The invention relates to an overall enantio-specific synthesis of 4-chlorokynurenine compounds, in particular L-4-chlorokynurenine, with improved yields. Large-scale syntheses are disclosed. The invention also relates to novel intermediates in the synthesis of L-4-chlorokynurenine.

The invention relates to an overall enantio-specific synthesis of 4-chlorokynurenine compounds, in particular L-4-chlorokynurenine, with improved yields. Large-scale syntheses are disclosed. The invention also relates to novel intermediates in the synthesis of L-4-chlorokynurenine.

The present invention provides a composition comprising anti-1-amino-3-.sup.18F-fluorocyclobutyl-1-carboxylic acid (.sup.18F-FACBC) having an improved impurity profile compared with previous such compositions. Also provided is a method to obtain said composition.

The present invention provides a composition comprising anti-1-amino-3-.sup.18F-fluorocyclobutyl-1-carboxylic acid (.sup.18F-FACBC) having an improved impurity profile compared with previous such compositions. Also provided is a method to obtain said composition.

The present invention relates to a process for the preparation of Droxidopa by means of an improved enzymatic reduction of a compound of formula (II): (II), wherein R.sup.1, R.sup.2 is independent hydrogen, acetyl, R.sup.3 is hydrogen, a C1-C4 linear or branched alkyl group and R.sup.4 is hydrogen or an amine protecting group.

##STR00001##

The present invention relates to a process for the preparation of Droxidopa by means of an improved enzymatic reduction of a compound of formula (II): (II), wherein R.sup.1, R.sup.2 is independent hydrogen, acetyl, R.sup.3 is hydrogen, a C1-C4 linear or branched alkyl group and R.sup.4 is hydrogen or an amine protecting group.

##STR00001##

The present invention relates to a process for the preparation of Droxidopa by means of an improved enzymatic reduction of a compound of formula (II): (II), wherein R.sup.1, R.sup.2 is independent hydrogen, acetyl, R.sup.3 is hydrogen, a C1-C4 linear or branched alkyl group and R.sup.4 is hydrogen or an amine protecting group.

##STR00001##

Provided herein are processes, compounds and compositions for making (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid. Also provided herein a pharmaceutical compositions containing (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid.

Provided herein are processes, compounds and compositions for making (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid. Also provided herein a pharmaceutical compositions containing (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid.

Provided herein are processes, compounds and compositions for making (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid. Also provided herein a pharmaceutical compositions containing (S)-3-amino-4-(difluoromethylenyl)cyclopent-1-ene-1-carboxylic acid.