Density functional theoretical studies on photoswitching and charge migration dynamics of thio and selenoureidopeptides

Density functional theoretical calculations have been performed to investigate the changes in electronic structure at ground and excited states of ureidopeptides on substitution with higher chalcogens like sulphur and selenium for oxygen. This replacement results in a reduced preference towards the intramolecular hydrogen bonding interaction, thus linear conformers are found to be stable at both states. Nevertheless, conformational switching observed during this process is mainly due to n to �* transition that leads to the dihedral angle � change from trans to cis with a rotational barrier of 10 to 17 kcal mol-1. The computed barrier is lesser than that reported for oxopeptides (20 kcal mol-1). And, the hole migration dynamics after immediate ionization illustrates that the hole originated at ureido end evolves in time (2�4 fs) while the hole generated at the carboxylate end will not evolve as reported for ureidopeptides. The usage of these candidates as photoswitches has also been explored. Copyright © 2017 John Wiley & Sons, Ltd

ChemInform Abstract: A Facile Synthesis of N‐Z/Boc‐Protected 1,3,4‐Oxadiazole‐Based Peptidomimetics Employing Peptidyl Thiosemicarbazides.

A convenient protocol is presented for the cyclization of dipeptidyl thiosemicarbazides (III)

Staudinger/aza-Wittig Reaction to Access Nβ-Protected Amino Alkyl Isothiocyanates

A unified approach to access Nβ-protected amino alkyl isothiocyanates using Nβ-protected amino alkyl azides through a general strategy of Staudinger/aza-Wittig reaction is described. The type of protocol used to access isothiocyanates depends on the availability of precursors and also, especially in the amino acid chemistry, on the behavior of other labile groups towards the reagents used in the protocols; fortunately, we were not concerned about both these factors as precursor-azides were prepared easily by standard protocols, and the present protocol can pave the way for accessing title compounds without affecting Boc, Cbz and Fmoc protecting groups, and benzyl and tertiary butyl groups in the side chains. The present strategy eliminates the need for the use of amines to obtain title compounds and thus, this method is step-economical; additional advantages include retention of chirality, convenient handling and easy purification. A few hitherto unreported compounds were also prepared, and all final compounds were completely characterized by IR, mass, optical rotation, and 1H and 13C NMR studies

T3P® (propylphosphonic anhydride) Mediated Conversion of Carboxylic Acids into Acid Azides and one-pot Synthesis of Ureidopeptides

A general, mild, efficient, and environmentally benign protocol, which makes use of T3P® as an acid activating agent for the direct synthesis of acid azides from carboxylic acids is described. Further, the protocol is employed for the one-pot synthesis of α-ureidopeptides starting from N-protected α-amino acids

Ethyl 2-[N-(2-formyl­phen­yl)benzene­sulfonamido]acetate

In the mol­ecule of the title compound, C17H17NO5S, the two aromatic rings are oriented at an angle of 30.13 (10)°. The ethyl acetate group assumes an extended conformation. Mol­ecules are linked into C(7) chains running along the a axis by inter­molecular C—H⋯O hydrogen bonds, and the chains are crosslinked via C—H⋯π inter­actions, with the sulfonyl-bound phenyl ring acting as an acceptor

Desymmetrization of meso-Dibromocycloalkenes through Copper(I)-Catalyzed Asymmetric Allylic Substitution with Organolithium Reagents

The highly regio- and enantioselective (up to >99:1 dr, up to 99:1 er) desymmetrization of meso-1,4-dibromocycloalk-2-enes using asymmetric allylic substitution with organolithium reagents to afford enantioenriched bromocycloalkenes (ring size of 5 to 7) has been achieved. The cycloheptene products undergo an unusual ring contraction. The synthetic versatility of this Cu(I)-catalyzed reaction is demonstrated by the concise stereocontrolled preparation of cyclic amino alcohols, which are privileged chiral structures in natural products and pharmaceuticals and widely used in synthesis and catalysis

Challenges and opportunities in remote prototyping: a case-study during COVID-19

Collaboration is common practice within design disciplines and beyond. Brainstorming, discussions, and prototyping tend to occur within the same physical space. The reduction of human interaction during the COVID-19 pandemic disrupted these practices. In this paper, we focus on the possibilities and challenges of remote prototyping of four student teams by combining a double diamond approach with tools to overcome remote work challenges. The results were analyzed to understand crucial tools, advantages, and obstacles. The key challenges and opportunities were then identified and examined

Stereospecific Ring Contraction of Bromocycloheptenes through Dyotropic Rearrangements via Nonclassical Carbocation-Anion Pairs

Experimental and theoretical evidence is reported for a rare type I dyotropic rearrangement involving a [1,2]-alkene shift, leading to the regio- and stereospecific ring contraction of bromocycloheptenes. This reaction occurs under mild conditions, with or without a Lewis acid catalyst. DFT calculations show that the reaction proceeds through a nonclassical carbocation-anion pair, which is crucial for the low activation barrier and enantiospecificity. The chiral cyclopropylcarbinyl cation may be a transition state or an intermediate, depending on the reaction conditions

ChemInform Abstract: T3P® (Propylphosphonic Anhydride) Mediated Conversion of Carboxylic Acids into Acid Azides and One‐Pot Synthesis of Ureidopeptides.

The method is high-yielding and ecofriendly