*2,6-Anhydro-5-deoxy-7-O-acetyl-4-O-(tert-butyldimethylsilyl)-1,3:8,9:11,12-tri-O-isopropylidene-*β*-*d*manno-*d*-lyxo-dodeco-6-enitol (***4a***)*

A solution of **3** (300 mg, 0.537 mmol) and 4-dimethylaminopyridine (13 mg, 0.107 mmol) in triethylamine (7 mL) was treated with acetic anhydride (508 μL, 5.37 mmol) at 0 ◦C. After stirring for 12 h at ambient temperature until TLC indicated complete transformation of the starting material, the reaction mixture was diluted with ethyl acetate (20 mL). The organic phase was washed with 1 N hydrochloric acid (3 × 10 mL), sat. aq. NH4Cl-solution (1 × 10 mL) and brine (1 × 10 mL). The solution was dried with Na2SO4, the solvent was removed and the crude product was purified by column chromatography (petroleum ether/ethyl acetate 5:1) to afford **4a** (309 mg, 0.515 mmol, 96%) as a colorless crystalline solid. Rf = 0.82 (methylene chloride/ethyl acetate 5:1). [α]20D = +64.3 (c = 1.0, CHCl3). M.p. 52 ◦C (*n*-hexane). 1H-NMR (400 MHz, CDCl3): δ (ppm) = 4.99 (d, *J*5,4 = 2.2 Hz, 1H, H-5), 4.86 (dd, *J*9,8 = 5.6 Hz, *J*9,10 = 3.4 Hz, 1H, H-9), 4.69 (d, *J*8,9 = 5.6 Hz, 1H, H-8), 4.42 (ddd, *J* = 8.3 Hz, *J* = 5.9 Hz, *J* = 3.9 Hz, 1H, H-11), 4.35 (dd, *J*4,3 = 6.7 Hz, *J*4,5 = 2.1 Hz, 1H, H-4), 4.09–4.15 (m, 1H, H-12a), 3.99–4.07 (m, 2H, H-10, H-12b), 3.80–3.89 (m, 2H, H-1aH-1b), 3.61–3.73 (m, 2H, H-2, H-3), 2.01 (s, 3H, COC*H*3), 1.48, 1.47, 1.45, 1.37, 1.37, 1.33 (6s, 18H, C(C*H*3)2), 0.83 (s, 9H, SiC(C*H*3)3), 0.03, 0.03 (2s, 6H, SiC*H*3).13C-NMR (101 MHz, CDCl3): δ(ppm) = 168.3 (CO), 146.9 (C-6), 113.9, 109.4 (*C*(CH3)2), 107.4 (C-7), 104.8 (C-5), 99.3 (*C*(CH3)2), 86.4 (C-8), 81.2 (C-10), 79.6 (C-9), 73.0 (C-3), 72.8 (C-11), 70.2

(C-2), 68.2 (C-4), 67.1 (C-12), 61.7 (C-1), 28.9, 27.0, 25.8 (C(*C*H3)2), 25.6 (SiC(*C*H3)3), 25.1, 25.1 (C(*C*H3)2), 21.5 (CO*C*H3), 19.1 (C(*C*H3)2), 18.0 (Si*C*(CH3)3), –4.4, –4.9 (Si*C*H3). HRESIMS *m*/*z* 623.28604 (calcd for C29H48O11SiNa, 623.28581); anal. C 58.10, H 8.21, calcd for C29H48O11Si, C 57.98, H 8.05.
