Compared to other literature reports, this E value of 44 is not as high as that reported for other HHDHs, e.g. HheC or HheA2 N178A, that ─ unlike HheG ─ display β-regioselectivity in the ring opening of 3. In contrast to most other HHDHs with α-regioselectivity, however, all HheG variants preferentially convert (R)-styrene oxide yielding azidoalcohol (S)-4 (Scheme S1).