Amines acylations

C-7 Amino Acylation. Essentially all the known methods for amine acylation, used in the peptide field, have been apphed to cephalospotins. 

Amine Acyl Azide Amide Bond Azide Leaving... 

The hydrated dihydropyrimidotriazines 323 were prepared from the pyrimidine 321 by sequential amination and cyclization or by sequential amination, acylation, and cyclization [80JCR(S)278], Thus, acylhydra-zines reacted with pyrimidine 321 to give acylhydrazinopyrimidines 322, which then were cyclized by treatment with aqueous sodium hydrosulfite to give 323. They were found to be inactive as enzyme inhibitors. 

FIGURE 4.14 Reactions of activated A-alkoxycarbonylamino acids in the presence of tertiary amine. Acyl halides and mixed and symmetrical anhydrides generate 2-alkoxy-5(4/7)-oxazolone in the presence of tertiary amine. Aminolysis of 2-alkoxy-5(47f)-oxazolone in the presence of E N led to partially epimerized products. OAct = activating group. 

First-Order Rate Constants for Amine Acylation by p-Nitrophenyl Esters"- ... 

Transglutaminases can recognize a broad range of primary amine acyl-acceptor substrates in vitro. However, recognition of the acyl-donor substrate in vivo is restricted to the y-carboxyamide of glutamine within an apparently relatively small subset of sequence contexts... 

Pencillin G acylase from E. coli is functionally, but not structurally, related to lipases. The enzyme would find wider use if it could be rendered tolerant of low-water media, which is the kind of problem that ionic liquids were expected to solve. It was found, however, that a covalently immobilized penicillin acylase, PGA 450, required aw = 0.8, which also was the minimum in toluene, to stay active in the ionic liquids [BMIm][BF4], [OMIm][BF4], and [BMIm][PF6] [67]. In a simple amine acylation test reaction (Figure 10.4), PGA 450 was somewhat less active in ionic liquids than in toluene. 

Amine Acyl chloride Amide Hydrochloride salt... 

Primary or secondary amine Acyl chloride Tetrahedral intermediate Amide... 

To recycle a valuable amine acylation catalyst, Janda and co-workers10 attached a proline-based catalyst to a polymeric support for the enan-tioselective kinetic resolution of alcohols (entry 6). The resin-bound catalyst behaves similarly to the soluble catalyst, providing good yields of secondary alcohols and their corresponding esters with good to excellent enantioselectivities for various substrates. 

The iterative route to these porphyrin-core dendrimers employed the readily available ethereal building block 163.11911 Thus, amine acylation (DCC, 1-HBT, THF) of monomer 163 (Scheme 4.46) with tetraacid 166 afforded the first tier dodecaester 167a, which upon termini transformation (LiOH, Me0H/H20 (1 1)) of the polyester gave the polyacid 167b. Repetition of this sequence allowed the construction of two additional tiers, e.g., ester 168. 

---