2-Oxabicyclo[3.3.0]octane compounds represented by the following formula (1) (compound (1)); an optical resolver comprising at least one of the compounds (1); a process for producing the compounds (1) which comprises reacting a compound (2) or compound (3) with an alcohol (5) in the presence of an acid catalyst; a method of separating a diastereomer mixture of a compound (1); and a method of optically resolving an alcohol with the optical resolver. [In the formulae, R1 to R10 each represents hydrogen atom, etc.; R11 represents an alkyl group, etc.; R12 represents a hydrocarbon group, etc.; R13 represents a hydrocarbon group, etc.; and A represents acetyl group, etc.]