  We report on the first measurement of cross sections for exclusive deeply
virtual pion electroproduction off the proton, $e p \to e^\prime n \pi^+$,
above the resonance region at backward pion center-of-mass angles. The
$\varphi^*_{\pi}$-dependent cross sections were measured, from which we
extracted three combinations of structure functions of the proton. Our results
are compatible with calculations based on nucleon-to-pion transition
distribution amplitudes (TDAs) and shed new light on nucleon structure.
