  We study the phenomenological constraints and consequences in the flavor
sector, of introducing a new fourth generation $\mathcal{Z}_{2}$ odd
vector-like lepton doublet along with a Standard Model (SM) singlet scalar and
an $SU(2)_{L}$ singlet scalar leptoquark carrying electromagnetic charge of
$+2/3$, both odd under a $\mathcal{Z}_{2}$. We show that with little fine
tuning among the various Yukawa couplings in the new physics (NP) Lagrangian
along with the CKM parameters, the model is able to push the theoretical value
of $R(D^{*})^{th}$ from $0.252 \pm 0.003$ to $0.263 \pm 0.051$ and $R(D)^{th}$
from $0.300 \pm 0.008$ to $0.313 \pm 0.158$ compared to the SM value.
Especially the NP contributions are able to reduce the discrepancy between
experiment and theory of $R(D^{*})$ substantially compared to SM. This is quite
impressive given that the model satisfy all other very stringent constrains
coming from neutral meson oscillations and precision $Z$-pole data.
