Abstract: 1.alpha.-hydroxy-vitamin D derivatives represented by formula ##STR1## wherein R.sub.1 represents a hydrogen atom or a hydroxyl group; and R.sub.2 represents a straight-chain or branched C.sub.2 -C.sub.7 alkyl, C.sub.2 -C.sub.7 alkenyl, or C.sub.2 -C.sub.7 alkynyl group. The compounds exhibit calcium metabolism regulating activity and differentiation stimulating activity on tumor cells, and are useful as treating agents for diseases caused by abnormal calcium metabolism, such as osteoporosis and osteomalacia, or as antitumor agents.

Abstract: A 1.alpha.-hydroxy-vitamin D derivative represented by formula (I): ##STR1## wherein R.sub.1 represents a hydrogen atom or a hydroxyl group; and R.sub.2 represents a straight-chain or branched lower alkyl, lower alkenyl or lower alkynyl group, which is substituted with a hydroxyl group, a halogen atom, a cyano group, a lower alkoxy group, an amino group or an acylamino group,is disclosed. The compound exhibits calcium metabolism regulating activity and differentiation stimulating activity on tumor cells, etc. and is useful as a treating agent for diseases caused by abnormal calcium metabolism, such as osteoporosis and osteomalacia, or as an antitumor agent.

Abstract: Vitamin D derivatives of the formula ##STR1## where R.sub.1, R.sub.2 and R.sub.3 which may be the same or different each represents a hydrogen atom or a hydroxyl group; X is an oxygen atom, the group of the formula OR.sub.4 (where R.sub.4 is either a hydrogen atom or a lower alkyl having 4 to 6 carbon atoms that may or may not be substituted by a hydroxyl group), or the group of the formula=N-OR.sub.5 (where R.sub.5 is either a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms that may or may not be substituted by a hydroxyl group, an amino group or a lower alkylamino group having 1 to 3 carbon atoms), provided that the carbon atom at 20-position is linked to X by a single bond when X is the group of the formula OR.sub.4, and by a double bond in other cases, and a process for preparing the derivatives are disclosed.

Abstract: A 1.alpha.-hydroxy vitamin D.sub.3 derivative of the formula: ##STR1## where R.sub.1 is a hydroxyl group, an amino group or the group: OR' (where R' is a lower alkyl group having 1 to 7 carbon atoms that may or may not be substituted by a hydroxyl group, a halogen atom, a cyano group, a lower alkoxy group having 1 to 3 carbon atoms, an amino group, or an acylamino group); R.sub.2 is a hydrogen atom or a hydroxyl group), and a process for preparing the same are disclosed.The compound represented by the formula above has the calcium control action and the ability to induce differentiation in tumor cells and, therefore, are useful as an antitumor agents and a medicine for treating calcium dysbolism-caused diseases.

Abstract: Novel uracil derivatives of the formula ##STR1## (wherein R.sub.1, R.sub.2 R.sub.3 and X are defined in the description) and their pharmaceutically acceptable salts, process for preparing the same and pharmaceutical composition containing the same are disclosed. The uracil derivatives have good antitumor activity and, therefore, are useful as antitumor preparation.