Solution : https://service.sap.com/sap/support/notes/181268 (SAP Service marketplace login required)
Key words : 
create multiple assigned purchase orders, assign shopping basket items, additional key words bbppu01, multiple account assignment, -business procurement plugin, sap business-, -business procurement, e-business, cost objects, backend system
Related Notes : 
       
| 503196 | Enterprise Buyer 3.5 Installation: Composite Note | 
| 409263 | Enterprise Buyer 3.0 Installation: Composite Note | 
| 360142 | Enterprise Buyer 2.0 Installation: Composite Note | 
| 303515 | SAP Bus.-to-Bus. 2.0B Installation: Composite Note | 
| 185164 | SAP Bus.-to-Bus. 2.0A Installation: Composite Note |