6036-75-5Relevant articles and documents
Chemo-, regio-, and stereoselective silver-catalyzed aziridination of dienes: Scope, mechanistic studies, and ring-opening reactions
Llaveria, Josep,Beltrán, álvaro,Sameera,Locati, Abel,Díaz-Requejo, M. Mar,Matheu, M. Isabel,Castillón, Sergio,Maseras, Feliu,Pérez, Pedro J.
, p. 5342 - 5350 (2014/05/06)
Silver complexes bearing trispyrazolylborate ligands (Tpx) catalyze the aziridination of 2,4-diene-1-ols in a chemo-, regio-, and stereoselective manner to give vinylaziridines in high yields by means of the metal-mediated transfer of NTs (Ts = p-toluensulfonyl) units from PhI=NTs. The preferential aziridination occurs at the double bond neighboring to the hydroxyl end in ca. 9:1 ratios that assessed a very high degree of regioselectivity. The reaction with the silver-based catalysts proceeds in a stereospecific manner, i.e., the initial configuration of the C=C bond is maintained in the aziridine product (cis or trans). The degree of regioselectivity was explained with the aid of DFT studies, where the directing effect of the OH group of 2,4-diene-1-ols plays a key role. Effective strategies for ring-opening of the new aziridines, deprotection of the Ts group, and subsequent formation of β-amino alcohols have also been developed.
Efficient silver-catalyzed regio- and stereospecific aziridination of dienes
Llaveria, Josep,Beltran, Alvaro,Diaz-Requejo, M. Mar,Perez, Pedro J.,Matheu, M. Isabel,Castillon, Sergio
supporting information; experimental part, p. 7092 - 7095 (2010/11/05)
Nitrene transfer: Unsymmetric dienes bearing a terminal hydroxy group can be regio- and stereospecifically converted into vinylaziridines upon nitrene transfer from PhINTs using a silver-based catalyst. Stoichiometric mixtures of dienes and PhINTs were employed at low catalyst loadings (0.5□%; see scheme). The method has been applied to the synthesis of (±)-sphingosine and gave good yields in a three-step procedure. Ts=4-toluenesulfonyl.
Lipase-catalyzed enantiomeric resolution of ceramides 1
Bakke, Mikio,Takizawa, Masahiro,Sugai, Takeshi,Ohta, Hiromichi,Herold
, p. 6929 - 6938 (2007/10/03)
Lipase-catalyzed enantiomeric kinetic resolution of ceramides related to C16-sphinganine and C18-sphingenine is described. Two hydroxy groups in readily available racemic N-stearoyl-erythroC16-sphinganine were acetylated, and several kinds of lipases were screened for the hydrolysis of this substrate. Among them, a Burkholderia cepacia lipase (SC lipase A, Sumitomo Chemical Co., Ltd.) showed the highest reactivity and enantioselectivity. The rate of hydrolysis and selectivity were greatly affected by some additives. Especially, the combined use of a detergent, Triton X-100, and the solid support, Florisil, for immobilization showed the highest enantioselectivity (E = ca. 170), although the reaction rate turned low. Introduction of a double bond into the substrate (N-stearoyl-erythro-Cis-sphingenine) also retarded the hydrolysis. By utilizing the preferential hydrolysis of the acetate on the primary hydroxy group, another advantageous feature of this enzyme-catalyzed reaction, the resulting product could directly be used as the glycosyl acceptor for cerebroside synthesis.