  For a commutative algebra which comes from a Zinbiel algebra the exponential
series can be written without denominators. When lifted to dendriform algebras
this new series satisfies a functional equation analogous to the
Baker-Campbell-Hausdorff formula. We make it explicit by showing that the
obstruction series is the sum of the brace products. In the multilinear case we
show that the role the Eulerian idempotent is played by the iterated pre-Lie
product.
