In this paper, for each
$n\geqslant g\geqslant 0$ we consider the moduli stack
$\widetilde{{\mathcal{U}}}_{g,n}^{ns}$ of curves
$(C,p_{1},\ldots ,p_{n},v_{1},\ldots ,v_{n})$ of arithmetic genus
$g$ with
$n$ smooth marked points
$p_{i}$ and nonzero tangent vectors
$v_{i}$ at them, such that the divisor
$p_{1}+\cdots +p_{n}$ is nonspecial (has
$h^{1}=0$) and ample. With some mild restrictions on the characteristic we show that it is a scheme, affine over the Grassmannian
$G(n-g,n)$. We also construct an isomorphism of
$\widetilde{{\mathcal{U}}}_{g,n}^{ns}$ with a certain relative moduli of
$A_{\infty }$-structures (up to an equivalence) over a family of graded associative algebras parametrized by
$G(n-g,n)$.