Patent ID: 7737274

Claim:
A method for producing a phenylalanine derivative(s) having a quinazolinedione ring of the following formula (5), comprising steps of reacting an acylphenylalanine derivative(s) of formula (1): wherein R1 represents a phenyl group which may have a substituent(s) or a pyridyl group which may have a substituent(s), R2 represents an alkyl group which may have a substituent(s), and the derivative(s) is in a salt(s) with chemically acceptable acid(s) or free form(s), with a carbonyl group-introducing reagent(s) and an anthranilic acid derivative(s) of formula (2): wherein R3 represents a dialkylamino group; R4 represents a hydrogen atom, an alkyl group or a benzyl group which may have a substituent(s); and R5 represents an alkyl group or an alkylcarbonyl group, and the derivative(s) is in a salt(s) with chemically acceptable acid(s) or free form(s), to form an asymmetric urea intermediate(s) of formula (3): wherein R1 to R5 are defined above; making the asymmetric urea intermediate(s) into a quinazolinedione compound(s) of formula (4) in the presence of a base(s): wherein R1 to R4 are defined above; and when R4 represents a hydrogen atom in the obtained quinazolinedione compound(s) of the formula (4), N-alkylating a quinazolinedione ring amide of the quinazolinedione compound(s) with an N-alkylation agent(s) to form the phenylalanine derivative(s) having a quinazolinedione skeleton of formula (5): wherein R1 to R3 are defined above, R4 represents an alkyl group or a benzyl group which may have a substituent(s).