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A protected tripeptide Boc-l-Leu-5-AIA-Aib-OMe was synthesized where 5-aminoisophthalic acid (5-AIA), a rigid non-coded aromatic γ-amino acid is incorporated as central residue. The single crystal X-ray diffraction study indicates that the peptide self-assembles into supramolecular sheet through intermolecular hydrogen bonding interaction N–H⋯O and π···π interaction. [ABSTRACT FROM AUTHOR]

Pseudopeptides are a versatile class of organic building blocks having potential applications in a wide range of domains. In the current study, N and C termini protected l-alanine based short pseudopeptide was synthesized, where 5-aminoisophthalic acid (5-AIA), a rigid non-proteogenic γ-amino butyric acid was incorporated as C-terminal residue. The single crystal X-ray analysis revealed that the l-Ala residue of the aforesaid peptide adopts ϕ and ψ values characteristic of polyproline II conformation. Self-assembly of the pseudopeptide seems to represent a supramolecular helical architecture via NH⋯O, CH⋯O hydrogen bonding and π–π interactions. [ABSTRACT FROM AUTHOR]

An achiral tripeptide, namely, Boc-γ-Abu-m-ABA-Aib-OMe (γ-Abu: γ−amino butyric acid; m-ABA: meta-aminobenzoic acid) was synthesized by solution phase procedure. The α, γ-hybrid peptide was designed in such a way that two dissimilar γ−amino acids, one flexible and another rigid, were positioned sidewise along with α-amino isobutyric acid (Aib) as C-terminal residue. The single crystal X-ray diffraction analysis revealed that two kinks were generated around centrally placed m-ABA. Interestingly, the peptide self-assembled via three intermolecular N–H···O and one intermolecular C–H···O hydrogen bonding interactions to supramlecular helical architecture. [ABSTRACT FROM AUTHOR]

A tripeptide Boc-L-Pro-m-ABA-Aib-OMe was synthesized where meta-aminobenzoic acid (m-ABA), a rigid non-coded γ-amino acid is placed as middle residue. Single crystal X-ray diffraction study indicates that the peptide self-assembles into helical motif through intermolecular hydrogen bonding interaction N–H···O, C–H···O, π···π interaction and van der Waals interaction. HR-TEM image reveals the formation of fibril in the solid state. [ABSTRACT FROM AUTHOR]

N-(N-benzoyl glycinyl)-N,N′-dicyclohexylurea was synthesised by conjugating N-benzoyl glycine and dicyclohexylcarbodiimide (DCC) using triethylamine as base catalyst. A single crystal X-ray diffraction study reveals that the compound self-assembles into a supramolecular sheet structure by intermolecular N–H · · · O, C–H · · · O hydrogen bonding and non-bonding van der Waals interactions. A high resolution transmission electronic microscopic (HR-TEM) image of the compound exhibits formation of fibrils in the solid state. [ABSTRACT FROM AUTHOR]

While the terminally protected tripeptide Boc-Phe-Gly-m-ABA-OMe I (m-ABA, meta-amino benzoic acid) is an excellent gelator of aromatic organic solvents, another similar tripeptide Boc-Leu-Gly-m-ABA-OMe II, where the Phe residue of peptide I is replaced by Leu, cannot form gels with the same solvents. The morphology of the gels of peptide I, characterised by the field-emission scanning electron microscopy and high-resolution transmission electron microscopy, reveals the formation of nanofibrous networks which are known to encapsulate solvent molecules to form gels. The wide-angle X-ray scattering studies of the gels suggest the β-sheet-mediated self-assembly of peptide I in the formation of a nanofibrous network, where π-stacking interactions of Phe play an important role in the self-assembly and gel formation. The dried gel of peptide I observed between crossed polarisers after binding with a physiological dye, Congo red, shows a bluish-green birefringence, a characteristic of amyloid fibrils. [ABSTRACT FROM AUTHOR]

