5 4 hz 1h 6 79 d j 7 9 hz 1h 4 90 4 70 m 2h 4 44 d j 3 4 hz 1h 4 32 dd j 4 2 1 6 hz 1h 4 24 d j 4 3 hz 1h 3 86 s 3h 3 81 s 3h 3 44 s 3h 3 43 s 3h 3 15 3 00 m 2h 2 65 2 40 m 3h 1 30 1 15 m 18h general procedure e starting from 131 reaction time 24 h and chromatography on silica gel ch 2 cl 2 meoh from 50 1 to 30 1 to afford 129 as a yellow solid 53 mg 79 1 h nmr 300 mhz cdcl 3 u03b4 9 21 d j 7 6 hz 1h 7 40 7 05 m 6h 6 78 d j 9 1 hz 1h 5 15 5 05 m 3h 4 65 4 50 m 3h 3 86 s 3h 3 81 s 3h 3 48 s 3h 3 42 s 3h 2 50 2 30 m 3h 1 49 s 18h 1 46 s 9h 1 25 0 95 m 18h 13 c nmr 75 mhz cdcl 3 u03b4 170 2 3c 155 9 155 7 154 9 153 1 152 2 147 6 145 4 145 3 141 7 139 9 139 4 138 7 134.