Fluorination of (E)-.beta.-(Fluoromethylene)-m-Tyrosine: Regioselective Synthesis of 4-Fluoro-(E)-.beta.-(Fluoromethylene)-m-Tyrosine
摘要:
Fluorination of (R)- and (S)-(E)-beta-(fluoromethylene)-m-tyrosine (1) by acetyl hypofluorite yielded a mixture of the corresponding 2-fluoro- (2a), 6-fluaro- (2b), 4-fluoro- (2c), and 2,6-difluoro- (2d) derivatives along with a pair of diastereomeric products of addition across the vinylic double bond. A regioselective synthesis of 4-fluoro-(E)-beta-(fluoromethylene)-m-tyrosine has also been developed based on a fluorodestannylation reaction with elemental fluorine followed by acid hydrolysis. This reaction sequence yielded minor byproducts, namely, 4-fluoro-(Z)-beta-(fluoromethylene)-m-tyrosine (II), 4,6-difluoro- and 2,4-difluoro-(E)-beta-(fluoromethylene)-m-tyrosines (12a and 12b). All these products were completely separated by semipreparative HPLC and fully characterized by NMR and mass spectroscopy. Single crystal X-ray crystallographic analyses of 2-fluoro-, 4-fluoro-, and 6-fluoro-(E)-beta-(fluoromethylene)-m-tyrosines unequivocally established the structures of these amino acids.
(E) and (Z)-β-fluoromethylene-m-tyrosines: Resolution and determination of configuration
摘要:
The geometrical isomers of beta-fluoromethylene-m-tyrosine (E and Z) were prepared and the R and S enantiomers of the biologically active (E)-isomer were separated with an enantiomeric excess >95% by the kinetic resolution of the racemic mixture using the enzyme alpha-chymotrypsin. The enantiomers of the (Z)-isomer were obtained by an acid catalyzed isomerization reaction. The absolute configurations of the isolated enantiomers were determined based on their CD spectral characteristics and chiral HPLC behavior. The R and S enantiomers of (E)-beta-fluoromethylene-m-tyrosine were also analyzed by single crystal X-ray crystallography.
Fluorination of (E)-.beta.-(Fluoromethylene)-m-Tyrosine: Regioselective Synthesis of 4-Fluoro-(E)-.beta.-(Fluoromethylene)-m-Tyrosine
作者:Goran Lacan、N. Satyamurthy、Jorge R. Barrio
DOI:10.1021/jo00106a038
日期:1995.1
Fluorination of (R)- and (S)-(E)-beta-(fluoromethylene)-m-tyrosine (1) by acetyl hypofluorite yielded a mixture of the corresponding 2-fluoro- (2a), 6-fluaro- (2b), 4-fluoro- (2c), and 2,6-difluoro- (2d) derivatives along with a pair of diastereomeric products of addition across the vinylic double bond. A regioselective synthesis of 4-fluoro-(E)-beta-(fluoromethylene)-m-tyrosine has also been developed based on a fluorodestannylation reaction with elemental fluorine followed by acid hydrolysis. This reaction sequence yielded minor byproducts, namely, 4-fluoro-(Z)-beta-(fluoromethylene)-m-tyrosine (II), 4,6-difluoro- and 2,4-difluoro-(E)-beta-(fluoromethylene)-m-tyrosines (12a and 12b). All these products were completely separated by semipreparative HPLC and fully characterized by NMR and mass spectroscopy. Single crystal X-ray crystallographic analyses of 2-fluoro-, 4-fluoro-, and 6-fluoro-(E)-beta-(fluoromethylene)-m-tyrosines unequivocally established the structures of these amino acids.
(E) and (Z)-β-fluoromethylene-m-tyrosines: Resolution and determination of configuration
作者:Goran Laćan、N Satyamurthy、Jorge R Barrio
DOI:10.1016/0957-4166(95)00036-o
日期:1995.2
The geometrical isomers of beta-fluoromethylene-m-tyrosine (E and Z) were prepared and the R and S enantiomers of the biologically active (E)-isomer were separated with an enantiomeric excess >95% by the kinetic resolution of the racemic mixture using the enzyme alpha-chymotrypsin. The enantiomers of the (Z)-isomer were obtained by an acid catalyzed isomerization reaction. The absolute configurations of the isolated enantiomers were determined based on their CD spectral characteristics and chiral HPLC behavior. The R and S enantiomers of (E)-beta-fluoromethylene-m-tyrosine were also analyzed by single crystal X-ray crystallography.