A process suitable for industrially preparing 2,3-trans-1,4-bridged cyclohexane sulfonamide derivatives, especially useful as an intermediate for the synthesis of a trans bicyclo[2,2,1] heptane carboxylic acid derivative, a clinically important thromboxane A.sub.2 antagonist, comprising: allowing to react corresponding a cis/trans mixture of sulfonamide derivatives with an anionoid or water-soluble carbonyl reagent at pH3-7 so that the trans isomer may form a water-soluble adduct with the anionoid or carbonyl reagent, separating the resulting adduct dissolved in an aqueous layer, and recovering the trans isomer by treating the adduct with a base or an acid. Also provided is an alkali metal hydrogen sulfite adduct of 2,3-trans 1,4-bridged cyclohexane sulfonamide derivative.