23-yne-vitamin D

To provide a novel vitamin D 3 derivative useful as a therapeutic agent for osteoporosis. Provided is a vitamin D 3 derivative represented by the following formula (1) or a medicinally acceptable solvate thereof: wherein R 1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkylcarbonyloxyalkyl group with each alkyl having 1 to 6 carbon atoms, or an arylcarbonyloxyalkyl group with the aryl having 6 to 10 carbon atoms and the alkyl having 1 to 6 carbon atoms; R 2 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms or, together with the other R 2 and the carbon atom to which they are bound to, may form a cyclic alkyl group having 3 to 6 carbon atoms; R 3 represents an alkyl group having 1 to 6 carbon atoms or, together with the other R 3 and the carbon atom to which they are bound to, may form a cyclic alkyl group having 3 to 6 carbon atoms; X represents an oxygen atom or a methylene group; and n represents an integer of 1 or 2.