When can I apply for Singapore PR after upgrading to E Pass?

I had been working for 5 years in Singapore with work permit and recently just upgraded to e pass so could I apply for Singapore PR but my E pass just been issued?

Check with ICA, but I think you can apply either immediately or after 6 months of EP.
Whether you will become PR is yet another question - your chances are much higher after 3 years working on EP-