Establishment of the Structure of Pinpollitol by Total Synthesis of the Proposed Putative Structures

Proposed structures of pinpollitol, namely 1,4-di-O-methyl-chiro-inositol and 1,3-di-O-methyl-chiro-inositol, have been synthesized from myoinositol. Racemic 1,4-di-O-methyl-chiro-inositol has been synthesized from the readily available 1,2:4,5-di-O-isopropylidene-myo-inositol, in five steps while DL-1,3-di-O-methyl-chiro-inositol from myo-inositol 1,3,5-ortho formate in nine steps. A comparison of the reported NMR data of pinpollitol with those of synthetic dimethyl ethers revealed that pinpollitol is D-1,4-diO-methyl-chiro-inositol. Thus we have not only confirmed the structure of pinpollitol unambiguously but also achieved a rapid total synthesis of it from a cheaply available starting material, myo-inositol, in just six steps.