H2SO4-silica: an eco-friendly heterogeneous catalyst for the differential protection of myo-inositol hydroxyl groups

摘要: There is enormous interest in myo-inositol derivatives as they serve precursors for the synthesis of several biologically important phosphoinositols, natural products, catalyst, supramolecular architectures etc. However presence six secondary hydroxyl groups similar reactivity warrants protection inositol effective synthesis. Acid catalyzed orthoesters or ketals are most commonly used protecting strategy chemistry. Traditionally, homogeneous acid catalysts such para-toluene sulfonic (p-TSA) camphorsulfonic (CSA) these transformations. While reversible nature reactions necessitates catalyst removal, aqueous work up cannot be employed their removal products water soluble. We have circumvented this problem by using H2SO4-silica solid supported which can removed filtration, Treatment with trialkylorthoesters under normal conditions resulted esterification at least reactive group (C2-OH) giving exclusively corresponding 2-O-acyl-myo-inositol. By doing reaction a rotary evaporator reduced pressure formation orthoesters, wherein three protected simultaneously. could synthesize different 6–10 excellent yields method. Monoketaliziation one equivalent 1,1-dimethoxycyclohexane 2,2-dimethoxypropane simultaneous 1-OH and 2-OH 1,2-O-cyclohexylidene-myo-inositol (11) 1,2-O-isopropylidene-myo-inositol (12) yields. Also, diketalization gave diketals namely (±)-1,2:4,5-di-O-isopropylidene-myo-inositol (17), (±)-1,2:5,6-di-O-isopropylidene-myo-inositol (18) (±)-1,2:3,4-di-O-isopropylidene-myo-inositol (19) considerable Similarly when dimethoxycyclohexane was used, dicyclohexylidene (±)-1,2:4,5-di-O-cyclohexylidene-myo-inositol (20), (±)-1,2:5,6-di-O-cyclohexylidene-myo-inositol (21) (±)-1,2:3,4-di-O-cyclohexylidene-myo-inositol (22), were obtained good yield. 1,2:3,4-di-O-alkylidene-myo-inositols negligibly small other known methods, interestingly, our method give hence exploited synthetically. Thus cheap, eco-friendly, easy-to-make easy-to-handle we tune to make mono-protected, di-protected, tri-protected tetra-protected derivatives. These strategies applied economic various key intermediates purposes.