Laravel 5: Native SQL to Query Builder

I am trying to join 2 tables on Laravel 5 and have to use Query Builder. I have already got the sql for it but i am not able to convert it to Query Builder syntax. SQL is below

SELECT v.id, r.full_name, b.full_name, s.full_name
FROM vehicles v
LEFT JOIN clients r ON v.representive_client_id = r.id
LEFT JOIN clients b ON v.buyer_client_id = b.id
LEFT JOIN clients s ON v.seller_client_id = s.id

and what i tried is

    $query_result = DB::table('vehicles')   
                    ->selectRaw($query)
                    ->leftJoin('clients', 'vehicles.representive_client_id', '=', 'clients.id')
                    ->leftJoin('clients', 'vehicles.buyer_client_id ', '=', 'clients.id')
                    ->leftJoin('clients', 'vehicles.seller_client_id ', '=', 'clients.id')
                    ->paginate(30);

The problem is i dont know how to use AS caluse for Query Builder as i need to retrive 3 different types of full_name columns from vehicles table.Anybody can help me about how to write it in a proper Query Builder syntax ?. Any help would be appreciated.

via Chebli Mohamed