MOLECULAR STRUCTURE AND VIBRATIONAL AND CHEMICAL SHIFT ASSIGNMENTS OF (4R)-5-ENO-4,7-EPIDIOXY-3,7-O-METHYL-1,2-O-(S)TRICHLOROETHYLIDENE-5,6,8-TRIDEOXY-D-D-THREO-1,4-FURANO- 4,7-DIULO-OCTOSE BY DFT AND AB INITIO HF CALCULATIONS