Abstract: Single crystal X-ray diffraction studies reveal that the incorporation of meta-amino benzoic acid in the middle of a helix forming hexapeptide sequence such as in peptide I Boc-Ile(1)-Aib(2)-Val(3)-m-ABA(4)-Ile(5)-Aib(6)-Leu(7)-OMe (Aib: α-amino isobutyric acid; m-ABA: meta-amino benzoic acid) breaks the helix propagation to produce a turn-linker-turn (T-L-T) foldamer in the solid state. In the crystalline state two conformational isomers of peptide I self-assemble in antiparallel fashion through intermolecular hydrogen bonds and aromatic π–π interactions to form a molecular duplex. The duplexes are further interconnected through intermolecular hydrogen bonds to form a layer of peptides. The layers are stacked one on top of the other through van der Waals interactions to form hydrophilic channels filled with solvent methanol. [Copyright &y& Elsevier]

Abstract: Single crystal X-ray diffraction studies and solvent dependent NMR titration reveal that the designed peptides I and II, Boc-Xx(1)-Aib(2)-Yy(3)-NH(CH2)2NH-Yy(3)-Aib(2)-Xx(1)-Boc, where Xx and Yy are Ile and Leu in peptide I and Leu and Val in peptide II, respectively, fold into a turn-linker-turn (T-L-T) conformation both in the solid state and in solution. In the crystalline state the T-L-T foldamers of peptide I and II self-assemble to form a three-dimensional framework of channels. The insides of the channels are hydrophilic and found to contain solvent CHCl3 hydrogen bonded to exposed Clocated at the turn regions. [Copyright &y& Elsevier]

A set of three peptides 1-3 of general formula PhCO-Gly-Xx-OCH2Ph, where Xx is Gly in peptide 1, Ala in 2 and Aib (α-animo isobutyric acid) in 3 has been chosen to study the selfassembly and the morphology of the solid biomaterials. FT-IR and single crystal X-ray diffraction studies reveal that the peptides 1-3 self-assemble to form supramolecular β-sheet structures through intermolecular hydrogen bonds and aromatic π-π interactions. Field emission scanning electron micrographs (FE-SEM) of the dried materials of the peptides 1-3 show the formation of flat ribbon like structures which are formed through β-sheet mediated selfassembly. [ABSTRACT FROM AUTHOR]

The pseudopeptide Gly-m-ABA (m-ABA = m-amino benzoic acid) has been chosen to study the formation of supramolecular structures through self-assembly. Single crystal X-ray diffraction studies reveal that the pseudopeptide Boc-Gly-m-ABA-OMe (1), where both N- and C-terminus are protected, self-assembles to a supramolecular helical structure, whereas the pseudopeptide Boc-Gly-m-ABA-OH (2) with free -CO2H at the C-terminus produces molecular staircase through self-assembly. Again the terminally unprotected pseudopeptide +NH3-Gly-m-ABA-CO2- (3) aggregates to a water mediated supramolecular β-sheet structure stabilized by intermolecular hydrogen bonds and p-p interactions. The study reveals that the terminally modified Gly-m-ABA generates various kinds of self-assembling building blocks that can fabricate different types of supramolecular architectures such as helix, β-sheet and staircase. [ABSTRACT FROM AUTHOR]

Single crystal X-ray diffraction studies show that the β-turn structure of tetrapeptide I, Boc-Gly-Phe-Aib-Leu-OMe (Aib: α-amino isobutyric acid) self-assembles to a supramolecular helix through intermolecular hydrogen bonding along the crystallographic a axis. By contrast the β-turn structure of an isomeric tetrapeptide II, Boc-Gly-Leu-Aib-Phe-OMe self-assembles to a supramolecular β-sheet-like structure via a two-dimensional (a, b axis) intermolecular hydrogen bonding network and π-π interactions. FT-IR studies of the peptides revealed that both of them form intermolecularly hydrogen bonded supramolecular structures in the solid state. Field emission scanning electron micrographs (FE-SEM) of the dried fibrous materials of the peptides show different morphologies, non-twisted filaments in case of peptide I and non-twisted filaments and ribbon-like structures in case of peptide II. [ABSTRACT FROM AUTHOR]

