No, his previous salats will be deemed void and he ought to compensate for those salats which were executed whilst in a stae of janabah. Being purified from states of hadath (state of impurity which is removed, in this case, by means of ghusl) is a prerequisite vis-à-vis the salat’s validity. Hence, assuming one abandons such a prerequisite, his salat will be void – irrespective of whether (i) he was aware or ignorant (of the ruling) and (ii) he carried it out on purpose or out of negligence.