Fig. 4. Late-stage modification of multifunctional substrates. ^aGeneral reaction conditions: 1 (0.10 mmol), 2 (0.20 mmol), Mes-Acr⁺ (0.005 mmol), TPA (0.010 mmol), and TFA (0.20 mmol) were reacted in dichloromethane (DCM; 2.0 mL) at room temperature under blue LED irradiation for 3 h. Yield is isolated yield unless otherwise noted. ^b1.2 equiv. of the aldehyde was used. The target compound was isolated as the lactone. ^cThe reaction was conducted at the 0.035 mmol scale.