Topochemistry for Difficult Peptide-Polymer Synthesis: Single-Crystal-to-Single-Crystal Synthesis of an Isoleucine-Based Polymer, a Hydrophobic Coating Material.

Polymers of hydrophobic amino acids are predicted to be potential coating materials for the creation of hydrophobic surfaces. The oligopeptides of hydrophobic amino acids are called "difficult peptides"; as the name suggests, it is difficult to synthesize them by conventional methods. We circumvented this synthetic challenge by adopting topochemical azide-alkyne cycloaddition (TAAC) polymerization of a hydrophobic dipeptide monomer.

Rational design and topochemical synthesis of polymorphs of a polymer.

Packing a polymer in different ways can give polymorphs of the polymer having different properties. β-Turn forming peptides such as 2-aminoisobutyric acid (Aib)-rich peptides adopt several conformations by varying the dihedral angles. Aiming at this, a β-turn-forming peptide monomer would give different polymorphs and these polymorphs upon topochemical polymerization would yield polymorphs of the polymer, we designed an Aib-rich monomer N-(Aib)-NHCH-C[triple bond, length as m-dash]CH.

Synthesis of novel seven-membered carbasugars and evaluation of their glycosidase inhibition potentials.

Here, we report the synthesis of five novel seven-membered carbasugar analogs. We adopted a chiral-pool strategy starting from the cheap and readily available d-mannitol to synthesize these ring-expanded carbasugars. Apart from several regioselective protecting group manipulations, these syntheses involved Wittig olefination and ring-closing metathesis as the key steps.

Secondary Structure Tuning of a Pseudoprotein Between β-Meander and α-Helical Forms in the Solid-State.

Tuning the secondary structure of a protein or polymer in the solid-state is challenging. Here we report the topochemical synthesis of a pseudoprotein and its secondary structure tuning in the solid-state. We designed the dipeptide monomer N -Leu-Ala-NH-CH -C≡CH (1) for topochemical azide-alkyne cycloaddition (TAAC) polymerization.

Designed Synthesis of a 1D Polymer in Twist-Stacked Topology via Single-Crystal-to-Single-Crystal Polymerization.

To synthesize a fully organic 1D polymer in a novel twist-stacked topology, we designed a peptide monomer HC≡CCH -NH-Ile-Leu-N , which crystallizes with its molecules H-bonded along a six-fold screw axis. These H-bonded columns pack parallelly such that molecules arrange head-to-tail, forming linear non-covalent chains in planes perpendicular to the screw axis. The chains arrange parallelly to form molecular layers which twist-stack along the screw axis.

Spontaneous Single-Crystal-to-Single-Crystal Evolution of Two Cross-Laminated Polymers.

Two cases of spontaneous evolution of monomers to linear polymers having novel cross-laminated topology are reported. We synthesized two peptide monomers N -Gly-Gly-NH-CH -CCH and N -Gly-Gly-Gly-CH -CCH and solved their crystal structures by single-crystal X-ray diffraction. They adopt H-bonded crisscrossed layered packing in their crystals such that: (a) the monomers are aligned head-to-tail in 1D-chain-like arrays and parallel arrangement of such arrays forms a layer; (b) the proximally placed azide and alkyne motifs are in an orientation apt for their regiospecific cycloaddition; (c) each monomer having x peptide bonds is H-bonded with 2x monomers disposed in intersecting arrangement, which pre-organize 1D-chain-like arrays in adjacent layers in perpendicular orientation.

Correction: A versatile glycosylation strategy Au(iii) catalyzed activation of thioglycoside donors.

[This corrects the article DOI: 10.1039/C6SC00633G.].

A versatile glycosylation strategy Au(iii) catalyzed activation of thioglycoside donors.

Among various methods of chemical glycosylations, glycosylation by activation of thioglycoside donors using a thiophilic promoter is an important strategy. Many promoters have been developed for the activation of thioglycosides. However, incompatibility with substrates having alkenes and the requirement of a stoichiometric amount of promoters, co-promoters and extreme temperatures are some of the limitations.