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0 °C

Isomannide (40) (10 g, 68.49 mmol) and p-toluenesulphonyl chloride (6.53 g, 34.25 mmol) were dissolved in a mixture of carbon tetrachloride (50 mL), dichloromethane (5 mL) and water (40 mL). The flask was cooled to 0° C. and a solution of potassium hydroxide (1.92 g, 34.25 mmol) in water (5 mL) added dropwise over 30 minutes with stirring. The resulting biphasic mixture was stirred at 0° C. for 7 hours. Then off-white precipitate was collected by filtration in vacuo then partitioned between dichloromethane (30 mL) and water (10 mL). The organic phase was washed with brine (2×10 mL) then dried (Na2SO4), filtered and reduced in vacuo to leave a colourless solid. Recrystallisation from carbon tetrachloride gave monotosylate (50) as colourless granules (3.92 g, 38%). TLC (Rf=0.11, EtOAc:heptane 1:1); analytical HPLC main peak, Rt=10.692 min; HPLC-MS 318.2, 323.1 [M+Na]+, 623.2 [2M+Na]+; [α]D18+72.2° (c=5.4, CHCl3); δH (500 MHz, CDCl3) 2.44 (3H, s, CH3), 3.54 (1H, dd, J=9.31 and 7.23 Hz, OCH2CHOH), 3.78 (1H, dd, J=9.18 and 7.59 Hz, OCH2CHOTs), 3.95 (1H, dd, J=9.36 and 6.45 Hz, OCH2CHOH), 4.01 (1H, dd, J=9.33 and 6.64 Hz, OCH2CHOTs), 4.26 (1H, m, CHOH), 4.42 and 4.48 (each 1H, brt, J=5.03 and 5.00 Hz respectively, CHCHCHOH and CHCHCHOTs), 4.90 (1H, dd, J=12.15 and 6.84 Hz, CHOTs), 7.37 (2H, d, J=8.13 Hz, aromatic CH3CCH), 7.82 (2H, d, J=8.20 Hz, aromatic OSO2CCH); δC (125 MHz, CDCl3) 21.69 (CH3), 70.03 (CH2CHOTs), 72.29 (CHOTs), 74.02 (CH2CHOH), 80.00 (CH2CHOH), 81.36 (CHCHOTs), 81.76 (CHCHOH), 128.00 and 129.89 (aromatic CH), 133.04 (CHOSO2C quaternary), 145.26 (CH3C quaternary).

1. stirringThe resulting biphasic mixture was stirred at 0° C. for 7 hours
2. filtrationThen off-white precipitate was collected by filtration in vacuo
3. customthen partitioned between dichloromethane (30 mL) and water (10 mL)
4. washThe organic phase was washed with brine (2×10 mL)
5. dry with materialthen dried (Na2SO4)
6. filtrationfiltered
7. customto leave a colourless solid
8. customRecrystallisation from carbon tetrachloride