Synthesis of L-scyllo-inositol 1,2,4-trisphosphate, scyllo-inositol 1,2,4,5-tetrakisphosphate and phosphorothioate and DL-2-deoxy-2-fluoro-myo-inositol 1,4,5-trisphosphate: optical resolution of DL-1-O-allyl-3,6-di-O-benzyl-4,5-O-isopropylidene-scyllo-inositol

Routes for the synthesis of scyllo-inositol tris-and tetrakis-phosphates and 2-deoxy-2-fluoro-myo-inositol 1,4,5-trisphosphate from myo-inositol have been devised. For DL-scyllo-inositol 1,2,4-trisphosphate, DL-1-O-allyl 1–3,6-di-O-benzyl-4,5-O-isopropylidene-scyllo-inositol was prepared from the triflate of DL-1-O-allyl-3,6-di-O-benzyl-4–5-O-isopropylidene-myo-inositol by inversion at C-2. Removal of the isopropylidene group and phosphorylation gave the protected trisphosphate. Deblocking with sodium in liquid ammonia afforded racemic scyllo-inositol 1,2,4-trisphosphate. DL-1-O-Allyl-3,6-di-O-benzyl-4,5-O-isopropylidene-scyllo-inositol was resolved into its enantiomers by means of the crystalline 2-O-camphanate ester. The structure of one diastereoisomer, 1D-O-allyl-3,6-di-O-benzyl-2-O-[(–)-camphanate]-4,5–0-isopropylidene-scyllo-inositol was determined by single-crystal X-ray crystallography. 1D-(+)-1-O-Allyl-3,6-di-O-benzyl-4,5-O-isopropylidene-scyllo-inositol was used to prepare 1L(–)-scyllo-inositol 1,2,4-trisphosphate in a fashion analogous to the racemic modification. DL-1-O-Allyl-3,6-di-O-benzyl-scyllo-inositol was isomerised to the (Z)-prop-1-enyl derivative. The propenyl group was then removed to give the meso-1,4-di-O-benzyscyllo-inositol. Phosphitylation followed by oxidation or sulfoxidation gave the fully protected tetrakis-phosphate or -phosphorothioate, respectively. After deblocking and purification, scyllo-inositol 1,2,4,5-tetrakisphosphate and scyllo inositol 1,2,4,5-tetrakisphosphorothioate were obtained. DL-1-O-Allyl-3,6-di-O-benzyl-4,5-O-isopropylidene-scyllo-inositol was isomerised to the 1-O-[(Z)-prop-1-enyl] derivative which was converted into the 2-O-triflate. Displacement of the triflate using tetrabutylammonium fluoride proceeded with inversion of configuration to give DL-3,6-di-O-beflzyl-2-deoxy-2-fluoro-4,5-O-isopropylidene-1-O-([(Z)-prop-1-eny]-myo-inositol. Removal of propenyl and isopropylidene groups afforded DL-3,6-di-O-benzyl-2-deoxy-2-fluoro-myo-inositol, which was phosphitylated and the product oxidised to give the fully protected 2-fluoro trisphosphate. Deprotection furnished DL-2-deoxy-2-fluoro-myo-inositol 1,4,5-trisphosphate. These compounds will be useful probes for investigation of the polyphosphoinositide pathway of cellular signalling.