Thiols auxiliary

A new thiol auxiliary (45, R = COEt) participates in boron-mediated anti-aldol reactions with aldehydes with high yield and de.124 Reaction of the product with (g> nucleophiles displaces it (in the form of the thiol, 45 R = H), converting the aldol product under mild conditions into esters, thiolates, phosphonates, alcohols, or acids. 

Initial studies directed at overcoming the requirement of an A-terminal cysteine in NCL led to the development of two thiol auxiliaries, l-aryl-2-mercaptoethyl and 4,5,6-trimethoxy-2-mer-... 

Recently, another cysteine-free ligation strategy has been reported for the synthesis of glycopeptides. The method, dubbed sugar assisted ligation (SAL), utilizes a peptide thioester and a glycopeptide in which the carbohydrate is derivatized with a thiol auxiliary at the C-2 acetamide [52,53]. The proposed mechanism of this ligation, depicted in Scheme 7, involves... 

Fig. 10.2-6 Auxiliary mediated native chemical ligation, (a) trans thioesterification, S-to-acyl tranfer, removal of auxiliary, (b) Tmb auxiliary (c) Z-phenylethane thiol auxiliary.

The first example of ligation via side-chain auxiliary, termed sugar-assisted ligation (SAL), was developed by Wong and coworkers in 2006 and involved the use of a glycopeptide whereby the reactive thiol auxiliary was appended to the C-2... 

Intramolecular to S Acyl Shift Reaction 2.1 At the Thiol Auxiliary, Dmmb... 

A thiol auxiliary, Dmmb mediated thioester formation, above, and a cysteine residue might also play a role in the formation of a thioester. It was suggested that a thioester is formed during the treatment of a protected cysteine-containing peptide with anhydrous hydrogen fluoride [57]. In order to confirm the formation of... 

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