methods of breaking disulphide bonds

[Mrinal Singha]

Respected Sir/Madam

     I am trying to form methyl ester of 4-Mercapto benzoic acid by using
thionyl chloride and then adding methanol at room temparature. Although
ester is formed but it is also forming disulfide. I want to cleave disulfide
bond without cleavage of ester. Please tell me some suitable methods for
this.


       Thank You
   Mrinal singha
   Student of Master of Science( Medicinal Chemistry)
   National Institute of Pharmaceutical Education and Research(NIPER)
   Punjab,India