Disable button when a checkbox in a ng-repeat list is unchecked

I have a button that I need to disable if the there is no checked checkbox on my ng-repeat.

<button class="" data-toggle="modal" data-target="#rejectModal" contenteditable="false" id="delbutton" ng-model="delbutton" ng-disabled="!item.checked">

and my checkbox is like this

<input type="checkbox" name="select" value="checked" ng-model="item.checked"/>

How can I possibly do this?