Acetal-type releasable polyoxyethylene derivative, production method thereof and acetal-type releasable polyoxyethylene conjugate

An acetal-type releasable polyoxyethylene conjugate, represented by the following Formula (7), (8), (9) or (10), and cleaved under a physiological condition,

• wherein
• B2 represents a hydrogen atom or —C(R1)(R2)OC(O)NHD1,
• D1 represents a residue obtained by removing an amino group that constitutes a carbamate bond from an amino group contained in a biofunctional molecule,
• P2 represents a polyoxyethylene derivative having a dehydroxylated group, or a conjugate of a biofunctional molecule and a polyoxyethylene derivative having a dehydroxylated group,
• w represents an integer of 1 to 8,
• R1, R2, R3, R4, R5 and R11 each independently represent a hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom,
• R6, R7, R8, R9 and R10 each independently represent an electron-withdrawing substituent, an electron-donating substituent, or a hydrogen atom, and
• m represents 0 or 1.