Abstract: Novel 1.alpha.-hydroxy-24-dehydrovitamin D.sub.3 and its hydroxyl-protected derivatives; novel 1.alpha.-hydroxy-24-dehydroprevitamin D.sub.3 and its hydroxyl-protected derivatives; and novel 1.alpha.,3.beta.-dihydroxycholesta-5,7,24-triene or its hydroxyl-protected derivatives which are key intermediates for preparing the aforesaid compounds. Novel processes for preparing these compounds are also provided. 1.alpha.-Hydroxy-24-dehydrovitamin D.sub.3 has a pharmacological action of controlling the calcium metabolism of warm-blooded animals, and is useful as a prophylactic or therapeutic pharmaceutical for vitamin D deficient disease and related diseases.

Abstract: A process for preparing .beta.,.gamma.-unsaturated aldehydes which comprises dehydrogenating .beta.,.gamma.-unsaturated alcohols in the vapor phase, preferably in the substantial absence of oxygen, using copper having a specific surface area of 0.01 to 1.5 m.sup.2 /g as a catalyst at a temperature of 150.degree. to 300.degree. C. The .beta.,.gamma.-unsaturated aldehydes can be recovered in pure form by distilling the dehydrogenation reaction mixture in the presence of water. The starting .beta.,.gamma.-unsaturated alcohols can be prepared by reacting olefins with formaldehyde or a derivative capable of forming formaldehyde at a temperature of 180.degree. to 400.degree. C. in the absence of a solvent or in the presence of a non-aqueous organic solvent after pre-heating said formaldehyde or derivative to a temperature of 85.degree. to 150.degree. C.

Abstract: A process for the preparation of 2,4,6-trimethylphenol by reacting a phenol of the formula (1) below, ##SPC1##In which R.sub.1 and R.sub.2 each stands for hydrogen atom or methyl groupWith methanol at vapor phase, in the presence of a magnesium oxide-containing catalyst, to methylate the former, the characteristic features residing in that the reaction is performed at the temperatures ranging from 400.degree. to 500.degree.C., and the gaseous mixture composed essentially of the phenol and methanol is contacted with the catalyst at a flow rate not higher than 0.4/hour (sum weight in grams of the phenol and methanol/catalyst's weight in grams/hour).