The present invention provides prodrugs of analogs of the anti-tumor antibiotic CC-1065 having a cleavable protective group containing a sulfonic acid containing phenyl carbamate, in which the protecting group confers enhanced water solubility upon the prodrug, and in which the prodrug also has a moiety, such as a sulfide or a disulfide, that can conjugate to a cell binding reagent such as an antibody, and for the therapeutic use of such prodrug and conjugates, and for processes for preparing such prodrugs and conjugates.