A new and efficient chemoenzymatic route to both enantiomers of alpha '-acetoxy and alpha '-hydroxy-alpha-methoxy cyclic enones

Demir, Ayhan Sıtkı
Caliskan, Z
Aydin, AE
Bicer, I
A chemoenzymatic synthesis of both enantiomers of the pharmacologically interesting alpha'-acetoxy and alpha'-hydroxy-alpha-methoxy cyclic enones starting from alpha-hydroxy cyclic enones is described. Protection of 1,2-diketones, manganese(III) acetate-mediated acetoxylation followed by enzyme-mediated hydrolysis of alpha'-acetoxy enones gives acetoxy enones 3a-d and hydroxy enones 4a-d with high enantiomeric excesses (up to 99%) and good yields. The transesterification of rac-4b in the presence of DMAP afforded (+)-4b and (-)-3b in high enantiomeric excesses (91-94%) and good chemical yields. (c) 2006 Elsevier Ltd All rights reserved.


A new and efficient chemoenzymatic route to both enantiomers of alpha '-acetoxy-alpha-methyl and gamma-hydroxy-alpha-methyl cyclic enones
Demir, Ayhan Sıtkı; Findik, H; Kose, E (Elsevier BV, 2004-03-08)
A chemoenzymatic synthesis of both enantiomers of the pharmacologically interesting alpha'-acetoxy-alpha-methyl and gamma-hydroxy-alpha-methyl cyclic enones starting from alpha-methyl-beta-methoxy cyclic enones is reported. Manganese(Ill) acetate-mediated acetoxylation followed by the enzyme-mediated hydrolysis of alpha'-acetoxy enone provides acetoxy enones 1a and 2a and hydroxy enones 1b and 2b with high enantiomeric excesses in good yields. The reduction of the acetoxy and hydroxy enones furnished both e...
An asymmetric synthesis of both enantiomers of 2,2,2-trifluoro-1-furan-2-yl-ethylamine and 3,3,3-trifluoroalanine from 2,2,2-trifluoro-1-furan-2-yl-ethanone
Demir, Ayhan Sıtkı; Sesenoglu, O; Gercek-Arkin, Z (Elsevier BV, 2001-09-13)
The selective conversion of 2,2,2-trifluoro-1-furan-2-yl-ethanone into (E)- and (Z)-oximes and oxime ethers and subsequent oxazaborolidine-catalyzed enantioselective reduction using different amino alcohols furnished both enantiomers of the important chiral building block 2,2,2-trifluoro-1-furan-2-yl-ethylamine with e.e. of up to 88%. Oxidation of the furan ring afforded both enantiomers of 3,3,3-trifluoroalanine in 91-93% yields.
A bis-Lewis basic 2-aminoDMAP/prolinamide organocatalyst for application to the enantioselective synthesis of Warfarin and derivatives
IŞIK, Murat; Akkoca, H. Ufuk; Akhmedov, I. Mecidoglu; Tanyeli, Cihangir (Elsevier BV, 2016-06-01)
A new chiral sec-amine/amidine-base hybrid catalyst, 2-aminoDMAP/prolinamide, is reported, which is able to catalyze conjugate addition of 4-hydroxycoumarin and various benzylideneacetones, a reaction that directly gives anticoagulant Warfarin and its analogues, with good yields (70-87%) and enantioselectivities (58-72%).
A novel one-pot synthesis of ferrocenyl-substituted 1,2,4-oxadiazoles
Zora, Metin; Kelgokmen, YILMAZ (Elsevier BV, 2014-06-01)
One-pot synthesis of 5-ferrocenyl-1,2,4-oxadiazoles via the reaction between 3-ferrocenylpropynal and amidoximes is described. 3-Ferrocenylpropynal reacts with a variety of amidoximes in the presence of KOH in refluxing dioxane to afford a broad range of 5-ferrocenyl-1,2,4-oxadiazole derivatives. The reaction first produces the corresponding conjugate addition product which, upon cyclization and rearrangement, yields the targeted 1,2,4-oxadiazole. The reaction appears to be general for a diversity of amidox...
Novel enantioselective synthesis of both enantiomers of furan-2-yl Amines and amino acids
Demir, Ayhan Sıtkı; Sesemoglu, O; Ulku, D; Arici, C (Wiley, 2003-01-01)
A new enantioselective synthesis of furan-2-yl amines and amino acids is described, in which the key step is the oxazaborolidine-catalyzed enantioselective reduction of O-benzyl (E)- and (Z)-furan-2-yl ketone oximes to the corresponding chiral amines. The chirality of the furan-2-yl amines is fully controlled by the appropriate choice of the geometrical isomer of the O-benzyl oxime. Oxidation of the furan ring furnished amino acids in high yields.
Citation Formats
A. S. Demir, Z. Caliskan, A. Aydin, and I. Bicer, “A new and efficient chemoenzymatic route to both enantiomers of alpha ‘-acetoxy and alpha ’-hydroxy-alpha-methoxy cyclic enones,” TETRAHEDRON-ASYMMETRY, pp. 786–791, 2006, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/57472.