The C-24 configurations of (22E)-25,28-dimethylstigmasta-5,22,28-trien-3p-ol (1) and 25,28-dimethylstigmasta-5,28-dien-3β-ol (2), isolated from the sponge Topsentia ophiraphidites in our previous work, were determined to be both S, through the synthesis of stereodefined (24S)- and (24R)-epimers of 1 and 2 and comparison of the 1H and 13C NMR spectroscopic data. In addition, the C-24 configurations of the marine sterols having the same structures as 1 and 2 and their derivatives were also assigned for the first time by NMR comparison.
CalderonG.J., CastellanosL., DuqueC., EchigoS., HaraN., FujimotoY. (2004) Ophirasterol, a new C31 sterol from the marine sponge Topsentia ophiraphidites. Steroids, 69, 93–100.
2.
EchigoS., CastellanosL., DuqueC., UekusaH., HaraN., FujimotoY. (2011) C-24 stereochemistry of marine sterols: (22E)-24-ethyl-24-methylcholesta-5,22-dien-3β-ol and 24-ethyl-24-methylcholest-5-en-3β-ol. Journal of the Brazilian Chemical Society, 22, 995–1002.
3.
EchigoS., HaraN., CalderonG.J., DuqueC., FujimotoY. (2006) C-24 Stereochemistry of marine sterols: (22E)-24-isopropenyl-22-dehydro-cholesterol and 24-isopropenylcholesterol. Chemical and Pharmaceutical Bulletin, 54, 1473–1477.
4.
KerrR.G., FossC., MatsunagaS., FusetaniN. (1997) Isolation and structure elucidation of epipolasterol and 22,23-dihydroepipolasterol from the marine sponge Epipolasis sp. Comparative Biochemistry and Physiology, Part B: Biochemistry and Molecular Biology, 117, 561–563.
5.
Makar'evaT.N., IsakovV.V., StonikV.A. (1990) Steroid compounds of marine sponges. XI. Steroids of the Australian sponge Trachyopsis sp. Chemistry of Natural Compounds, 26, 172–174.
6.
LiX., DjerassiC. (1983) Minor and trace sterols in marine invertebrates 40. Structure and synthesis of axinyssasterol, 25-methylfucosterol and 24-ethyl-24-methylcholesterol - novel sponge sterols with highly branched side chains. Tetrahedron Letters, 24, 665–668.
7.
IshibashiM., YamagishiE., KobayashiJ. (1997) Topsentinols A-J, new sterols with highly branched side chains from marine sponge Topsentia sp. Chemical and Pharmaceutical Bulletin, 45, 1435–1438.
8.
(a) TakahashiT., YamadaH., TsujiJ. (1981) Stereoselective synthesis of steroid side chains: a route to de-AB-cholestan-9-one. Journal of the American Chemical Society, 103, 5259–5261;(b) Takahashi T, Ootake A, Yamada H, Tsuji J. (1985) Stereoselective reduction of the steroidal 23-en-22-one: a route to the side chain of the plant growth promoter brassinolide. Tetrahedron Letters, 26, 69–72; (c) Yamada H. (1990) Doctor Dissertation, Tokyo Institute of Technology.
9.
WiersigJ.R., Waespe-SarcevicN., DjerassiC. (1979) Stereospecific synthesis of the side chain of the steroidal plant sex hormone oogoniol. The Journal of Organic Chemistry, 44, 3374–3382.
10.
OhtaniI., KusumiT., KashmanY., KakisawaH. (1991) High-field FT NMR application of Mosher's method. The absolute configurations of marine terpenoids. Journal of the American Chemical Society, 113, 4092–4096.
11.
(a) KhripachV.A., ZhabinskiiV.N., KonstantinovaO.V., KhripachN.B., AntonchickA.P., SchneiderB. (2002) [3,3]-Claisen rearrangements in 24α-methyl steroid synthesis: Application to campesterol, crinosterol, and Δ25-crinosterol side chain construction. Steroids, 67, 597–603;(b) Sucrow W, Schubert B, Richter W, Slopianka M. (1971) Stereochemie einer Claisen-Umlagerung in der Sterin-Seitenkette. Chemische Berichte, 104, 3689–3703.
