Process for production of aspartyl dipeptide ester derivative, novel production intermediate therefor, and process for production thereof

A process for producing a compound of formula (2), which comprises converting a carboxyl group in a compound of formula (4) into a formyl group

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• wherein, R1, R2, R3, R4 and R5 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms, and a hydroxyalkyloxy group having 2 or 3 carbon atoms.

A process for producing a compound of formula (1), which comprises selectively reducing a carbon-carbon double bond in a compound of the formula (2),

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• wherein R1, R2, R3, R4 and R5 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms, and a hydroxyalkyloxy group having 2 or 3 carbon atoms.

A process for producing a compound of formula (1), which comprises:

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• converting a carboxyl group in a compound of formula (5) into a formyl group,
• wherein R1, R2, R3, R4 and R5 are independently selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms, and a hydroxyalkyloxy group having 2 or 3 carbon atoms.

A process for producing a 3-(3-hydroxy-4-methoxyphenyl) propionaldehyde, which comprises:

• selectively reducing a carbon-carbon double bond of 3-hydoroxy-4-methoxycinnamaldehyde;
• or converting a carboxyl group of 3-(3-hydoroxy-4-methoxyphenyl)propionic acid into a formyl group.

A process for producing a N-[N-[3-(3-hydroxy-4-methoxyphenyl) propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester, which comprises reductively alkylating 3-(3-hydroxy-4-methoxyphenyl) propionaldehyde with an aspartame.

3-(3-hydroxy-4-methoxyphenyl) propionaldehyde.