An improved synthesis of 1,2,3,4,6-Penta-O-Acetyl-5-Deoxy-5-C-[(R,S)-ethylphosphinyl]-α,β-d-glucopyranoses, and formation of 2,3,4,6-Tetra-O-acetyl-1,5-anhydro-5-deoxy-5-C-[(R)-Ethylphosphinyl]-d-glucitol