Two acetylenic steroids, cholest-5-en-23-yn-3β-ol (5) and 26,27-dinorcholest-5-en-23-yn-3β-ol (3), and another unsaturated steroidalcohol, stigmasta-5,23-dien-3β-ol (7), were isolated from the sponge Calyx nicaaensis. The structures of these two acetylenic steroids were established by synthesis. Several attempts to synthesize the marine steroids alcohol calysterol (1), with a cyclopropene-containing side chain, starting from cholest-5-en-23-yn-3β-ol are also recorded. Addition of ethyl-diazo-acetate to the triple bond was performed, but the reduction to the methyl derivative yielded decomposition products.