How to disable the checkbox click to make atleast one check box to be selected - angularjs-directive

Question

I am new in angular2 ,I want disable the check box unchecking if there is only one check box is checked .my html page is look like this
<div class="Columns-list-box pull-right">
<a class="Columns-list" role="button" data-toggle="collapse" href="#collapseExample-check" aria-expanded="false" aria-controls="collapseExample-check">
Columns <span class="caret"></span>
</a>
<div class="collapse Columns-list-items" id="collapseExample-check">
<ul class="sub-mnu" id="menu-check" aria-labelledby="drop5">
<li >
<label><input #idDiv type="checkbox" [(ngModel)]= "productIdValue" (change)="mapItems($event)" name="id" [checked]="defaultCheck" >Id</label>
</li>
<li>
<label><input #skuDiv type="checkbox" (change)="mapItems($event)" [(ngModel)]= "skuDivValue" checked >SKU</label>
</li>
<li>
<label><input #shortnameDiv type="checkbox" (change)="mapItems($event)" [(ngModel)]= "ShortNameValue" checked >Shortname</label>
</li>
<li>
<label><input #identifierDiv type="checkbox" (change)="mapItems($event)" [(ngModel)]="identifierDivValue" checked >Identifier</label>
</li>
<li>
<label><input #identifierTypeDiv type="checkbox" (change)="mapItems($event)" [(ngModel)]="identifierTypeValue" checked>Identifier Type</label>
</li>
</ul>
</div>
</div>
mapItems() {
if (this.productIdValue || this.skuDivValue || this.ShortNameValue || this.identifierDivValue || this.identifierTypeValue) {
}
else {
this.defaultCheck = true;
}
}