The training can be monitored using the loss values computed from eq1-7 in the BGAN output (Supporting Information, Figure ). Upon convergence, the pseudo-molecular configurations generated from BGAN are used for evaluating the entropy for a conformational ensemble. Second, the pseudo-molecular configurations are used to evaluate configurational entropy along a user-defined reaction coordinate based on entropic path sampling method. The pseudomolecular configurations generated using BGAN are divided into multiple ensembles (i.e., ten by default) that are consecutively spaced along a user-defined reaction coordinate. For each ensemble, the configurational entropy is computed with 3𝑁 -6 DoFs that are selected to maximize the overall configurational entropy (Supporting Information, Text S2). The maximum information spanning tree (MIST) approximation is applied to compute higher-order entropy terms. The resulting entropic profile will be computed relative to the first truncated ensemble near transition state (Supporting Information, Table and). sampling. The CP dimerization QCT simulations were performed by using B3LYP/6-31G(d) method in Gaussian 09; the NgnD-Catalyzed Diels-Alder QCT simulations were performed by using B3LYP-D3/6-31G(d) method in Gaussian16. For each sampled geometry, real normal vibrational modes were energized with zero-point energy plus a Boltzmann sampling of the thermal energy available at 298K with a random phase. The QCTs were propagated forward and backward with a velocity-Verlet algorithm using Singleton's Progdyn program with 1 fs step length of integration until either product or reactant were formed (bond formation cutoff: 1.6 Å for the C-C bond formation). For CP dimerization, we acquired 2,480 QCTs each for the dimerized product with the formation of bond 2 or bond 3. For NgnD-catalyzed Diels-Alder reaction in gas-phase, we acquired 100 QCTs each for the formation of [4+2]-adduct or [6+4]adduct.