The Preparation of 24-Keto and 24-Hydroxycholesterol and Certain Derivatives¹

Brown Algae (Phaeophyceae) from the Coast of Madagascar: preliminary Bioactivity Studies and Isolation of Natural Products

“…1 ), 24-ketocholesterol ( 5 ) (first preparation: Ref. [ 38 ], first isolation from an alga: Ref. [ 39 ]) (Fig.…”

Minor and trace sterols in marine invertebrates. 31. Isolation and structure elucidation of 23H-isocalysterol, a naturally occurring cyclopropene. Some comparative observations on the course of hydrogenolytic ring opening of steroidal cyclopropenes and cyclopropanes

“…The remarkably highfield shifted three-membered ring hydrogen (d X d X d) resonance signal (-0.126 ppm) with a larger 8-Hz and two smaller 4.5-Hz coupling constants can only be linked to the C-24 position. On the assumption that the smaller 4.5-Hz couplings are due to the vicinity of H-C( 23) and H-C (28), their positions on the threemembered ring have to be trans to H-C(24).13 Indeed, such a cyclopropane alkyl substitution pattern, in which the bulky isopropyl group is situated trans to the sterically less demanding methyl and «-alkyl groups, is also from the stereochemical viewpoint the most favorable one. This, in turn, leads to the two possible diastereoisomeric formulations (23/?,24/?,285)-3a and (235,245,28/?…”

“…Selected 'H NMR (360 MHz, CDCL) Chemical Shifts0 3H-CÜ8) 3H-C(21) 0.965 (6.6) 1.006 (6.0) 1.019 (6.9) 2H-C(23,28) 0.439 1H-C(25) 2.694 (6.8) 2.687 (6.4, 1.4) not assigned 6H-C(26,27) 1.105 (6.8), 1.097 (6.8) 1.151 (6.8), 1.099 (6.8) 0.930 (6.0), 0.929 (6.0) 1H-C (28) 1.330 (4.1) 3H-C (29) 0.999 (4.5) 1.994 (1.4) 0.990 (6.8) Main Mass Spectral Fragments6 410 ( 15) 410 ( 8) 412 ( 33) 395 ( 10) 395 (2) 397 ( 6) 392 ( 1) 314 ( 4) 394 ( 9) 377 ( 2) 300 ( 11) 379 ( 6) 367 ( 33) 271 ( 82) 356 ( 4) 349 ( 6) 253 ( 7) 328 ( 7) 300 ( 10) 231 (3) 314 ( 41) 271 ( 87) 213 ( 6) 300 ( 25) 253 (20) 96 ( 65) 273 ( 10) 231 ( 8) 95 (100) 271 ( 100) 213 (18) 255 ( 13) 110 ( 100) 231 ( 7) 213 (15) 0 Given as values, J values are given in parentheses in hertz. 6 Low-resolution data (MAT 711) obtained at 70 eV.…”

Increased flux of the plant sterols campesterol and sitosterol across a disrupted blood brain barrier

“…24-hydroxycholesterol (24-OHC) was described for the first time by two American chemists in the forties. They synthesized the compound starting from the bile acid 3βhydroxy-5cholestenoic acid through 24-ketocholesterol (Riegel and Kaye, 1944). In 1953, two Italian scientists published their discovery of a new sterol isolated from horse brain.…”