[3 + 4] and [3 + 5] Annulation Reactions of .alpha.-(Phenylthio)Dicarbonyl Electrophiles with Bis(trimethylsilyl) Enol Ethers: Synthesis of Highly Functionalized Medium Ring Carbocycles
摘要:
The [3 + 4] and [3 + 5] annulations of bis(trimethylsilyl) enol ethers with 1,4- and 1,5-dicarbonyl electrophiles bearing alpha-phenylthio substituents leads to the formation of bicyclic [3.2.1] and [3.3.1] ethers with good regiochemical and stereochemical control, Subsequent oxidation of the phenylthio moiety followed by reduction with SmI2 constitutes a high-yielding and regioselective process for cleavage of the bridging ether linkage. The overall strategy provides a synthetic pathway for the synthesis of highly functionalized medium ring carbocycles.
Nucleotide C4′ radical fragmentation is base-dependent
摘要:
Nucleotide C4' radicals undergo radical ionic fragmentation with expulsion of the 3'-phosphate giving a 3',4'-radical cation. With a series of mononucleotides it is shown that the rate of this fragmentation is a function of the base (T similar to G > ABz > A similar to C) with the least basic, less-hydrogen bonded nucleotides fragmenting more rapidly in aqueous methanol. (C) 1997 Elsevier Science Ltd.
Synthesis of Cyclic Bis(trimethysilyl) Enol Ethers and Their [3 + 4] and [3 + 5] Annulation Reactions with Dicarbonyl Electrophiles. Access to Highly Functionalized Tricyclic Ethers Possessing Trans Intrabridgehead Stereochemistry
作者:Gary A. Molander、Bernard Bessières、Paul R. Eastwood、Bruce C. Noll
DOI:10.1021/jo9902547
日期:1999.5.1
The synthesis of cyclic bis(trimethylsilyl) enol ethers from cycloalkanone carboxylates is described. The [3 + 4] and [3 + 5] annulation reactions of these bis(dinucleophilic), synthons with various 1,4- and 1,5-dicarbonyl electrophiles leads to the formation of tricyclic keto ethers with good regio- and stereochemical control. An interesting trans intrabridgehead stereochemistry is observed when using bis(trimethylsilyl) enol ethers derived from nine- to 12-membered ring beta-keto esters.
[3 + 4] and [3 + 5] Annulation Reactions of .alpha.-(Phenylthio)Dicarbonyl Electrophiles with Bis(trimethylsilyl) Enol Ethers: Synthesis of Highly Functionalized Medium Ring Carbocycles
作者:Gary A. Molander、Paul R. Eastwood
DOI:10.1021/jo00131a013
日期:1995.12
The [3 + 4] and [3 + 5] annulations of bis(trimethylsilyl) enol ethers with 1,4- and 1,5-dicarbonyl electrophiles bearing alpha-phenylthio substituents leads to the formation of bicyclic [3.2.1] and [3.3.1] ethers with good regiochemical and stereochemical control, Subsequent oxidation of the phenylthio moiety followed by reduction with SmI2 constitutes a high-yielding and regioselective process for cleavage of the bridging ether linkage. The overall strategy provides a synthetic pathway for the synthesis of highly functionalized medium ring carbocycles.
Nucleotide C4′ radical fragmentation is base-dependent
作者:David Crich、Xue-Sheng Mo
DOI:10.1016/s0040-4039(97)10249-0
日期:1997.11
Nucleotide C4' radicals undergo radical ionic fragmentation with expulsion of the 3'-phosphate giving a 3',4'-radical cation. With a series of mononucleotides it is shown that the rate of this fragmentation is a function of the base (T similar to G > ABz > A similar to C) with the least basic, less-hydrogen bonded nucleotides fragmenting more rapidly in aqueous methanol. (C) 1997 Elsevier Science Ltd.