted piperidine natural products including isosolenopsins, deoxocassine, and spectaline was achieved from chiral aziridine decorated with appropriate alkyl chains for isosolenopsins or alkynyl groups for deoxocassine and spectaline at C2. The characteristic feature of this synthesis is one-pot sequential reactions under atmospheric
Controlled reduction of 5-alkyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide: enantioselective synthesis of (−)-dihydropinidine and (+)-indolizidine 167B
作者:Luis F. Roa、Dino Gnecco、Alberto Galindo、Joel L. Terán
DOI:10.1016/j.tetasy.2004.09.030
日期:2004.11
reduction of (+)-(3R,5S)-5-methyl- and (+)-(3R,5S)-5-n-propyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide 1 and 2 to generate (3R,5S)-5-methyl- and (3R,5S)-5-n-propyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridine 3 and 4, respectively, is reported. In addition, an enantioselectivesynthesis of (−)-(2R,6S)-dihydropinidine and (+)-(2S,6S)-indolizidine167B starting from
(+)-(3 R,5 S)-5-甲基-和(+)-(3 R,5 S)-5- n-丙基-3-苯基-2,3,5,6的受控还原,7,8-六氢-恶唑并[3,2- a ]吡啶-4-基碘鎓碘化物1和2生成(3 R,5 S)-5-甲基-和(3 R,5 S)-5- n据报道,分别是-丙基-3-苯基-2,3,5,6,7,8-六氢-恶唑并[3,2- a ]吡啶3和4。另外,(-)-(2 R,6 S)-二氢吡啶和(+)-(2获得了分别从3和4开始的S,6S)-吲哚唑烷167B 。
Diastereoselective Addition of Grignard Reagents to Chiral 1,3-Oxazolidines Having a N-Diphenylmethyl Substituent.
Chiral 1, 3-oxazolidines having a diphenylmethyl group at the 3-position of the oxazolidine ring as a bulky substituent were synthesized. The reaction of Grignard reagents with the chiral 1, 3-oxazolidines afforded the corresponding amines with very high diastereoselectivity. Furthermore, the method for the synthesis of optically active amines was applied to the asymmetric synthesis of (-)-dihydropinidine, a piperidine alkaloid.
Aldimines of 2,3,4,6-tetra-0-pivaloyl-β-D-galactosylamine react with 1-methoxy-3-trimethylsilyloxybuta-1,3-diene in a Mannich-Michael condensation reaction sequence to give 2-substituted N-galactosyl-5,6-dehydropiperidin-4-ones 3 with high diastereoselectivity. The X-ray analysis of the 2-propyl derivative 3a proved (R)-configuration of the major diastereomer and led to the correction of our earlier assignment of configuration for (-)-coniine hydrochloride 9a obtained from this intermediate. Despite their low reactivity, these enaminones 3 can be converted into chiral 2,6-cis-disubstituted piperidinones 12 with high stereoselectivity by reaction with organocuprates in combination with hard electrophiles. Enantiomerically pure alkaloids such as (-)-dihydropinidine and gephyrotoxine 167B have been synthesized according to this methodology.
Regio- and Stereoselective Monoamination of Diketones without Protecting Groups
作者:Robert C. Simon、Barbara Grischek、Ferdinand Zepeck、Andreas Steinreiber、Ferdinand Belaj、Wolfgang Kroutil
DOI:10.1002/anie.201202375
日期:2012.7.2
Hitting the right target: Differentiation between two keto moieties was accomplished by a regio‐ and enantioselective bioamination employing ω‐transaminases. Using 1,5‐diketones as substrates gave access to the opticallypure 2,6‐disubstituted piperidine scaffold. The approach allowed the shortest synthesis of the alkaloid dihydropinidine, as well as its enantiomer, by choosing an appropriate ω‐transaminase