We report on a major modification of the fundamental electronic band structure of AlAs when grown as a nanoscaled wurtzite crystal. Resonant Raman spectra of individual AlAs-GaAs core-shell nanowires display a resonance between 1.83 and 2.18 eV for the AlAs E(1)(TO) phonon mode. Our findings substantiate the lowest conduction band of wurtzite AlAs to comprise Γ(8) symmetry and a low effective mass in agreement with calculations reported recently. The electronic resonance falls below the X-, L-, and Γ- valleys known for AlAs in the zincblende phase. This result points towards a direct nature of wurtzite AlAs and is expected to apply more generally to semiconductors that in the bulk phase exhibit L-valleys at lower energies than the conduction band at the Γ-point.