Hint Rewrite split_first_PROP using not_conj_notation : norm1.

Lemma perm_derives:
forall Delta P Q R P' Q' R',
Permutation P P' ->
Permutation Q Q' ->
Permutation R R' ->
ENTAIL Delta, PROPx P (LOCALx Q (SEPx R)) |-- PROPx P' (LOCALx Q' (SEPx R')).