Process for producing optically active alpha-substituted cysteine or salt thereof, intermediate therefor, and process for producing the same

A process for producing an optically active α-substituted cysteine represented by general formula (6) or a salt thereof:

• (where * represents an asymmetric carbon atom;
• and R3 represents an optionally substituted linear, branched, or cyclic C1-C20 alkyl group, an optionally substituted linear, branched, or cyclic C2-C20 alkenyl group, an optionally substituted linear, branched, or cyclic C2-C20 alkynyl group, an optionally substituted linear, branched, or cyclic C3-C20 alkoxycarbonylalkyl group, an optionally substituted C7-C30 aralkyl group, or an optionally substituted C4-C30 heteroaralkyl group), the process comprising a step of hydrolyzing an optically active thiazoline compound represented by general formula (1):
• (where * and R3 are the same as above;
• R1 represents an optionally substituted linear, branched, or cyclic C1-C10 alkyl group or an optionally substituted linear, branched, or cyclic C1-C10 alkylsilyl group;
• and R2 represents an optionally substituted C6-C30 aryl group or an optionally substituted linear, branched, or cyclic C1-C20 alkyl group).

An optically active thiazoline compound represented by general formula (7):

• (where * represents an asymmetric carbon atom;
• R1 represents an optionally substituted linear, branched, or cyclic C1-C10 alkyl group or an optionally substituted linear, branched, or cyclic C1-C10 alkylsilyl group;
• R2 represents an optionally substituted C6-C30 aryl group or an optionally substituted linear, branched, or cyclic C1-C20 alkyl group;
• and R7 represents an optionally substituted linear, branched, or cyclic C2-C20 alkyl group, an optionally substituted linear, branched, or cyclic C2-C20 alkenyl group, an optionally substituted linear, branched, or cyclic C2-C20 alkynyl group, an optionally substituted linear, branched, or cyclic C3-C20 alkoxycarbonylalkyl group, an optionally substituted C7-C30 aralkyl group, or an optionally substituted C4-C30 heteroaralkyl group).