Amino thiols from aldehydes

Ring-opening hydrolysis of thiazolidines under acidic or basic conditions gives aldehyde and amino thiol. Peptidyl aldehydes 111 were synthesized in excellent yields from thiazolidine peptides 112 using copper salts (CuO, CUCI2) in acetonitrile/water under the reducing conditions (Scheme 39) <1997TL2459>. 

In 2004, Yang and Tseng reported the synthesis of a series of new chiral amino thiol ligands derived from L-valine, which were further employed (1 mol%) in the enantioselective alkenylzinc addition to aldehydes, providing an efficient route for chiral ( )-allylic alcohols with enantioselectivities of up to >99% ee, as shown in Scheme 3.67. ... 

Penicilloic acid 5, the substrate for the projected lactamization reaction, could be derived from the suitably protected intermediate 6. Retrosynthetic disassembly of 6, in the manner illustrated, provides D-penicillamine hydrochloride (7) and tert-butyl phthalimido-malonaldehydate (8) as potential building blocks. In the synthetic direction, it is conceivable that the thiol and amino groupings in 7 could be induced to converge upon the electrophilic aldehyde carbonyl in 8 to give thiazolidine 6 after loss of a molecule of water. 

Peptide thioesters (Section 15.1.10) are generally prepared by coupling protected amino acids or peptides with thiols and are used for enzymatic hydrolysis. Peptide dithioesters, used to study the structures of endothiopeptides (Section 15.1.11), may be prepared by the reaction of peptide nitriles with thiols followed by thiolysis (Pinner reaction). Peptide vinyl sulfones (Section 15.1.12), inhibitors of various cysteine proteases, are prepared from N-protected C-terminal aldehydes with sulfonylphosphonates. Peptide nitriles (Section 15.1.13) prepared by dehydration of peptide amides, acylation of a-amino nitriles, or the reaction of Mannich adducts with alkali cyanides, are relatively weak inhibitors of serine proteases. 

Many interactions are of a pure chemical nature and may result from the presence of aldehydes and their reactivity toward amino and thiol groups of proteins. Another frequently occurring type of interaction is the formation of hydrogen bonds between food compounds and polar flavor components such as alcohols. Starch, starch-derived maltodextrins, and (3-cyclodextrin are able to form inclusion complexes with many flavor components. Many other interactions, although of great influence on flavor perception, are of a physical nature and therefore not mentioned in this chapter. 

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