Af-acetylation

Three types of synthases catalyze the addition of phosphoenolpyruvate (PEP) to aldoses or the corresponding terminal phosphate esters. By concurrent release of inorganic phosphate from the preformed enolate nucleophile, the additions are essentially irreversible. None of the enzymes are yet commercially available and little data are available oil the individual specificities for the aldehydic substrates. A bacterial NeuAc synthase (EC 4.1.3.19) has been used for the microscale synthesis of A -acetylncuraminic acid from Af-acetyl-D-mannosamine31 and its 9-azido analog from 2-acetamido-6-azido-2,6-dideoxy-D-mannose32. 

PhsSnflV)] complexes of N-Ac-Gly, Af-acetyl-leucine, N-acetyl-asparagine, and N-Ac-L-Tyr were prepared by two procedures and characterized by means... 

Figure E 14.4b shows the results of the application of the optimization strategy to solvated Af-acetyl-Af -methyl-alanineamide. Level sets of the deviations of the total energy from the global minimum are shown as solid and dashed lines at 1, 2, 5, and...

DPT (239) with a mixture of acetic anhydride, ammonium nitrate and nitric acid at 65-70 °C furnishes HMX in 65 % yield after purification. Bachmann and co-workers repeated the method of Wright and co-workers but obtained a slightly lower yield of HMX (59 %) after puritication of the crude product from both RDX (16 % total of the crude) and linear Af-acetyl nitramine by-products. Another procedure treated DPT (239) with 1.6 mole equivalents of ammonium nitrate and 3.2 equivalents of fuming nitric acid at 60-65 °C and is reported to furnish HMX in 75 % yield after purification. "... 

We propose that the first step in NDP-kasugamine biosynthesis is 2-epimeriza-tion of the postulated UDP-A -acetyl-D-glucosamine precursor, which is suggested by the similarity of the KasQ protein with known UDP-(Af-acetyl-)D-glucosamine 2-epimerases and catalyzes the conversion to UDP-N-acetyl-D-mannosamine. To... 

MolI14.15c ForD 302 11828 Fms2( ) Af-acetyl hexosaminyl deacetylase or amidase... 

D-galactosyl-(o -l,3-L-fucosyl)-Af-acetyl-D-glucos-aminyl-R. Unlike the galactoside 3(4)-L-fucosyltransfer-ase [EC 2.4.1.65] above, this enzyme exhibits no action on the corresponding 1,3-galactosyl derivative. 

Af-acetyl-D-maimosamine (67), but the intermediate 72 can undergo an epimeriza-tion to 74 (Scheme 11) through the formation of 73 before the Michael addition took place, as observed by Wen and Hulting in the preparation of C-linked glycophosphonates [122]. 

Using optimized conditions (pentanedione 2 equiv., NaHCOs 4 equiv., H2O-THF 2 1, 90°C, 24 h), Ai-acetyl-o-glucosamine (66) gave the gluco- and manno ketones 69a and 70a in a 4 6 ratio and 83% yield, whereas Af-acetyl-o-mannosa-mine (67) led to the same products in a 3 1 ratio and 40% yield. This poor yield has been explained by the instability of 70a in the reaction mixture. These compounds were easily separated by crystallization of their acetylated derivatives 69b and 70b. Applied to A-acetyl-D-galactosamine (68), the same reaction conditions gave the C-glycosidic ketone 71a, isolated as the acetylated compound 71b (Fig. 12, Table 4). 

Scheme 11 Possible intermediates involved in the reaction of Af-acetyl-D-glucosamine (66) and W-acetyl-D-mannosamine (67)...

Derivatives of partially unsaturated six-membered N-heterocycles have been investigated. In the Af-acetyl- and N-benzoylazacyclohex-2-enes and in the analogs 130 with X = O, S, CO, internal rotation of the N-acyl group can be studied (77CJC949 840MR676) independently of ring inversion, the... 

Inhibition of premature LH surges in women undergoing controlled ovarian hyperstimulation NA Af-acetyl-3-(2- naphthyl)-D- alanyl-4-chloro-D- phenylalanyl-3-(3- pyridyl)-D-alanyl-L- seryl-L-tyrosyl-9 N 9, AflO-diethyl-D- NA... 

Af-Acetyl-L-alaninamide [15062-47-7] M 130.2, m 162°. Crystd repeatedly from EtOH-ethyl ether. 

N 103 "A Comparison of the CHARMM, AMBER, and ECEPP Potentials for Peptides. II Acetyl Alanine IV-Methyl Amide ... 

Thermal decomposition of 143 gave Af-acetyl-3-acetoxyindole, and subsequent hydrolysis with aqueous sodium hydroxide provided indigos in 86-96% yield. 

Hydrolyzes chitobiose and higher analogs and protein derivatives by removing Af-acetyl-n-glucosamine from the non reducing end A /S-D-glucuronide + HzO — alcohol + D-glucuronic acid... 

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