Synthesis of the four stereoisomers of 22,23-dimethylcholesterol was written by Gebreyesus, Tarekegn;Djerassi, Carl. And the article was included in Journal of Organic Chemistry in 1985.SDS of cas: 28322-40-9 This article mentions the following:
The 4 diastereoisomers of 22,23-dimethylcholesterol I were prepared from cyclodinorcholanal II and characterized by NMR spectroscopy and HPLC. Thus, Grignard reaction of Me iodide with II and subsequent Jones oxidation gave cyclonorcholenone III (Z = O), which underwent Wittig condensation with Me2CHCH2CH2P+Ph3 Br– to give III (Z = Me2CHCH2CH:). Hydroboration-oxidation of the latter and then Jones oxidation gave methylcyclocholestanones IV (Z1 = O), which underwent Wittig reaction with MeP+Ph3 Br– to give IV (Z1 = CH2🙂 (V). Hydrogenation of (22R)-V and subsequent hydrolysis gave (22S,23R)- and (22S,23S)-I. Hydroboration-oxidation of (22S)-V gave diastereoisomeric IV (Z1 = H, HOCH2), which underwent successive mesylation, LiAlH4 reduction, and hydrolysis to give (22R,23R)- and (22R,23S)-I. In the experiment, the researchers used many compounds, for example, Isopentyltriphenylphosphonium bromide (cas: 28322-40-9SDS of cas: 28322-40-9).
Isopentyltriphenylphosphonium bromide (cas: 28322-40-9) belongs to organobromine compounds. Bromine is more electronegative than carbon (2.9 vs 2.5). Consequently, the carbon in a carbon–bromine bond is electrophilic, i.e. alkyl bromides are alkylating agents. One prominent application of synthetic organobromine compounds is the use of polybrominated diphenyl ethers as fire-retardants, and in fact fire-retardant manufacture is currently the major industrial use of the element bromine.SDS of cas: 28322-40-9
Referemce:
Bromide – Wikipedia,
bromide – Wiktionary