Asymmetric Synthesis of 2-Alkyl(Aryl)-2,3-dihydro-4-pyridones by Addition of Grignard Reagents to Chiral 1-Acyl-4-methoxypyridinium Salts
作者:Daniel L. Comins、Sajan P. Joseph、R. Richard Goehring
DOI:10.1021/ja00090a019
日期:1994.6
Grignard addition to a chiral 1-acyl-4-methoxypyridinium salt provides synthetically useful 2-alkyl(aryl)-2,3-dihydro-4-pyridones in high diastereomeric excess
Addition of Indolyl and Pyrrolyl Grignard Reagents to 1-Acylpyridinium Salts
作者:Jeffrey T. Kuethe、Daniel L. Comins
DOI:10.1021/jo049943v
日期:2004.4.1
Certain indolyl and pyrrolylGrignardreagents add to 1-acyl salts of 4-methoxy-3-(triisopropylsilyl)pyridine to give the corresponding 1-acyl-2-heteroaryl-2,3-dihydro-4-pyridones in good to high yield. When the 1-acyl group contained a chiral auxiliary, (±)-trans-2-(α-cumyl)cyclohexyloxy, addition of the indolylGrignards resulted in a separable mixture of diastereomeric 2,3-dihydro-4-pyridones.
Concise and highly stereocontrolled total syntheses of racemic and enantiopure frog alkaloid 205B (1) were accomplished in 11 steps from 4-methoxypyridines 6 and 7 in overall yields of 8 and 8%, respectively. The assembly of the core of the natural product relies on a stereoselective Tsuji–Trost allylic amination reaction and a ring-closing metathesis. The synthesis features the use of an N-acylpyridinium
Asymmetric Synthesis of All the Known Phlegmarine Alkaloids
作者:Bradley H. Wolfe、Adam H. Libby、Rima S. Al-awar、Christopher J. Foti、Daniel L. Comins
DOI:10.1021/jo1019688
日期:2010.12.17
The asymmetric synthesis of all four of the known natural phlegmarines and one synthetic derivative has been accomplished in 19−22 steps from 4-methoxy-3-(triisopropylsilyl)pyridine. Chiral N-acylpyridinium salt chemistry was used twice to set the stereocenters at the C-9 and C-2′ positions of the phlegmarine skeleton. Key reactions include the use of a mixed Grignard reagent for the second N-acylpyridinium
Enantiopure <i>N</i>-Acyldihydropyridones as Synthetic Intermediates: Asymmetric Synthesis of (−)-Septicine and (−)-Tylophorine
作者:Daniel L. Comins、Xinghai Chen、Lawrence A. Morgan
DOI:10.1021/jo9711495
日期:1997.10.1
A concise asymmetric synthesis of (-)-septicine (1) and (-)-tylophorine (2) was accomplished with a high degree of stereocontrol in eight and nine steps, respectively. Addition of 4-(1-butenyl)magnesium bromide to 1-acylpyridinium salt 3, prepared in situ from 4-methoxy-3-(triisopropylsilyl)pyridine and the chloroformate of (-)-trans-2-(alpha-cumyl)cyclohexanol, gave a 91% yield of diastereomerically