Compound useful for manufacturing salacinol, method for manufacturing the compound, method for manufacturing salacinol, methods for protecting and deprotecting diol group, and protective agent for diol group

A compound represented by Formula (1),

• (in the formula, R1a and R1b are the same as or different from each other and each represent a hydrogen atom or a carboxy protective group;
• and each of R2 and R3 is a hydroxy group, R2 is a group represented by Formula (2) and R3 is a group represented by Formula (3),
• (in the formula, R4a, R4b, and R4c are the same as or different from each other and each represent a hydrogen atom or a hydroxy protective group;
• and * represents a binding position), and
• (in the formula, * has the same definition as described above),
• or R2 and R3 are bonded to each other and represent a group represented by Formula (4),
• *—O—X1—O—* (4)
• (in the formula, X1 is a group represented by Formula (5) or a group represented by Formula (6);
• and * has the same definition as described above),
• (in the formula, R5 is an aryl group which may be substituted;
• and * has the same definition as described above), and
• (in the formula, * has the same definition as described above)).