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Although amyloids are a well-known pathological structure, functional amyloids are beneficial. Functional amyloids can be engineered to cultivate desired functionality that can destroy malicious amyloids. However, not much is known about such amyloid destructors. On the other hand, nearly all approaches to developing a drug against pathogenic amyloidoses have failed. Therefore, novel approaches are needed. Herein, a rationally designed catalytic triad based "proteolytic functional amyloid (PFA)" formed by linking a target protein recognizing unit with a Gly-integrated non-native Glu-His-Cys segment is reported. The proteolytic mechanism of the designed PFA is boosted by thiol/disulfide exchange cleavage. Rigorous MALDI-TOF and FRET-based analyses indicated that the PFAs cleaved Aβ12-21 (model Aβ) and the pathogenic Aβ1-40 site selectively in vitro. PFA significantly inhibited the aggregation of Aβ1-40 and broke-down the preformed fibrillar amyloids into non-toxic metabolites. Such a platform may be helpful in not only the on-demand chemical degradation of pathogenic amyloids but also the targeted degradation of other malicious proteins. PFAs are the first "amyloid-destroying" amyloids. [ABSTRACT FROM AUTHOR]

An improved, one‐pot two‐step process is described to convert carboxylic acid to amides, dipeptides, esters, and hydroxamates using Oxyma and thionyl chloride. The addition of Oxyma to thionyl chloride in the presence of Hunig's base results in a mixture of probably Oxyma‐sulfinyl chloride and sulfinyl diOxyma, two new intermediates, which successfully converts the carboxylic acid into its Oxyma ester. Adding a nucleophile to the generated Oxyma ester leads to corresponding amide, ester, or hydroxamic acid formation at room temperature. The procedure is mild and well tolerant to various carboxylic acids, including N‐protected amino acids and different nucleophiles such as methyl esters of amino acids and alcohols. 32 examples with moderate to good yield (67–86 %) are reported. A rigorous mechanism investigation is performed using 1H and 13C‐NMR. By‐product Oxyma can be recovered and recycled. Thionyl chloride has been used for such coupling reactions in industries and academia for a few hundred years to date. Nevertheless, minimum racemization, side reaction, and waste generation make the addition of Oxyma (this methodology) a valuable improvement. [ABSTRACT FROM AUTHOR]

An improved, one‐pot two‐step process is described to convert carboxylic acid to amides, dipeptides, esters, and hydroxamates using Oxyma and thionyl chloride. The addition of Oxyma to thionyl chloride in the presence of Hunig's base results in a mixture of probably Oxyma‐sulfinyl chloride and sulfinyl diOxyma, two new intermediates, which successfully converts the carboxylic acid into its Oxyma ester. Adding a nucleophile to the generated Oxyma ester leads to corresponding amide, ester, or hydroxamic acid formation at room temperature. The procedure is mild and well tolerant to various carboxylic acids, including N‐protected amino acids and different nucleophiles such as methyl esters of amino acids and alcohols. 32 examples with moderate to good yield (67–86 %) are reported. A rigorous mechanism investigation is performed using 1H and 13C‐NMR. By‐product Oxyma can be recovered and recycled. Thionyl chloride has been used for such coupling reactions in industries and academia for a few hundred years to date. Nevertheless, minimum racemization, side reaction, and waste generation make the addition of Oxyma (this methodology) a valuable improvement. [ABSTRACT FROM AUTHOR]

A method for Beckmann rearrangement using ethyl 2‐cyano‐2‐(2‐nitrobenzenesulfonyloxyimino) acetate (o‐NosylOXY) under microwave irradiation is reported. Ketoximes (19 examples) are converted to the corresponding amides/lactams with 69–97% yields in ∼10 minutes without any Lewis acid or co‐catalyst. This is an example of halogen‐free organocatalytic Beckmann rearrangement. Nuclear magnetic resonance (NMR)‐ and high‐resolution mass spectrometry (HRMS)‐based detailed mechanistic investigation suggest that o‐NosylOXY acts as an initiator. Such initiators are reported before based on density functional theory (DFT) calculations. However, we report here the HRMS signatures of two transient intermediates, the nitrilium ion and the nitrilium ion's dimeric species. Rigorous NMR‐based investigation of the reaction mechanism is performed. Our results indicate that the reported Beckmann rearrangement proceeds via two consecutive rearrangements. [ABSTRACT FROM AUTHOR]

The self‐assembly of N‐ and C‐protected alternating L/L and D/L amino acids containing dipeptides, Boc‐L‐Val‐L‐Ile‐OMe (1), Boc‐D‐Val‐L‐Ile‐OMe (2), Boc‐L‐Ile‐L‐Val‐OMe (3), and Boc‐L‐Ile‐D‐Val‐OMe (4) has been investigated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images indicated that 1 and 3 self‐associated to form highly organized straight net microrods, whereas 2 and 4 self‐assembled to form hexagonal hollow microtube‐like architecture in the acetonitrile‐water medium. To understand the physical basis of such differential behavior, we performed X‐ray diffraction pattern analyses. The single‐crystal X‐ray diffraction (SC‐XRD) study revealed that 1 and 2 self‐assembled to form slightly different helix‐like architectures. The higher‐order association of 2 exhibited a hollow hexagonal tube‐like superstructure. The thermal stability of the nanostructures also varied based on the chiroptical composition of the dipeptides. Experimental findings were corroborated well with computational studies. The obtained results may be helpful in nano‐biotechnology as well as in material science. [ABSTRACT FROM AUTHOR]

A mild, practical, and straight forward method for Boc deprotection and its use in peptide synthesis both in solution and on solid support is presented. Boc protecting group is removed from the N‐terminal amino acid of the amino acid and the peptide using environment‐friendly cost‐effective Lewis acid, FeCl3. The deprotected amino group undergoes C−N bond formation with the next Boc‐protected amino acid in the presence of a suitable coupling reagent and base. A library of di‐ to tetrapeptides is synthesized with moderate to good yield from standard and nonstandard Boc‐protected amino acids in solution. Most importantly, this protocol can be used for the solid‐phase peptide synthesis (SPPS) using Boc‐protected amino acids on the acid‐sensitive Rink amide resin, which is usually used for Fmoc chemistry. This protocol thus allows practicing Boc chemistry in a greener manner, and on‐demand switching from Fmoc to Boc chemistry and vice‐versa while synthesizing one oligopeptide on the same resin. The inherent orthogonality of Fmoc and Boc chemistry allows facile synthesis of branched and cyclized peptides on the resin as well. [ABSTRACT FROM AUTHOR]