Stereoselective synthesis and hormonal activity of novel dafachronic acids and naturally occurring steroids isolated from coralsElectronic supplementary information (ESI) available: 1H and 13C NMR spectra of compounds 9-11, 13, 16, 20 and 23. 2D NMR spectra (COSY, HSQC, HMBC and NOESY) of compound 20. CCDC 867379 and 867380. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2ob25394a

A stereoselective synthesis of (25 S )-Δ 1 -, (25 S )-Δ 1,4 -, (25 S )-Δ 1,7 -, (25 S )-Δ 8(14) -, (25 S )-Δ 4,6,8(14) -dafachronic acid, methyl (25 S )-Δ 1,4 -dafachronate and (25 S )-5α-hydroxy-3,6-dioxocholest-7-en-26-oic acid is described. (25 S )-Δ 1,4 -Dafachronic acid and its methyl ester are natural products isolated from corals and have been obtained by synthesis for the first time. (25 S )-5α-Hydroxy-3,6-dioxocholest-7-en-26-oic acid represents a promising synthetic precursor for cytotoxic marine steroids. A series of novel dafachronic acids has been synthesized and their hormonal activity has been tested by rescuing worms from dauer arrest. (25 S )-Δ 1,4 -Dafachronic acid was isolated previously from the Indonesian soft coral Minabea sp.