The molar ratio of vinyl hexanoate to helicid as 7.5 (Table two, entry 9). Frequently, substrate molecules are a lot more active at greater reaction temperatures. On the other hand, high temperature would induce the comformational changes in the enzyme, thus decreasing the enzyme activity. Therefore, the impact of temperature around the reaction was examined. The reaction showed a broad temperature profile with an optimum at 45uC (entries 9 and 12?16). From these data, the optimum circumstances of enzyme dosage, molar ratio of vinyl hexanoate to helicid and reaction temperature were 20 U, 7.5 and 45uC, respectively, along with the regioselectivity with the reaction remained fantastic beneath all situations tested.Time Course of Enzymatic Reaction and Operational StabilityTo get a deeper insight into the enzymatic progress, the time course of caproylation of helicid catalyzed by lipase TLL was followed under the optimum conditions described above. Substrate conversion increased quickly with reaction time, and reached its maximum at 1.5h (Figure 2A). The lipase TLLTable two. Optimization of enzymatic caproylation of helicid.Entry 1 2 three four five six 7 8 9 10 11 12 14 15Enzyme dosage (U) five ten 15 20 25 30 20 20 20 20 20 20 20 20VB (eq.) five five 5 5 5 5 1.five three 7.five ten 15 7.5 7.five 7.5 7.T (6C) 40 40 40 40 40 40 40 40 40 40 40 35 45 50V0 (mM/h) three.four 11.9 16.two 24.four 25.1 26.2 6.9 16.two 30.3 31.four 32.two 26.7 33.2 33.5 33.C ( )97 98 .99 .99 .99 .99 58 89 .99 .99 .99 .99 .99 .99 .6′-Regioselectivity ( ) .99 .99 .99 .99 .99 .99 .99 .99 .99 .99 .99 .99 .99 .99 .Reactions conditions: 0.02 mmol helicid. doi:10.1371/journal.pone.0080715.tPLOS One | plosone.orgRegioselective Route to Helicid EstersFigure two. Time course of enzymatic caproylation and operational stability of Thermomyces lanuginosus lipase. Reactions circumstances: 0.02 mmol helicid, 0.15 mmol vinyl hexanoate, 20 U Thermomyces lanuginosus lipase, 2 ml anhydrous THF, 45uC, 200 rpm. Symbols: (h) the conversion, (g) the regioselectivity, ( ) the relative activity. doi:10.1371/journal.pone.0080715.gshowed the higher operational stability with 28 loss in activity soon after eight cycles from the reaction (Figure 2B).Regioselective Acylation of Helicid with Different Acyl DonorsThe acylation of helicid with various fatty acid vinyl esters catalyzed by lipase TLL was investigated in anhydrous THF (Table 3).1250997-29-5 web Interestingly, in all cases lipase TLL displayed practically absolute 6′-regioselectivity (.99 ), since only the 6′-ester of helicid could be detected by NMR and HPLC, that is similar for the acylation of sucrose, rutin, esculin, isoquercitrin and arbutin Table three. Enzymatic synthesis of different esters of helicid.using a notable selectivity for 6′-hydroxyl of your glucose moiety [8,9,16,17,18]. This regioselectivity may well occur since the lesshindered main hydroxyl on the sugar moiety may possibly more easily enter in to the active web page of your lipase to attack the acyl-enzyme intermediate than the other additional hindered hydroxyl groups, hence resulting in the preferential formation of 6′-esters.Price of 1-(2-Hydroxy-5-iodophenyl)ethan-1-one As shown in Table 2, the initial reaction price enhanced with all the elongation of chain length of vinyl esters from C2 to C8 (Table three, entries 1?), maybe simply because medium chain-length acyl groups can kind stronger interactions with all the hydrophobic acyl binding web-site of your enzyme than shorter-chain acyl groups [19,20].PMID:23341580 Entry 1 2 3 four 5 6 7 eight 9Acyl donor Vinyl acetate (C2) Vinyl propionate (C3) Vinyl butyrate (C4) Vinyl hexanoate (C6) Vinyl caprylate (C8) Vinyl decanoate (C10) Vinyl laurate (C1.
