Create Single purchase order from different sales order for single supplier

hi .
i have different sales orders.
example:
order1:
item1 - supplier 1
item2 - supplier 2
item3 - supplier 1

order 2:
item1- supplier 1
item4- supplier 1
item5 - supllier 2

now i need two purchase order like this :
purchase order1: for supplier1
item1 in order 1+ item1 in order 2
item3 in order 1
item4 in order2
purchase order2: for supplier 2
item2 in order 1
item5 in order 2

how can i do that
thanks