SQL & PL/SQL :: Double Quotes In Column Name Can Be Replaced With Alternate Character?

Any way to replace the Double Quotes used to enclose column names with an alternative character. This is the SQL I have now that Works!

select (case when CUST is null then "/BIC/Z_SUPPLNT" else NM1 end) CMPNTSUPSRCE
from TBL1, TBL2
where "/BIC/Z_MAJVEND"=CUST(+) and Material = '1ABCD456'
order by Material

But would like to do something along these lines below but keep getting error "ORA-00936: missing expression".

select (case when CUST is null then chr(34)||/BIC/Z_SUPPLNT||chr(34) else NM1 end) CMPNTSUPSRCE
from TBL1, TBL2
where chr(34)||/BIC/Z_MAJVEND||chr(34)=CUST(+) and Material = '1ABCD456'
order by Material