“…If, R =ethoxycarbonylmethyl A yellow oil; IR (neat) 1790, 1750, 1640 cm'. lH NMR (CDCl;) 8 1.24 (3R, t, J :::7 Hz, OCH 2 CH 3 ) , 1.33 (3H, t, J::: 7 Hz, OCH£H3) , 2.06 (3H, S, OqO)CH 3 ) ,3.77 (2H, S, (O)CCH2C(O», 4.16 (2H, q, J =7 Hz, OCHzCH3), 4.34 (2H, q, J '" 7 Hz, OCH2C H 3 ) . MS (12 eV) m/z 231 (M+ • CHz=C=O, 20), 185 (l00), 157 (35).…”