A　new　chiral　Bronsted　acid,　generated　in　situ　from　a　chiral　phosphoric　acid　boron　(CPAB)　complex　and　water,　was　successfully　applied　to　asymmetric　indole　reduction.　This　＂designer　acid　catalyst＂,　which　is　more　acidic　than　TsOH　as　suggested　by　DFT　calculations,　allows　the　unprecedented　direct　asymmetric　reduction　of　C2-aryl-substituted　N-unprotected　indoles　and　features　good　to　excellent　enantioselectivities　with　broad　functional　group　tolerance.　DFT　calculations　and　mechanistic　experiments　indicates　that　this　reaction　undergoes　C3-protonation　and　hydride-transfer　processes.　Besides,　bulky　C2-alkyl-substituted　N-unprotected　indoles　are　also　suitable　for　this　system.