You haven't explained why you need to synchronise to this 2.048mhz clock. Why does the instruction execution need to be aligned with this clock?

If you need this clock to run an internal timer then I can understand the requirement - but the specs say the internal clock must be less than the cpu freq/12 (for a 8051/2 anyway).

One possibility is to phase lock the cpu clock to the 2.048mhz clock which is not too hard to implement with a few ics.

The only other suggestion I can think of is to use a cpu like the AVR where clocking at 2.048 mhz is not going to be such a performance hit.