S-O Acetyl rearrangement in 6-thio-D-glucose derivatives

Velimir Popsavin, Mirjana Popsavin, Dušan Miljković

Abstract


Solvolytic reaction of 1,2-O-isopropylidene-3,6-di-O-(p-toluene­sulphonyl)-α-d-glucofuranose (2), as well as 6-chloro-6-deoxy-1,2-O-iso­propylidene-α-d-glucofuranose (3) in presence of potassium thioacetate unexpectedly gave 6-S-acetyl-5-O-acetyl derivative 5 as the main reaction product. A possible mechanism of these transformations was postulated whereby the main role was ascribed to a neighbouring group participation process, involving hydrogen thio-ortoester formation as an intermediate. Regiospecific monosupstitution of 6-tosyloxy group in compound 2 was successfully achieved with potassium thioacetate, in presence of 1,2-benzo[15,5]crown ether as a catalyst. The corresponding 6-S-acetyl derivative 7 was obtained representing a possible intermediate in the mentioned solvolytic reactions. Compound 7 was shown to be very reactive, since it fully transforms into the corresponding mercaptan 8 in the presence of silica gel. This transformation takes place via the same thio-ortoester 7a as in the mentioned solvolytic reactions of furanoses 2 and 3. The synthesized compounds are key intermediates in the planned synthesis of selected natural products and their analogues.

Keywords


solvolysis; tosyloxy leaving group; thiosugars; neighbouring group participation; thio-ortoester

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DOI: https://doi.org/10.2298/JSC180811075P

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