Supplementary MaterialsFile 1: Experimental and analytical data. this study lay the foundation for Mouse monoclonal to TEC future design strategies toward more potent HDACis for HDAC8 isozymes and further therapeutic applications for neuroblastoma. value DAPT kinase activity assay of 15 Hz (Supporting Information File 1, Physique S3). Open in a separate window Scheme 1 Reaction conditions: a) MeOH, H2SO4 (5 drops), MS 4 ? (2 pieces), 68 C, 8 h, 81%; b) DIBAL-H (1.2 equiv), 6 h, ?78 C, THF, 78%; c) phosphorane 8 (2.0 equiv), THF, 8 h, 60 C, 72%; d) SeO2, dioxane, 110 C, 8 h, 61%; e) indolamine 10 (1.1 equiv) DCE, sodium triacetoxyborohydride (STAB, 1.1 equiv), TEA (2 equiv), rt, 63%; f) NaOH at ?10 C, NH2OHH2O at ?10 C, MeOH , rt, 12 h, 55%. Next, oxidation of the methyl group of 7 under SeO2 conditions at 110 C provided the ethyl acrylate aldehyde 9 in 61% yield. The next step involved the crucial reductive amination reaction between aldehyde 9 with indolamine 10, which had been obtained via Fischer indole synthesis C the reaction of phenylhydrazine with 5-chloro-2-pentanone . Initial reduction attempts using sodium triacetoxyborohydride (STAB) as the reducing agent provided predominantly starting material and negligible potential product as monitored by TLC. However, addition of 2 equivalents of triethylamine to the reaction mixture facilitated the formation of the product, compound 11 in 63% yield. The product was confirmed by 1H NMR and 13C NMR as shown in Supporting Information File 1. Finally, the ethyl ester 11 was converted to the hydroxamic acid derivative, TOI1 using the bidentate nucleophile hydroxylamine either under neutral or basic conditions [36C37]. We first explored neutral conditions where aqueous hydroxylamine was added to compound 11 in methanol, and a predominant polar spot was observed by TLC. However, the isolated product was not the expected TOI1, as 1H NMR revealed two new peaks at 4.53 and 2.66 ppm (Supporting Information File 1, Figure S36) presumably indicating that a favorable Michael addition followed by intramolecular cyclization or vice versa provided compound 12, which was validated by 13C and DEPT NMR studies (Supporting Information File 1 Figures S37and S38). Marred with these observations, compound 11 was treated with aqueous hydroxylamine in the presence of strong bottom (i.e., 10 equivalents of methanolic sodium hydroxide or aqueous sodium hydroxide) at 0 C. The response was supervised by TLC and it uncovered that methanolic sodium hydroxide supplied a cleaner response than aqueous sodium hydroxide circumstances. The response blend was quenched using a saturated ammonium chloride option at 0 C after 12 h, the solvent was evaporated, as well as the substance was put through reversed-phase column chromatography using C-18 silica gel. After preliminary unsuccessful purification protocols with drinking water/THF or drinking water/ACN solvent systems, we determined an optimized drinking water/methanol mixture to supply the pure item TOI1 in 55% produce. The isolated compound was seen as a spectroscopic techniques. Having create response circumstances for the formation of TOI1 effectively, we then concentrated our efforts in the generation of regioisomers TOI2 and TOI3-rev, respectively. Initial attempts to oxidize the methyl group at the benzylic position in starting materials 2 and 3 to provide the corresponding aldehyde compounds 13 and 14 failed, despite using rigorous DAPT kinase activity assay reaction conditions of SeO2 or option strong oxidizing brokers (e.g., MnO2 and oxone). Thus, we considered the critical role of the electronic effects of the nitrogen atoms on this cyclic substrate, and then we revised our synthetic strategy by a) tethering an alkene functional group around the aromatic ring and b) then conducting the oxidation of the benzylic group to afford the aldehyde product. Towards this end, we performed a Suzuki coupling reaction between boronic acid 15 with chloro compound 2 (Scheme 2). To the best of our knowledge, there is no report of a Suzuki coupling reaction using boronic acid 15 in the literature. However, we generated this required boronic acid from the corresponding methyl propiolate . Open in a separate window Scheme 2 Reaction conditions: a) DAPT kinase activity assay boronic acid 15 (1.3 equiv), PdCl2(PPh3)2 (0.1 equiv), dioxane/H2O (3:1), Na2HPO4 (2.0 equiv), TEA (4.0 equiv), 90 C, 15 h, 55% for 16 and 71% for 18; b) SeO2 , different conditions, 0%; c) SeO2 (2.0 equiv), dioxane, 110 C, 12 h, 54%. Next we investigated reaction conditions for the reaction of compound 2 with boronic acid 15 using different variables (Supporting Information File 1, Table S1). Gratifyingly, after surveying several reaction conditions, we successfully obtained the desired product 16 in 35% yield using PdCl2(PPh3)2 and Na2HPO4 as the base in a dioxane/water system under heating conditions of 90 C. To improve the.