Synthesis of 3 from 11. A solution of 11 (250 mg, 1.45 mmol) in 80% aqueous AcOH (25 mL) was refluxed for 0.5 h. The solvent was evaporated in vacuo to afford a yellow solid. Pure product (3) was obtained in 82% yield by recrystallization of the crude yellow solid (EhO/pentane, 1:4), mp 124-127 "C (lit.3 mp 124-125 "C).Synthesis of 1,2:3,4-Bis-0 -( l-methylethylidene)-5bromo-5-deoxyxylitol. Into a solution of 1,2:3,4-bis-0-(1-methylethy1idene)-5-tosylxylito18 (38.5 g, 0.1 mol) in 250 mL of DMF was added lithium bromide (21.0 g, 0.2 mol). After the solution was stirred at 90 "C for 2 h, it was cooled to room temperature, poured into icewater, and extracted with ether. The extract was washed with brine, dried over MgS04, and filtered, and the filtrate was evaporated. The residue was distilled under reduced pressure to give 1,2:3,4-bis-O-(l-methylethylidene)-5bromo-5-deoxyxylito1(26.0 g, 0.088 mol) in 88% yield bp 97.5-102 "C (2-3 mm); IR (neat) cm-'; 'H NMR (CC14) 6 1.33 (br s, 12 H), 3.40 (d, J = 5 Hz, 2 H), 3.7-4.4 (m, 5 H). Anal. Calcd for CllH19Br04: C, 44.76; H, 6.49; Br, 27.07. Found: C, 44.91; H, 6.58; Br, 27.41. Synthesis of 1,23,4-Bis-0 -( l-methylethylidene)-5-deoxy-4,5-didehydroxylitol (15). Into a distillation flask were charged 1,2:3,4-bis-0-( l-methylethylidene)-5-bromo-5-deoxyxylitol(23.6 g, 0.80 mol) and pulverized KOH (54 g, 0.96 mol), and the mixture was heated under reduced pressure to distill crude vinyl ether. Fractional distillation gave 15: bp 101-105 "C (15 mm); yield 14.5-15.8 g (85-92%) ; IR (neat) 2990,2940,2880,1680,1380,1220, 1150, 1060 cm-'; 'H NMR (CC14) 6 1.25 (8, 3 H), 1.33 (s,6 H), 1.43 (s, 3 H), 3.50-4.33 (m, 5 H), 4.53 (m, 1 H); mass spectrum, m / e 214. 0-( l-methylethylidene)-5-bromo-5-deoxyxylitol, 87597-70-4.
