Preparation and chemical reactions of some polymer-supported steroids

Partial separation of enantiomeric 1,2-diols via ketal formation with a polymer-supported chiral ketone

“…8,9 The carboxylic acid groups 6 were converted into acid chloride residues 7, the latter reacted with 3b-hydroxy-5a-cholestan-7-one, † and the unreacted residues 7 capped with MeOH essentially as described before. 13 This gave polymer beads containing residues 1 with a loading (0.60 mmol g 21 ), similar to that reported before. 13 Ketal formation (step 1) was achieved by treating mixtures of enantiomeric diols in toluene at reflux temperature with PS ketone 1 in the presence of a catalytic amount of toluenep-sulfonic acid (PTSA).…”

“…13 This gave polymer beads containing residues 1 with a loading (0.60 mmol g 21 ), similar to that reported before. 13 Ketal formation (step 1) was achieved by treating mixtures of enantiomeric diols in toluene at reflux temperature with PS ketone 1 in the presence of a catalytic amount of toluenep-sulfonic acid (PTSA). The reaction was carried out for 56 h in an apparatus equipped with a Dean-Stark trap.…”

“…This may be due in part to some of the bound ketone being inaccessible due to steric crowding. 13 The diol recovered from the beads had a 42% ee of the (S,S)-diol 5a. With an equimolar amount of racemate (i.e.…”

A new method for the polymer-supported synthesis of cyclic oligoesters for potential applications in macrocyclic lactone synthesis and combinatorial chemistry

“…We have studied other reactions of this PS acid before. 27 Surprisingly in view of the results obtained with ricinoleic acid 13, treatment of the PS acid for 18 h with di-n-butyltin oxide under the standard conditions gave only a small soluble fraction which, by SEC, was a complex mixture which did not show the pattern expected for a mixture of COs. Use of the other catalyst systems tried initially with 11-hydroxyundecanoic acid 2 produced no soluble products other than, in the case of sodium methoxide, some methyl lithocholate. It had been hoped the reactions would have given some of the lithocholic acid COs 16 studied by Sanders' group.…”

“…The following procedure27 is typical of that used for the experiments summarised in Table1, entries 9 and 15.…”