First, we evaluated the hydrolytic stability of each compound under aqueous conditions and an enzymatic condition. We prepared aqueous solutions of the compounds (10 µM, 0.1% DMSO) at various pH conditions or in the presence of carboxylesterase. Subsequently, we monitored the timedependent hydrolysis of the compounds using thin-layer chromatography (TLC). While the ester compound was gradually hydrolyzed at higher pH levels, carbamate compounds were stable under such conditions (Supplementary Figure ). The most labile ester, 1, was fully converted into the corresponding hydrolyzed product after only one min of incubation with carboxylesterase (Figure ). Carbamate analog 2 was also hydrolyzed by carboxylesterase, but the hydrolysis reaction was substantially slower than that of Ester 1. Notably, silyl-substituted carbamate 3 was far more stable against enzymatic hydrolysis than 1 and 2. The hydrolytic product of carbamate 3 was not observed until 2.5 h after incubation. Our results are consistent with those of a previous report, suggesting that steric protection around carbonyl bonds can enhance hydrolytic stability because of the introduction of bulky substituents. Next, we quantitatively evaluated the time-dependent photolysis of each compound using high performance liquid chromatography-mass spectrometer (HPLC-MS) (Figure ). To assess photolysis of the coumarin derivatives, we irradiated 405 nm light (6.6 mW/cm 2 ) to the aqueous solutions of each compound, then monitored the abundance of each compound by detecting the signal intensity at target mass using HPLC-MS. In all compounds, we observed a time-dependent decrease in the mass signal intensity of the starting material upon irradiation, accompanied by an increase in the corresponding photolytic products (Supplementary Figure ). Ester 1 exhibited faster photolysis than the corresponding carbamate analog 2 because the resulted anionic species from 1 should be further stabilized compared to 2. Notably, we observed a rapid decrease in the mass signal intensity of silyl-substituted carbamate 3 compared to 2. This result strongly suggests that the remote silyl group on 3 stabilizes the excited cation species through the β-silyl effect, which contributes to the acceleration of photolysis. Thus, we successfully demonstrated that our molecular design featuring a remote silyl group enhanced both hydrolysis resistance and photolytic efficiency through steric protection and established β-silyl orbital effect on cation stabilization, respectively.