maintained under a nitrogen atmosphere was added 189 mg of oxalyl chloride in 5 ml of methylene chloride the reaction mixture was allowed to warm to room temperature for 60 minutes and was then washed successively with a dilute sodium bicarbonate solution water and a brine solution the separated organic phase was dried over sodium sulfate and concentrated to give the product as a white foam a employing the procedure of example 8a and starting with the appropriate thiomethyl penicillanate sulfones the following sulfoxides are prepared ______________________________________ str36 r r sub 1______________________________________h ch sub 3ch sub 3 ch sub 3h ch sub 3 ch sub 2 sub 2h ch sub 3 sub 3 ch ch sub 3 sub 2 chch sub 3 ch sub 3 sub 2 chch sub 3 ch sub 3 ch sub 2 sub 2 chh ch sub 3 ch sub 2 sub 2 ch ch sub 3 ch sub 2 str37 ch sub 3 str38 h str39 ch sub 3 str40 h str41 ch sub 3 c sub 6 h sub 5h c sub 6 h sub 5 ch sub 2______________________________________ b starting with indicated sulfinylmethyl penicillanate sulfones and halogenating agent and employing the procedure of example 8b the indicated halomethyl penicillanate sulfones are prepared ______________________________________ str42 str43 i halogen ii r r sub 1 ating agent r x______________________________________h ch sub 3 cl sub 2 h clh ch sub 3 i sub 2 h ich sub 3 ch sub 3 cocl sub 2 ch sub 3 clh ch sub 3 ch sub 2 sub 2 br sub 2 h brh ch sub 3 sub 3 c br sub.