  We present a measurement of the time-dependent CP-violating asymmetries in
decays of neutral B mesons to the final states D*-+ pi+-, using approximately
232 million BBbar events recorded by the BABAR experiment at the PEP2 e+e-
storage ring. Events containing these decays are selected with a partial
reconstruction technique, in which only the high-momentum pi+- from the B decay
and the low-momentum pi-+ from the D*-+ decay are used. % We measure the
parameters related to 2beta+gamma to be a_D*pi=-0.034 +- 0.014 +- 0.009 and
c_l_D*pi = -0.019 +- 0.022 +- 0.013. With some theoretical assumptions, we
interpret our results in term of the lower limits |\sin(2beta+gamma)|> 0.62
(0.35) at 68% (90%) confidence level.
