ISE Design Suite 11.2 supports and allows users to target Virtex-6 FPGA Lower Power devices.
At this time, there is limited IP support and no third-party synthesis tool support for these devices.
For details on which IP are supported for the 11.2 release of ISE Design Suite, see the
IP Release Notes Guide at:
http://www.xilinx.com/support/documentation/ip_documentation/xtp025.pdf If Virtex-6 Lower Power device support is required, as a work-around, you can target Virtex-6 -1 devices in the synthesis tool and CORE Generator first, then re-target to Lower Power (-1L) devices during design simulation, implementation, and Power Estimator/Analyzer.