  Let $G$ be a simply connected simple algebraic group over $\mathbb{C}$ of
type $B_r$, $B$ and $B_-$ be its two opposite Borel subgroups, and $W$ be the
associated Weyl group. For $u$, $v\in W$, it is known that the coordinate ring
${\mathbb C}[G^{u,v}]$ of the double Bruhat cell $G^{u,v}=BuB\cap B_-vB_-$ is
isomorphic to an upper cluster algebra
$\overline{\mathcal{A}}(\textbf{i})_{{\mathbb C}}$ and the generalized minors
$\Delta(k;\textbf{i})$ are the cluster variables of ${\mathbb
C}[G^{u,v}]$[A.Berenstein, S.Fomin, A.Zelevinsky, Duke Math. J. 126 (2005),
1-52, arxiv:math.RT/0305434]. Recently, it is also shown that ${\mathbb
C}[G^{u,v}]$ have structure of cluster algebra [K. R. Goodearl, M. T. Yakimov,
arxiv:1602.00498 (2016)]. In the case $v=e$, we shall describe the generalized
minor $\Delta(k;\textbf{i})$ explicitly.
