We further found that our flow protocol was not limited to the synthesis of simple phenol-based fluorosulfates. In fact, we observed that a wide variety of natural products, drugs, and fluorescent tracers could be successfully reacted using this approach. For instance, N-Bocprotected tyrosine, broxyquinoline, fluorescein, α-tocopherol, estrone, and unprotected amoxicillin were all cleanly converted in just 2 minutes of reaction time (Figure , compounds 7-12), demonstrating the excellent functional group tolerance of our method. Similarly, the challenging class of nitrogen-based nucleophiles could also be subjected to our protocol delivering the corresponding sulfamoyl fluorides in excellent isolated yields. For example, 4to 7-membered ring secondary amines (Figure , compounds 13-17), heterocyclic derivatives (Figure , compounds 18-20), and an aniline compound (Figure , compound 21) were effectively reacted with SO2F2. Our flow protocol was also effective in synthesizing analogs of several pharmaceutically relevant molecules, such as stanozolol, paroxetine, desloratadine, amoxapine, and olanzapine, which rapidly yielded the desired SuFExed products (Figure , compounds 22-26). Additionally, nucleosides such as adenosine and cytidine derivatives (Figure , compounds 27-29) could be used as competent reaction partners. Finally, we were able to use bidentate nucleophiles, such as BINOL, catechol, and salicylamide (Figure , compounds 30-32), to produce the corresponding sulfates and sulfamates. generation: SO2Cl2 (2 equiv, 0.2 M in CH3CN) passed through a 3.8 mL cartridge filled with a 1:1 mixture of KF and glass beads. Standard conditions for the second step: [a] Nucleophile (1 equiv, 0.2 M in CH3CN), Et3N (2.5 equiv). [b] Nucleophile (1 equiv, 0.2 M in DMF), Et3N (2.5 equiv). [c] The compound has been isolated after an acetylation step. [d] Nucleophile (1 equiv, 0.2 M in CH3CN), DBU (4.0 equiv). [e] Nucleophile (1 equiv, 0.2 M in DMF), DBU (4.0 equiv). Next, we capitalized on the modular nature of our setup and developed a multistep process that orchestrates several reactions in a sequential fashion (Figure ). For instance, we streamlined a three-module flow setup to synthesize sulfate derivative 33 (67%) uninterrupted. After generating sulfuryl fluoride in the packed-bed reactor and trapping it with estrone in the SuFEx capillary reactor, the resulting fluorosulfate was reacted with (4-iodophenoxy)trimethylsilane in a second SuFEx capillary. Our flow approach carefully balances the stoichiometry of the gaseous reagent, preventing any remaining SO2F2 from unproductively consuming the silyl ether in the second SuFEx step . Furthermore, after a solvent switch, the reaction crude can also immediately be used to carry out a base-promoted hydrolysis of ethylenacetal-protected estrone to obtain bisulfate derivative 34 (80% yield) or a palladium-catalyzed Suzuki-Miyauratype cross coupling to yield product 35 in 55% yield. Our flow approach has demonstrated excellent functional group tolerance and selectivity in producing SuFExed products from various small molecules. This is due to the favorable reaction conditions, including high mass transfer and excellent dosing of gaseous reagents, provided by the flow protocol that allows for reduced reaction times of just two minutes, thereby avoiding the formation of deleterious byproducts. We next sought to explore the potential of our microfluidic strategy for the late-stage modification of unprotected peptides . Our aim was to directly install the sulfur-centered electrophilic handle within the peptide core, allowing for later SuFEx-enabled derivatization opportunities . Based on our previous experience with small molecules, we anticipated that the reaction would be kinetically favored for tyrosine residues, which should enable site-selective modification within the complex peptidic framework. After a minimal re-optimization of the reaction conditions (see Supplementary Materials), we investigated the reactivity of different nucleophilic amino acid residues within different pentapeptides. We found that tyrosine-containing peptides were successfully converted in a site-selective fashion in just two minutes (Figure , compounds 36 and 37). Our evaluation also showed limited modification at lysine and histidine (Figure , compounds 38 and 39), while other nucleophilic residues, such as tryptophan and cysteine, were not reactive under our reaction conditions (see Supplementary Materials). Encouraged by these results, we subjected various complex and therapeutically valuable peptides to our flow protocol. Cyclic peptides (Figure , compounds 40 and 41) and therapeutic drugs such as Angiotensin II and Bivalirudin (Figure , compounds 42 and 43) were selectively modified at the tyrosine residue in good to excellent results. Even natural peptides, such as α-Endorphin and β-Amyloid (1-28), were effectively converted into the corresponding fluorosulfates with good to excellent conversions (Figure , compounds 44 and 45).