Consider the example:R(A,B,C,D,E,F)
ABC-->DEF
D-->A
This is in 3NF(key is ABC,there is no Transitive or partial dependency)
But,here there exists non key to key FD(that is LHS is not super key[D-->A])
Also here we have one compound candidate key -ABC
But it is not in BCNF
So the statement{Relation R which satisfies 3nf and atmost one compound candidate key is also bcnf} should be false