91797-32-9Relevant academic research and scientific papers
Total Synthesis of the Didemnins; III. - Synthesis of Protected (2R,3S)-Alloisoleucine and (3S,4R,5S)-Isostatine Derivatives - Amino Acids from Hydroxy Acids
Schmidt, Ulrich,Kroner, Matthias,Griesser, Helmut
, p. 832 - 835 (1989)
(2S,3S)-2-Acetoxy-3-methylvaleric acid (3) is prepared from L-isoleucine (2) with 96percent retention of configuration.Compound 3 is converted to optically pure methyl D-alloisoleucinate (7) as its hydrochloride salt, via the methanesulfonate 5 and the azide 6 with 76percent yield and 99.9percent inversion.Subsequent protection-saponification-activation of 7, followed by reaction with the lithium enolate of methyl trimethylsilyl malonate and reduction, yields (3S,4R,5S)-N-(9-fluorenylmethoxycarbonyl)isostatine (12). (3S,4R,5S)-Isostatine is a characteristic unit of the didemnines 1.
General and efficient α-oxygenation of carbonyl compounds by TEMPO induced by single-electron-transfer oxidation of their enolates
Dinca, Emanuela,Hartmann, Philip,Smrcek, Jakub,Dix, Ina,Jones, Peter G.,Jahn, Ullrich
supporting information, p. 4461 - 4482 (2012/10/30)
A generally applicable method for the synthesis of protected α-oxygenated carbonyl compounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N-O bond cleavage to α-hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2-diols or O-protected amino alcohols. The oxygenation of enolates proves to be the most general and effective methodology for the synthesis of O-protected α-oxy carbonyl compounds and nitriles A. The scope and limitations of the electron-transfer-induced radical coupling reaction with TEMPO are presented. The reaction pathways are outlined. Methods for the deprotection to α-hydroxy carbonyl compounds B are provided and discussed. Copyright
ASYMMETRIC WITTIG SIGMATROPIC REARRANGEMENT INVOLVING A CHIRAL AZAENOLATE AS THE MIGRATING TERMINUS. A SIMPLE SYNTHESIS OF (+)-VERRUCARINOLACTONE
Mikami, Koichi,Fujimoto, Katsuhiko,Kasuga, Takashi,Nakai, Takeshi
, p. 6011 - 6014 (2007/10/02)
The diastereo- and/or enantioselection are described in the title rearrangement of the chiral 2-(2-alkenyloxy)methyl 2-oxazolines which eventually provides optically active α-hydroxy γ,δ-unsaturated esters and (+)-verrucarinolactone.
