The Studies On The "On Water" Steroidal Epoxide Ring Opening Reactions

Sterols are an important kind of natural steroids which exist widely in the livingtissue. As an important kind of steols, polyhydroxysteroids and their derivatives arecommonly found in food products from plants and in marine invertebrates.Polyhydroxysteroids can be synthesized through dihydroxylation reactions whichstart with naturally occurring and abundant Δ5-steroids. The ring opening reaction isoften catalyzed by various acids in organic or aqueous organic media. The problemswith these procedures include non-quantitative yields for most of the systems, thenecessity of using organic solvents in the reactions and in the workup, and organicsolvents are volatile and pollute the environment.There have been no reports on ring opening reactions of very sparingly solublehigh-melting-point steroidal epoxides mediated by water that do not use organicsolvents. Dihydroxylated steroids have been prepared quantitatively by stirring amixture of a very sparingly soluble high-melting-point steroidal epoxide, aqueousH2SO4and polytetrafluoroethylene sand(PTFE); no organic solvents or phase transfercatalysts were used. Various functional groups such as ketones, esters, ethers, ketals,epoxides on D-rings and α, β-unsaturated ketones all survived these reactionconditions. We optimized the reaction conditions, and prepared a series of insolublehigh-melting-steroidal epoxy compounds (Mp:87-258℃, Solubility:2.2×102-5×106mol/L) as substrate for this reaction. The reaction has been repeated in the samemanner ten times, the reaction times and yields (>99%) remained almost the same forall cycles.The promoting effects of the sand for these “on water” reactions have beendemonstrated for the first time. This is a green, waste-free, mild and operationallysimple procedure. This methodology is useful for the synthesis ofpolyhydroxysteroids, reducing the cost of the products and protecting theenvironment.