some XPath please ?

Hi List.
Suppose I get a (simple) XML
<xml>
<tag1>
 <tag2>
  <tag3/>
  <tag3/>
 </tag2>
 <tag2>
  <tag3/>
  <tag3/>
  <tag3/>
 </tag2>
</tag1>
<tag2>
 <tag3/>
 <tag3/>
</tag2>
<tag2>
 <tag3/>
 <tag3/>
 <tag3/>
</tag2>
</xml>

What if I want to select all tag2 elements that did not have a tag1
above ?
I have tried

"//tag2[parent::node!=3D'tag1']/*"

But it gets all ...

And

"//tag2[parent::node!=3Dtag1]/*"

Gets nothing

(and I would prefer not using the higher level nodes like /xml/tag2
against /xml/tag1/tag2)

Thanks in advance !
Regards,
Fabien