How to get key from a listitem

//             // Create the ListBox                oSimpleListBox = new sap.ui.commons.ListBox({                allowMultiSelect: true,                id: "box1",                }).bindAggregation("items", "/jobs",                        new sap.ui.core.ListItem({                            text: "{job_desc}",                            key: "{job_number}"                        }));

                new sap.ui.commons.Button({                text: "Add",                    press: function() {                    var selectedItems = oSimpleListBox.getSelectedItems();                        alert(selectedItems);                        for (var i=0; i<selectedItems.length;i++) {                            var listItem = selectedItems[i];                            oSimpleListBox2.insertItem(listItem, 0);                        }                    }            }).placeAt("content"); 

I want to alert the key of "listItem" but i can't seem to, i just want to try and get the key(job_number) because I have a second listbox that updates with the ones i select from "box1" and is added correctly to the box which is bound to "/jobsp",but I can't get the second box's model to update with the new values it receives from the first box.

So wanted to try first getting the key.

Any ideas?

Thanks.