Alter materialized view - how to remove the start with ?

 Hello,

I own a set of views that I want altered.

They are all defined as follows:

CREATE materialized VIEW my_view01
build deferred
refresh force ON demand
start WITH to_date('12-07-2012 23:59:00', 'dd-mm-yyyy hh24:mi:ss') next to_date(TO_CHAR(SysDate,   'ddmmyyyy')||'23:59','ddmmyyyy hh24:mi')   
AS
SELECT ... FROM ...

I wish to alter to the following definition:

CREATE MATERIALIZED VIEW  my_view01
BUILD DEFERRED                                                 
REFRESH COMPLETE
ON DEMAND
AS
SELECT ... FROM ...

I was told to drop, but each views have grants, synonyms,  index that I do not want to recreate.

So my question how the alter materialized view for the new definition?