I have become aware of a cashier's check for $150 US payable to the Syrian Embassy which was purchased at our bank in February. The check, endorsed, "Deposit to the credit of The Syrian Embassy Mughtarebeen" appears to have cleared through Riggs Bank NA in Maryland. Is this s transaction prohibited by OFAC?

Here's a link to BOL's OFAC Sanctions Matrix. You may want to start your investigation there; it is much easier to read than the information on the OFAC web site.