N-Transacylation

Isomers, Rearrangement Trans... s. a. Interc iange Transacetalation 26, 223 N-Transacylation s. Transamidation O-Transalkylation s. Transetherification Transamidation -, via N-acylcarboxylic acid amides 27, 476... 

The stereochemistry of N-transacylation of 1,l-bis(acylamido)-l-deoxy-alditols using carboxylic anhydrides has been studied. 

Poly(methyl 3-(l-oxypyridinyl)siloxane) was synthesized and shown to have catalytic activity in transacylation reactions of carboxylic and phosphoric acid derivatives. 3-(Methyldichlorosilyl)pyridine (1) was made by metallation of 3-bromopyridine with n-BuLi followed by reaction with excess MeSiCl3. 1 was hydrolyzed in aqueous ammonia to give hydroxyl terminated poly(methyl 3-pyridinylsiloxane) (2) which was end-blocked to polymer 3 with (Me3Si)2NH and Me3SiCl. Polymer 3 was N-oxidized with m-ClC6H4C03H to give 4. Species 1-4 were characterized by IR and H NMR spectra. MS of 1 and thermal analysis (DSC and TGA) of 2-4 are discussed. 3-(Trimethylsilyl)-pyridine 1-oxide (6), l,3-dimethyl-l,3-bis-3-(l-oxypyridinyl) disiloxane (7) and 4 were effective catalysts for conversion of benzoyl chloride to benzoic anhydride in CH2Cl2/aqueous NaHCC>3 suspensions and for hydrolysis of diphenyl phosphorochloridate in aqueous NaHCC>3. The latter had a ti/2 of less than 10 min at 23°C. 

The feasibility of bonding pyridinyl groups to silicon which contains a hydrolytically sensitive functional group has recently been demonstrated 15-71. 2-Fluoro-3-(dimethylchlorosilyl)pyridine and 3-fluoro-4-(dimethylchloiosilyl)pyridine as well as 2-, 3-, and 4-(dimethylchlorosilyl)pyridine were prepared by the reaction of the corresponding lithiopyridines with excess Me2SiCl2- Hydrolysis of the pyridinyl substituted chlorosilanes gave disiloxanes which were insoluble in water. In the present report we will describe extension of this work to include pyridinyl dichlorosilanes which can be hydrolyzed to polysiloxanes. These polymers can be N-oxidized and the resultant derivatives have been shown to be effective hydrophobic transacylation catalysts. 

Cacciapaglia, R., van Doom, A.R., Mandolini, L., Reinhoudt, D.N. and Verboom, W. (1992) Differential metal ion stabilization of reactants and transition states in the transacylation of crown ether aryl acetates./. Am. Chem. Soc.. 114, 2611. 

Acetyl-l-benzyl-3,4,4a,5,6,7-hexahydro-l,5-naphthyridine-2,7(l//)-dione (15) (a byproduct from a primary synthesis) appears to have undergone partial dehydrogenation and N— (9-transacylation to afford 7-acetoxy-l-benzyl-3,4-dihydro-1,5-naphthyridin-2( 1 //)-one (16) (Pd/C, xylene, 130°C, 30 h ... 

Acylation of triazolates is expected to occur at N-1 but transacylation by displacement of an electrophilic substituent from N-1 might be predicted to proceed by attack of the electrophile on N-4. The actual course of the reaction may be explained on the analogy of isotopic studies on imidazole (66CB2955) applied to triazole (Scheme 28) the first product of the sequence is the mixed anhydride (84) that reacts with the liberated triazole at N-1 to afford benzoyltriazole (85) and the unstable carbamic acid (86). 

The inhibition of hLAL by boronic acids and diethyl p-nitrophenyl phosphate (Sando and Rosenbaum, 1985 G. N. Sando and H. L. Brockman, unpublished, cited by Anderson and Sando, 1991) indicates that hLAL is a serine hydrolase. Two lipase/esterase consensus pentapep-tides, G-X-S-X-G, are found, but only one of them appears to be consistent with the packing requirements of the )8-eSer-a nucleophilic motif (see above). Susceptibility of the enzyme to sulfhydryl reagents, and the requirement of thiols for the stability of purified hLAL, prompted Anderson and Sando (1991) to propose that a cysteine residue, or rather a Cys/Ser couple, may be involved in an internal transacylation reaction. It must be pointed out, however, that hLAL has all three cysteines of the gastric enzyme (as well as six additional ones), and so the inhibitory Cys is also there. The same argument proposed herein with respect to hGL, i.e., that a free cysteine is topologically close to the active site, also holds for hLAL. 

Some interesting transformations were described for N-substituted A-ary I hydroxyl -amines. The a-aminohydroxamic acids 180 rearranged in the presence of amines to give A - acy lo x y ary I am i n es 181 (N O transacylation)273 (equation 71). 

The oxime resin has also been proven to be labile to hydroxy-containing compounds such as N-hydroxypiperidine, N-hydroxysuccinimide and N-hydroxyben-zotriazole at 50-70 °C [46]. The corresponding active esters of peptides were transacylated to amino containing resins [47]. Another N-hydroxy resin, N-hydroxysuccinimide active ester resin, has been described for the synthesis of amide products. Bound esters were successfully cleaved even with secondary amines in high yields and purities [48]. 

AP833>, and 3-acyl-3,4,5,6-tetrahydro-l,3-thiazine-2-thiones (59) are formed in the same way from the parent 3,4,5,6-tetrahydro-l,3-thiazine-2-thiones (60) (Equation (7)) <84AP74>. Both types of product are unstable and can be used as transacylating agents for amines and thiols. Thiocarbamoyl chlorides also react with 3,4,5,6-tetrahydro-l,3-thiazin-2-ones, but here both N- and (9-thio-carbamoylation can occur <86LA1140>. 

Activation of carboxylic acids. The coupling reagent 1, derived from N-methylmorpholine and 2-chloro-4,6-dimethoxy-l,3,5-triazine, reacts with RCOOH to form heteroaryl esters that are susceptible to alcoholysis and serve as transacylating agents in peptide synthesis. ... 

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