- Enzyme mediated-transesterification of verbascoside and evaluation of antifungal activity of synthesised compounds
-
Enzymatic acylation of verbascoside, a polyhydroxylated natural product, has been reported in this study using five different commercial lipases and taking p-nitrophenyl alkanoates as acyl donors. Out of these enzymes, the immobilised Candida antarctica lipase B was found as the enzyme of choice. Mono-and di-acylated products were formed, with mono as major product indicating high regioselective nature of such transformations. A series of acyl esters of verbascoside have been synthesised by this enzymatic transesterification methodology. The lipophilicity of the synthesised analogues was also checked. The analogues were further subjected to synergistic antifungal activity with amphotericin B (AmB) against Candida albicans. Fourfold reduction in minimum inhibitory concentration of AmB was observed with few synthesised analogues such as verbascoside 4″-octanoate (3b), verbascoside 4″-palmitate (3d) and verbascoside 4″,4′-dipalmitate (4d) at a concentration of 0.5 g/mL.
- Khazir, Jabeena,Ali, Intizar,Khan, Inshad Ali,Sampath Kumar, Halmuthur Mahabalarao
-
-
Read Online
- Selective Decarbonylation of Fatty Acid Esters to Linear α-Olefins
-
Selective decarbonylation of p-nitrophenol esters of fatty acids to the corresponding linear α-olefins (LAOs) was achieved using palladium catalysis. After extensive ligand screening, a mixed-ligand system exploiting the trans-spanning diphosphine XantPhos and an N-heterocyclic carbene (IPr) was identified as the most effective in yielding high α-selectivity and high conversions of the ester (>98% selectivity, >90% conversion using 2.5 mol % of PdCl2 and 5 mol % of the ligands, 190 °C, 2-2.5 h). On the basis of insights from modeling at the density functional level of theory, we propose that the mixed-ligand set achieves high α-selectivity by promoting olefin dissociation from the palladium center following β-hydride elimination, which is especially facilitated both by the combined steric bias of the mixed-ligand set and by the ability of the XantPhos ligand to coordinate in both mono- and bidentate fashions.
- John, Alex,Dereli, Büsra,Ortunìo, Manuel A.,Johnson, Hillis E.,Hillmyer, Marc A.,Cramer, Christopher J.,Tolman, William B.
-
p. 2956 - 2964
(2017/08/21)
-
- Fingerprint lipolytic enzymes with chromogenic p-nitrophenyl esters of structurally diverse carboxylic acids
-
A series of structurally diverse chromogenic esters, including a new compound (4-nitrophenyl 2-methylpentanoate), has been synthesized, constituting an array of 17 substrates which could be applied to rapidly fingerprint the activity of lipases or esterases to reveal their substrates specificity and functional characteristics. Combined with genetic technology such as "data mining" and directed evolution, such fingerprints might be a promising platform for discovery of potentially useful enzymes in industrial application. The fingerprint of commercially available Lipase-B from Candida antarctica as a model enzyme was first measured to confirm the reliability of this method. Then three new enzymes mined from genomic libraries were successfully fingerprinted, revealing the functional characteristics of those enzymes. Among them, the enzyme SrfAD was founded with specific substrate preference towards cycloalkyl carboxylic esters and aromatic esters, making it more promising in synthetic utilities than other tested enzymes.
- Qian, Le,Liu, Jia-Yan,Liu, Jia-Ying,Yu, Hui-Lei,Li, Chun-Xiu,Xu, Jian-He
-
experimental part
p. 22 - 26
(2012/02/06)
-
- HIGHER N-ACYL-L-AMINO ACID DERIVATIVES
-
A preparative method is proposed for obtaining higher N-acylamino acids by reaction of free amino acids with fatty acid nitrophenyl esters.It was shown that these acids can transport positive ions through a liquid lipophilic medium.A direct method is proposed for obtaining fatty acid 4-nitrophenyl esters by boiling 4-nitrophenol and the fatty acid in xylene in a Soxhlet apparatus in the presence of an acid catalyst.
- Kochetkov, K. A.,Urmambetova, Zh. S.,Belikov, V. M.,Bakasova, Z. B.
-
p. 2311 - 2316
(2007/10/02)
-
- CHIMIE DES SUCRES SANS GROUPEMENTS PROTECTEURS-I-ESTERIFICATION REGIOSELECTIVE DE L'HYDROXYLE ANOMERE DU LACTOSE, DU MALTOSE ET DU GLUCOSE
-
Treatment of acyl chlorides 4 with mercaptothiazoline, mercaptobenzothiazole, p-nitrophenol and 8-hydroxyquinoline in the presence of Et3N, afforded high yields of the corresponding reactive amides 5a-h,S-thioesters 6e-h and aryl esters 7e-h and 8a-h, respectively.The esters 6e-h, 7e-h and 8e-h reacted with excess β-lactose in pyridine, to give the corresponding β-esters 9e-h resulting from esterification of the anomeric hydroxyl of the sugar.The amides 5c, f-h gave the α-lactosyl esters 9c, f-h.The amide 5e and the esters 8b, c, e reacted with β-maltose, thus affording the corresponding β-maltosyl esters 10b, c, e, whereas the compounds 8a-e reacted with β-glucose, yielding the corresponding β-glucosyl esters 11a-e.This appears to be one of the very few selective chemical modifications of sugars known, which do not involve the toilsome protection-deprotection methology.The now commercially available maltosyl and glucosyl esters 10e and 11d-e are new non-ionic, and water soluble detergents which could be used for studies of cell membrane proteins.
- Plusquellec, Daniel,Roulleau, Fabienne,Bertho, Francoise,Lefeuvre, Martine,Brown, Eric
-
p. 2457 - 2468
(2007/10/02)
-
- CHIMIE DES SUCRES SANS GROUPEMENTS PROTECTEURS: ESTERIFICATION REGIOSELECTIVE DE L'HYDROXYLE ANOMERE DU LACTOSE LIBRE
-
Treatment of α-lactose with acyl chlorides failed to give any pure products.However, the anomeric hydroxyl of lactose was esterified selectively and in high yields, by treating the free sugar with reactive acylating agents such as N-acyl thiazolidine-thiones or esters of p-nitrophenol, mercapto-benzothiazole and 8-hydroxy quinoline, making thus unnecessary the preliminary protection of the other hydroxyls of the lactose molecule.This appears to be one of the very few selective modifications of sugars known, which do not involve the classical protection-deprotection methodology.
- Roulleau, Fabienne,Plusquellec, Daniel,Brown, Eric
-
p. 719 - 722
(2007/10/02)
-
