A phosphorus compound of formula (1): wherein R1 denotes a hydrogen atom or a hydroxy protective group; R2 denotes a group defined by the following formula (R2-1) or (R2-2); R3, R4, R5, and R6 may be the same or different and independently denote a hydrogen atom, an alkyl group, an alkoxy group, an acyloxy group, a halogen atom, a haloalkyl group, or a dialkylamino group; two among R3, R4, R5, and R6 may form an aromatic ring optionally having a substituent group, and two among R3, R4, R5, and R6 may form a methylene chain optionally having a substituent group or a (poly)methylenedioxy group optionally having a substituent group: wherein (R2-1) and (R2-2), R7 denotes an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, or an aryloxy group; R8 and R9 independently denote a hydrogen atom, an alkyl group, or an aryl group; z denotes a divalent group; and a denotes an integer of 0 or 1.