Sang Hyup Lee

Design and synthesis of new mitomycin dimers containing a seven-membered cyclic disulfide and a diol linkers

We report the design and synthesis of two new mitomycin dimers, 7-N,7′-N′-(1″,2″-dithiepanyl-3″,7″-dimethylenyl)bismitomycin C (8) and 7-N,7′-N′-(2″,6″-dihydroxy-1″,7″-heptanediyl)bismitomycin C (9). Mitomycins 8 and 9 are dimers connected by a seven-membered cyclic disulfide (a 1,2-dithiepane) and a 2,6-dihydroxyheptane linkers, respectively. Mitomycin 8 was designed to undergo efficient nucleophilic activation and following alkylation to give DNA adducts such as DNA interstrand cross-link (DNA ISC) adducts. The key moiety in 8 is a seven-membered cyclic disulfide linker that can generate two thiol groups in a molecule through disulfide cleavage. The two thiols can serve as probes to activate two mitomycin rings by intramolecular cyclization to quinone rings. The mitomycin 8 was synthesized using mitomycin A (1) and the key intermediate, cyclic disulfide 11 that was prepared through a nine-step synthetic sequence from 1,6-heptadiene (12). The diol mitomycin 9 was also synthesized from 1 and diamine salt 15.

Synthesis and biological evaluation of 3-substituted 5-benzylidene-1-methyl-2-thiohydantoins as potent NADPH oxidase (NOX) inhibitors.

We report the synthesis of novel 3-substituted 5-benzylidene-1-methyl-2-thiohydantoins 3, and their biological evaluation using NADPH oxidase (NOX) 1 and 4. Based on structural and pharmacophore analyses of known inhibitors such as hydroxypyrazole 2, we envisioned interesting 2-thiohydantoin compounds, 3-substituted 5-benzylidene-1-methyl-2-thiohydantoins 3 that would be expected to well match the structural features in 2. Efficient synthesis of eighteen target compounds 3 were achieved through the synthetic pathway of 4→11→3, established after consideration of several plausible synthetic pathways. The inhibitory activities of compounds 3 against NOX 1 and 4 were measured, with some of the target compounds showing similar or higher activities compared with reference 2; in particular, compounds 3bz, 3cz, and 3ez were found to be promising inhibitors of both NOX 1 and 4 with modest isozyme selectivities, which highlights the significance of the 2-thiohydantoin substructure for inhibition of NOX 1 and 4. This marks the first time these compounds have been applied to the inhibition of NOX enzymes.

Studies on activation mechanism of a mitomycin dimer, 7-N,7′-N′-(1″,2″-dithiepanyl-3″,7″-dimethylenyl)bismitomycin C

We report the studies on nucleophilic activation and DNA alkylation of a cyclic disulfide mitomycin dimer, 7-N,7′-N′-(1″,2″-dithiepanyl-3″,7″-dimethylenyl)bismitomycin C (6) along with a diol mitomycin dimer, 7-N,7′-N′-(2″,6″-dihydroxy-1″,7″-heptanediyl)bismitomycin C (7). We wished to see if disulfide mitomycin 6 undergoes efficient nucleophilic activation and corresponding formation of DNA interstrand cross-link (DNA ISC) products compared to diol mitomycin 7. Mitomycin 6 is a dimer connected by a seven-membered cyclic disulfide (a 1,2-dithiepane) linker, and mitomycin 7 is also a dimer containing 2,6-dihydroxyheptane linker that was employed as a reference one to identify the effect of disulfide unit in 6. Through kinetic studies using solvolysis reaction, we found that 6 underwent much faster nucleophilic activation by Et3P compared to 7, and that the enhanced activation rates were induced by the disulfide unit in 6. These findings led us to propose a nucleophilic activation mechanism for 6. We further demonstrated that 6 produced much higher levels of DNA ISC (86%) by the action of Et3P compared with 7 (5%) and 1 (4%). Therefore, we have concluded that 6 was highly efficient for nucleophilic activation and DNA ISC formation due to the key role of cyclic disulfide unit in 6.

Design, synthesis, and mode of action studies of a mitomycin tetramer inducing double activations with a single probe

We report design, synthesis, and mechanistic studies of a new mitomycin tetramer 9 along with a new mitomycin dimer 10. Mitomycin 9 is a tetramer connected by the disulfide linker 11, and easily undergoes disulfide cleavage to provide two dimeric structures 9r that each contains a single thiol probe for activations. So, tetramer 9 as a precursor of 9r was specifically targeted to undergo double activations with a single probe. A tetramer 9 was synthesized using 1 and key intermediate 11, and a dimer 10 was synthesized from 1 and diamine 12. Activation studies revealed that 9 underwent effective double activations with a single probe by nucleophiles while the reference 10 did not. Evaluations of DNA ISC formations showed that 9 generated substantial levels of DNA ISC by nucleophilic activation while the references 10 and 2 did not. The effectiveness of 9 in activation and formation of DNA ISC per probe was verified by comparing with dimers 5-8 of double activations with two probes. These findings highlighted the role of a single thiol in 9r and demonstrated the intended double activations with a single probe, which marks the first case in mitomycin studies.