Abstract The reaction of ricinolic acid methyl ester with diazomethane in the presence of Co (BF 4) 2· 6H 2 Oresults in selective methylation of the hydroxy group. Methyl (2 Z'12 R)-12- acetoxy-9-octadecenoate reactswith diazomethane in the presence of Pd (acac) 2, leading to formation of a mixture of cis-cyclopropanated (9 S'10 S'12 R)-,(9 R'10 R'12 R)- diastereoisomers at a ratio of 3: 2 (overall yield 73%). Under similarconditions methyl (9 Z) ...