saturated aqueous sodium bicarbonate the organic layer was then dried over anhydrous sodium sulfate and concentrated in vacuo to yield a gum which was purified by silica gel flash column chromatography to give 10 61 g of compound 1 as a white foam 1 h nmr d 6 dmso 400 mhz u03b4 8 92 d 1h j 9 2 7 91 d 2h j 8 5 7 62 d 2h j 8 5 6 48 s 1h 5 52 dd 1h j 8 5 3 2 4 7 u2013 4 32 m 3h 3 19 s 3h 1 31 s 9h 1 29 s 9h esms negative mode relative abundance shown in parentheses m z208 80 100 491 66 90 493 54 70 547 68 30 549 51 25 m hplc t r 11 2 min purity 96 6 column ace 5 c18 4 6 u00d7 150 mm mobile phase 0 1 aq h 3 po 4 ch 3 cn gradient to a solution of compound 1 12 75 g 23 2 mmol in anhydrous dichloromethane 150 ml under nitrogen was added trifluoroacetic acid 15 ml and the solution was stirred at ambient temperature for 2 hours the solution was then concentrated in vacuo to yield a gum which upon trituration with diethyl ether gave 9 97 g of compound 2 as a white solid 1 h nmr d 6 dmso 400 mhz u03b4 8 81 d 1h j 9 0 7 87 d 2h j 8 4 7 63 d 2h j 8 4 6 43 s 1h 5 58 dd 1h j 9 6 2 0 4 80 u2013 4.