c 1 g the starting material was consumed within 30 min the mixture was filtered through a pad of diatomaceous earth and concentrated the residue was dissolved in methylene chloride and washed with water and brine the organic solution was dried over na 2 so4 filtered and concentrated the title compound 4 52 g was isolated as a light yellow solid in 97 yield as a 1 1 3 isomeric mixture data recorded from a 1 1 3 isomeric mixture tlc r f 0 83 acetonitrile ir chcl 3 3010 1670 1628 1332 1174 1041 922 cm 1 1 h nmr cdcl 3 300 mhz d 8 18 d 2h j 9 2 7 39 d 2h j 11 4 7 38 d 2h j 10 6 91 s 1h 6 89 s 1h 6 62 d 2h j 8 5 6 61 d 2h j 8 1 6 57 s 1h 6 56 s 1h 6 06 m 4h 4 71 sext 2h j 7 3 9 br s 4h 2 86 s 3h 2 78 s 3h 2 74 2 49 m 4h 1 29 d 3h j 10 8 1 25 d 3h 10 8 mass spectrum m z fd m 433 uv max ethanol 326 nm u03b520767 231 17587 205 42765 to a solution of the example 19 intermediate 0 51 g in 6 ml thf was added a single portion of lithium tert butoxide 0 17.