Norvaline Derivative and Method for Preparation Thereof

A norvaline derivative of the formula [I]:

• [wherein
• X is —CH2—, —O—, —S— or a single bond;
• Ar is an optionally substituted aryl or an optionally substituted lower cycloalkyl;
• n is an integer of 0 to 2;
• R1 and R2 are the following (i), (ii) or (iii):
• (i) each is independently a hydrogen atom or a lower alkyl;
• (ii) R1 and R2 are combined together to form a lower alkylene;
• or
• (iii) R1 is a hydrogen atom or a lower alkyl and R2 is combined together with R4 or R6 to form a lower alkylene, when R is
• R3 and R4 are the following (i), (ii) or (iii):
• (i) each is independently a hydrogen atom or a lower alkyl;
• (ii) R3 and R4 are combined together to form a lower alkylene;
• or
• (iii) R3 is a hydrogen atom or a lower alkyl and R4 is combined together with R2 or R6 to form a lower alkylene, when R is
• R is
• or —OR7;
• R5 and R6 are the following (i), (ii) or (iii):
• (i) each is independently a lower alkyl optionally substituted with hydroxyl group(s), or a hydrogen atom;
• (ii) R5 and R6 are combined together with the adjacent nitrogen atom to form an optionally substituted nitrogen-containing aliphatic 5- to 6-membered heterocyclic group;
• (iii) R5 is a lower alkyl optionally substituted with hydroxyl group(s), or a hydrogen atom, and R6 is combined together with R2 or R4 to form a lower alkylene;
• R7 is a lower alkyl;
• provided that when R5 and R6 are combined together with the adjacent nitrogen atom to form a morpholine ring, then Ar has at least one substituent other than halogen atom, methoxy or phenyl;
• and when R is —OR7 and X is a single bond, then Ar is an optionally substituted phenyl, an optionally substituted naphthyl or an optionally substituted lower cycloalkyl],
• or a pharmaceutically acceptable salt thereof.