Diastereosedepends on the structure of both the diene position is not generally predictable, simply because it strongly the structure of each the diene and dienophile. Much more predictable diasterediastereoseoselective constructionstructure of both oxabicyclic structures could be performed utilizing lectivedepends around the of functionalized oxabicyclic structures might be predictable applying building of functionalized the diene and dienophile. Far more lective construction of functionalized oxabicyclic structures may well be performed making use of HMF-derived 2,5-disubstituted furans that predominantly react with cyclic alkenes with predominantly react with cyclic alkenes with HMF-derived two,5-disubstituted furans that predominantly react with Florfenicol-d3 Inhibitor higher endoselectivity (Table 4, entries 1; Table 5, entry 24) [33,43,106,108]. cyclic alkenes with high endoselectivity (Table four, entries 1; Table 5, entry 24) [33,43,106,108]. higher endoselectivity (Table 4, entries 1; Table 5, entry 24) [33,43,106,108].1, 22, x FOR PEER REVIEWInt. J. Mol. Sci. 2021, 22, x FOR PEER REVIEWInt. J. Mol. Sci. 2021, 22,14 of12 ofTable 6. IMDA cycloadditions FAM ML169 Autophagy derivatives with cyclic alkenes. Table 6. IMDA cycloadditions ofofFAM derivatives with cyclic alkenes.Table 6. IMDA cycloadditions of FAM derivatives with cyclic alkenes.1 2 1 three 2 4 3 five four 6RDienophileConditions Et20, 23 Conditions H3BO3/PEG-400, 90 Et2 0, 23 C Circumstances H3BO3/PEG-400, 90 H3 BO3 /PEG-400, 90 C H3BO3/PEG-400, 90 H3 BO3 /PEG-400, 90 C Toluene, 50 H3 BO3 /PEG-400, 90 C Benzene, C Et20, 23 Toluene, 50 RTBenzene, RTSelectivity Exo Selectivity Exo Exo Exo Exo Exo Exo Exo Exo Exo ExoExoAc Maleic anhydride R Dienophile Ac Maleimide Ac Maleic Dienophile anhydride Ac N-Ph-maleimide Ac Maleimide Ac N-(4-Chlorobenzyl)maleimide Ac N-Ph-maleimide Boc 1 Maleic anhydride Ac N-(4-Chlorobenzyl)maleimide 1 1 Boc Thiomaleic Maleic anhydride anhydride Maleic anhydride BocBocYield of Adducts, [ref.] Yield of one hundred, [109] Adducts, [Ref.] 84, [110] 100, [109] Selectivity 78, [110] 84, [110] 92, [110] 78, [110] 92,94, [111] [110] Exo 68, [112] 94, [111]68, [112]YieldMaleimide H3BO /PEG-400, 90 Exo 7 Boc 1 Endo/exo (1:three.4) 7 EtOAc, reflux 85, [113] Boc N-Ph-maleimide H3BOEtOAc, reflux 90 Endo/exo (1:3.four) 3/PEG-400, Exo 85, [113] N-(4-Chlorobenzyl)maleimide H3BO3/PEG-400, 90 Exo tert-Butyloxycarbonyl. tert-Butyloxycarbonyl. Maleic anhydride Toluene, 50 Exo Examples of DA reactions of furfural derivatives containing acceptor-type substituThiomaleic anhydride Benzene, RT Exo Examples of DA reactions of furfural derivatives containing acceptor-type substituentsThiomaleic anhydridewith with alkenes uncommon. Just after the reaction ofof 2-furoic acidwith -alanine-substituted ents alkenes are are rare. Right after the reaction 2-furoic acid with -alanine-substituted maleimide, only a little volume of one isomer was detected 40 C right after h [26]. Inmaleimide, only a compact amount of one isomer was detected at at 40 just after 128128 h [26]. Interestingly, quite low equilibrium continual for this reaction was observed in DMF media, terestingly, a an extremely low equilibrium constantfor this reaction was observed in DMF media, EtOAc, reflux Endo/exo (1:three.four) although the equilibrium continuous in water was at the very least two orders of magnitude greater. This whilst the equilibrium constant in water was at the least two orders of magnitude higher. This distinction was explained by the statement that water features a significant effect on the entropy a important impact around the entropy difference was explained by t.