Steroids cclix11Part CCLVIII. J. Romo, L. Rodriguez-Hahn, P. Joseph-Nathan, M. Martínez and P. Crabbe. Bull. Soc.Chim. France (submitted for publication).. The synthesis of 5β,19 and 6β,19-cyclo steroids

Total Synthesis of Linckosides A and B, the Representative Starfish Polyhydroxysteroid Glycosides with Neuritogenic Activities

“…As expected, glycosylation of 25 at 29-OH with o -hexynylbenzoate donor 6 proceeded smoothly under the catalysis of PPh 3 AuNTf 2 (0.2 equiv); subsequent removal of the 3- O -MOM group with HCl in THF/H 2 O facilitated the purification of the product to provide α- l -arabinofuranoside 26 in a good 72% yield (Scheme ). Oxidation of the 3-OH (in triol 26 ) with pyridinium chlorochromate in CH 2 Cl 2 followed by treatment with HCl in dioxane led to the corresponding Δ 4,5 ,3-one derivative, which was subjected to Luche reduction to afford Δ 4,5 ,3β-ol 27 (64%) . It was noted that direct dehydration of the 5α-OH in 17 after acetylation of 6β-OH was not successful.…”

Steroid rearrangements. Reactions of a 16,17.alpha.-epoxypregnan-20-one with hydrogen fluoride. Thermal dehydrofluorinations

“…Finally, attention is called to the 17a-fluoropregnanes 12 to 14 and 16 to 19. The converging vector rule does not apply (18-methyl and 21-methyl hydrogens separated from the fluorine by 4 bonds). A small 18-H-17a-F coupling was observed in one case (18, Jfh = 1.3 Hz).…”