Jena support for Named Graphs syntax

Hello,

I was trying to load a toy example on named graphs approach in Jena and 
test it using some queries.

While doing this, the syntax below didn't work for me:

|ex:G rdfg:isGraph { ex:B ex:prop2 ex:C } |

But instead this syntax using GraphLiteral works.

ex:G rdfg:isGraph "ex:B ex:prop2 ex:C"^^rdfl:GraphLiteral

Why the curly brackets are not supported? Is there a particular 
configuration or something I do to be used in Jena for named graphs.

Thank you