  In this paper, we show that the quantum Stokes matrices, of certain
meromorphic linear system of ordinary differential equations, give rise to a
family of Drinfeld isomorphisms from quantum groups to the undeformed universal
enveloping algebra of ${\frak {gl}}(n)$. In particular, we compute explicitly
the Drinfeld isomorphisms corresponding to caterpillar points on the parameter
space. Our computation unveils a relation between the asymptotics of confluent
hypergeometric functions and the Gelfand-Zeitlin subalgebras. As by products,
we show that the Drinfeld isomorphisms at caterpillar points coincide with the
Appel-Gautam isomorphisms. Then by going to the semiclassical limit, we place
the results in this paper into the context of Poisson geometry. As an
application, we prove the conjecture of Appel and Gautam, i.e., their
isomorphisms are canonical quantization of the Alekseev-Meinrenken
diffeomorphisms arising from the linearization problem in Poisson geometry.
