4-5 point pincers
The black pincers at , or a, are sufficiently rare in high-level go that one can question whether they are joseki. Perhaps to play the 4-5 point is to resign oneself to not playing a pincer, in normal circumstances. 8dan game on IGS 20091207 where white played this in 2 corners
In case White plays the 5-3 approach here, there is no local reason why Black shouldn't play at a (transposing to a normal 3-3 point variation).
Considering though that is probably played in relation to the position across the top side, Black tries other replies: the press at b, the taisha at c, the pincers d and e are all known from pro play.