N-*S acyl transfer

Macmillan D, Adams A, Premdjee B (2011) Shifting native chemical ligation into reverse through N— S acyl transfer. Isr J Chem 51 885-899... 

Premdjee B, Adams AL, Macmillan D (2011) Native A-glycopeptide thioester synthesis through N— S acyl transfer. Bioorg Med Chem Lett 21 4973 975... 

As shown, under the reducing ligation conditions, 0—>S acyl transfer occurred at the o-disulfide phenolic ester as previously described (see above), to provide the thioester, which underwent transthioesteriflcation with the thiol-containing glyco-peptide (upon in situ reduction of the auxiliary disulfide bond) the transient intermediate underwent an S N acyl transfer to generate the thermodynamically favored amide bond of the doubly glycosylated peptide adduct. The auxiliary was subsequently removed through sequential methylation of the fi-ee thiol to prevent the reverse acid-mediated N S acyl shift, followed by TFA treatment. 

Reissert s compound (l-cyano-l,2-dihydroquinolinyl benzamide) is apparently de-protonated under phase transfer conditions at the one-carbon as expected. The condensation of the carbanion with an aldehyde or ketone leads to an N-benzoyl alk-oxide in which oxygen acylation (N ->0 acyl transfer) results in five-membered ring formation. The intermediate oxazolidine decomposes with loss of cyanide to give the benzoate ester of an isoquinolinoylcarbinol as shown in equation 10.26 [36]. 

We were also able to use FAB mass spectrometry to determine the amino acid sequence around the active site serine in the acyl transference domain of rabbit mammary fatty acid synthase.6 The synthase was labelled in the acyl transferase domain(s) by the formation of O-ester intermediates after incubation with [" " C]-acetyl- or malonyl-CoA (Fig. 2A). The modified protein was then digested with elastase (Fig. 2B), and radioactive material isolated via successive purification steps on Sephadex G-50 and reverse phase HPLC. The isolated peptides were then sequenced by FAB MS. The data summarized in Table II established the sequences of both the acetyl and malonyl hexapeptides to be N-acyl-Ser-leu-Gly-Glu-Val-Ala. 

One of the first effective chiral PPY derivatives to be developed for asymmetric acyl transfer was catalyst 7, which was shown by Fuji and Kawabata in 1997 to be effective for the acylative KR of various racemic mono-benzoylated ds-diol derivatives [76]. Subsequently, it was also successfully applied in the KR of N-protected cyclic ds-amino alcohols [77]. Using 5 mol% of PPY 7 in the presence of a stoichiometric amount of collidine in CHCI3 at rt, a variety of cyclic ds-amino alcohol derivatives were resolved with moderate selectivities (s = 10-21) (Table 8.6). 

Better for the lateral lithiation of phenols are the N,N-dialkylcarbamate derivatives 444. These may be lithiated with LDA, allowing complete selectivity for the lateral position, presumably because this is the thermodynamic product.192 With s-BuLi ortholithiation is the predominant reaction pathway. If the lateral organolithium 445 is warmed to room temperature, an acyl transfer from O to C takes place, analogous to the anionic ortho-Fries (see section 2.3.2.1.4), giving amide 446.365... 

Figure 18.11 Auxiliaries used in the N to S to acyl transfer to construct peptide thioesters.

Kim MG, Lee SB (1996) Penicillin acylase-catalyzed synthesis of P-lactam antibiotics in water-methanol mixtures effect of cosolvent content and chemical nature of substrate on reaction rates and yields. J Mol Catal B Enzym 1 201-211 Kohsaka M, Domain AL (1976) Conversion of penicDlin N to cephalosporin(s) by ceU-free extracts of Cephalosporium acremonium. Biochem Biophys Res Commun 70(2) 465-473 Koreishi M, Tani K, Ise Y et al. (2007) Enzymatic synthesis of P-lactam antibiotics and /V-fatty-acylated amino compounds by the acyl transfer reaction catalyzed by peniciUin V acylase from Streptomyces mobaraensis. Biosci Biotechnol Biochem 71(6) 1582-1586 Kupka JY, Shen, YQ, Wolfe S et al. (1983) Partial purification and properties of the alpha-ketoglutarate-linked ring expansion enzyme of beta-lactam biosynthesis of Cephalosporium acremonium. FEMS Microbiol Lett 16 1-6... 

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