[rayiner]

I haven't found one. Lenovo has no quad core 15" and the XPS 15 has pretty bad battery life in the 4K model.

[jpalomaki]

Lenovo has P50. Quad core, 15", 64GB max, but not slim.

The only other viable Lenovo quad core is T460p. But that's 14"and probably screen is quite bad compared to Macbook. Max memory is 32GB.

HP has ZBook 15, which might be worth checking.