hz 21 h 3 0 521 3h s 18 h 3 0 060 0 046 0 029 and 0 006 each 3h each s 4 u00d7 s 1 u2014 ch 3 ms ei m z 628 3 m 613 1 m u2212 me 571 3 m u2212 t bu 496 63 m u2212 t bume 2 sioh 383 4 m u2212 t bume 2 sioh u2014 c 8 h 17 366 21 234 20 129 41 75 100 exact mass calculated for c 39 h 72 o 2 si 2 628 5071 found 628 5068 protected vitamin 8 10 mg 16 u03bcmol was dissolved in anhydrous thf 3 ml and a solution of tetrabutylammonium fluoride 1 m in thf 160 u03bcl 160 u03bcmol was added followed by freshly activated molecular sieves 4a 300mg the mixture was stirred under argon at room temperature for 2 h then diluted with 2 ml of hexane ethyl acetate 6 4 and applied on a waters silica sep pak cartridge 2 g elution with the same solvent system gave the crude product i that was further purified by hplc 10 u00d7 250 mm zorbax silica column 4 ml min using hexane 2 propanol 9 1 solvent system analytically pure 2 methylene 19 norvitamin i 3 3 mg 52 yield was collected at r v 32 ml as a colorless oil uv in etoh u03bb max 261 5 251 5 243 5 nm 1 h nmr 500 mhz cdcl 3 tms u03b46 36 and 5 88 1h and 1h each d j 14 3 hz 6 and 7 h 5 11 and 5 09 each 1h each s ch 2 4 47 2h m 1 u03b2 and 30 h 2 85 1h dd j 13 4 4 6 hz 100 h 2 81.