• Novel spiropyranocoumarin and benzofuranyl coumarin scaffolds are synthesized. • Ninhydrin core is employed as the pivotal framework for assembling various phenols. • Spiro pyranocoumarin self-assembled to form sheet-like arrangement. • Benzofuranyl coumarin exhibited helix-like architecture in the crystalline state. • SEM images of spiropyranocoumarin and benzofuranyl coumarin showed flat fibrillar and vesicular morphology. Pyrano and furanocoumarins are oxygen-containing heterocycles frequently found in natural products and biologically active molecules. In the present work, ninhydrin core is employed for the first time as the pivotal framework to construct benzopyrano/furano coumarin skeleton. It has been found that substrates like phenol, p -/ m -cresol, m -methoxyphenol, p -chlorophenol etc. reacted with ninhydrin-4-hydroxycoumarin adduct 3 in AcOH/H 2 SO 4 to furnish a new class of spiropyranocoumarins 5a-f via condensation/cyclization sequence. Under similar conditions, reaction of adduct 3 with 3,5-dihydroxybenzoic acid delivered benzofuranyl coumarin 6 through ring closing/ring opening mechanism. Structures of the synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy. Single crystal X-ray diffraction study revealed that spiropyranocoumarin 5b self-assembled to form sheet-like arrangement. However, benzofuranyl coumarin 6 was found to display helix-like architecture in the crystalline state. Scanning electron microscopy (SEM) images of compound 5b exhibited flat fibrillar morphology, whereas compound 6 revealed formation of vesicular structure. These types of small heterocyclic molecules are decent candidates for producing promising soft materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• New isoquinoline-based compounds were synthesized from readily available ninhydrin. • X-ray diffraction analysis indicated that compound 1 self-assembled to form zipper architecture, while compound 4 displays helical arrangement. • The molecular interactions were explored using the Hirshfeld surface analysis. • SEM study revealed that compound 1 forms vesicular structure, whereas structurally analogous compounds 3 and 4 exhibit fibrillar morphology. Isoquinoline skeletons are ubiquitous in natural products and pharmaceuticals with broad range of biological activity. In the present work, novel isoquinoline compounds are synthesized via the insertion of suitable nucleophile into the ninhydrin core. The reaction of ninhydrin with acetamide in refluxing AcOH afforded indanedione linked isoquinoline derivative 1. On the other hand, treatment of ninhydrin-4-methoxyphenol adduct 2 with ortho phenylenediamine in EtOH/AcOH led to the formation of isoquinoline fused benzimidazole scaffold 3. In DMSO‑ d 6 medium, compound 3 get oxidized to the corresponding isoquinolinone form 4. Single crystal X-ray diffraction study revealed that isoquinoline derivative 1 self-assembled to form zipper arrangement. Interestingly, fused isoquinoline scaffold 4 was found to display supramolecular helical arrangement in the crystalline state. The role of weak intermolecular interactions for development of supramolecular structure has been analysed and quatified using Hirshfeld surface analysis. The scanning electron microscopy (SEM) images of compound 1 show the formation of vesicular structure, whereas structurally analogous compounds 3 and 4 exhibit fibrilllar morphology. [Display omitted] [ABSTRACT FROM AUTHOR]

• Potential of ninhydrin derivatives for tailoring diverse supramolecular architectures is unveiled. • Solid state structures of ninhydrin-acetamide adduct, ninhydrin- p -cresol adduct and N-inserted ninhydrin derivative are analyzed. • First cocrystal of ninhydrin family with 2-aminopyridine is disclosed. • SEM images indicate the surface morphology is greatly influenced by substitution of ninhydrin core. The present work discloses the self-assembly behaviour of differently substituted ninhydrin-based compounds in the solid state for the first time. Ninhydrin core with tunable functionalities generates varied noncovalent interactions leading to different supramolecular assembly. Single crystal X-ray diffraction study revealed that, ninhydrin-acetamide adduct 1 self-assembled to form corrugated sheet structure, whereas ninhydrin- p -cresol adduct 2 (cis dihydroxy hemiketal) containing water of crystallization was found to form water-mediated supramolecular helical architecture. On the other hand, easily achievable N-inserted ninhydrin derivative 3 derived from adduct 2 and o -aminophenol adopted helical arrangement in the crystalline state. Interestingly, novel cocrystal 4 obtained from adduct 2 was found to display helical motif through well directed hydrogen bonding with 2-aminopyridine. The supramolecular diversity arising due to the change in substitution of ninhydrin core structure was also reflected in scanning electron microscopy images. Image, graphical abstract [ABSTRACT FROM AUTHOR]