  We consider a class of exponentials in the Weyl-Heisenberg algebra with
exponents of type at most linear in coordinates and arbitrary functions of
momenta. They are expressed in terms of normal ordering where coordinates stand
to the left from momenta. Exponents appearing in normal ordered form satisfy
differential equations with boundary conditions that could be solved
perturbatively order by order. Two propositions are presented for the
Weyl-Heisenberg algebra in 2 dimensions and their generalizations in higher
dimensions. These results can be applied to arbitrary noncommutative spaces for
construction of star products, coproducts of momenta and twist operators. They
can also be related to the BCH formula.
