Deleting Duplicate Rows

In my database, I have a table "tbl_c_extract" that consists of 4 columns that look the following. I'm looking at a daily batch of around 4000 records, of which 150 are likely to be duplicates.

Emp_No varchar(255), Proprietary_ID varchar(255), LeaveDateActual datetime
123456, E123456, 2014-09-27 00:00:00.000
213832, E123456, 2099-12-31 00:00:00.000
213836, E123456, 2014-01-31 00:00:00.000

In the example above, I need to remove 2 of the entries, leaving only the one that with the maximum leave date. In this case, those without a leave date have the 2099 entry.

Using CTE works exactly as I want it to, however SQL Server Agent doesn't seem to like the use of CTE..

Code:
WITH CTE (Proprietary_ID, LeaveDate, RN)
AS
(
SELECT Proprietary_ID, LeaveDate,
ROW_NUMBER() OVER(PARTITION BY Proprietary_ID ORDER BY Proprietary_ID, LeaveDate) AS RN
FROM tbl_c_extract
)
DELETE
FROM CTE
WHERE RN > 1