Gelatin-Tannin-Based Greener Binder Technology for Stone Shot and Stone Wool Materials: A Detailed Study.

The detailed study presented herein of gelatins modified with tannins as greener binder systems for stone wool and related materials has unveiled a versatile technology that offers a wide range of possibilities for tailor-making properties toward various application areas. Thus, high unaged and aged mechanical strengths in combination with low water solubilities may generally be obtained from the use of gelatins with higher gel strength (and hence, generally, higher molecular weights), low-to-mid range tannin addition levels (3-20%), alkali metal hydroxides for pH adjustment, and final pH in the range 8-9. Comparatively low water uptake properties may be obtained using higher gel strength type A gelatins, lower tannin addition levels, alkali metal hydroxides for pH adjustment, and lower final pH. Even lower water uptake properties may then be obtained using Ca(OH)2 in place of alkali metal hydroxides. If desired, higher water uptakes may be obtained using type B gelatins (or lower gel strength gelatins in general), higher tannin addition levels, and higher final pH. Mechanistic studies indicated that the optimal modification of gelatin with the tannin component occurs via several pathways.

N-Alkylated Aromatic Poly- and Oligoamides.

N-alkylated aromatic poly- and oligoamides are a particular class of abiotic foldamers that is deprived of the capability of forming intramolecular hydrogen-bonding networks to stabilize their tri-dimensional structure. The alkylation of the backbone amide nitrogen atoms greatly increases the chemical diversity accessible for aromatic poly- and oligoamides. However, the nature and the conformational preferences of the N,N-disubstituted amides profoundly modify the folding properties of these aromatic poly- and oligoamides. In this Review, representative members of this class of aromatic poly- and oligoamides will be highlighted, among them N-alkylated phenylene terephthalamides, benzanilides, pyridylamides, and aminomethyl benzamide oligomers. The principal synthetic pathways to the main classes of N-alkylated aromatic polyamides with narrow to broad molecular-weight distribution, or oligoamides with specific sequences, will be detailed and their foldameric properties will be discussed. The Review will end by describing the few applications reported to date and future prospects for the field.

Topologically Diverse Shapes Accessible by Modular Design of Arylopeptoid Macrocycles.

N-Substituted aromatic cyclooligoamides composed of different combinations of ortho-, meta-, and/or para-arylopeptoid residues carrying methoxyethyl side chains have been efficiently synthesized by macrocyclization of the corresponding linear oligomers. The study of the architectures of these macrocycles in solution and solid state has revealed that tetracyclic arylopeptoids adopt sequence-dependent shapes with different backbone amide conformations and side-chain orientations. Remarkably, despite the absence of intramolecular H-bonding ability, some of these arylopeptoid macrocycles show well-defined architectures in solution.

Macrocyclic arylopeptoids--a novel type of cyclic N-alkylated aromatic oligoamides forming nanotubular assemblies.

The head-to-tail conversion of linear arylopeptoids (oligomeric N-substituted aminomethyl benzamides) into the derived novel macrocycles has enabled the first X-ray structures of arylopeptoid constructs and the identification of well-defined architectures in solution.

Discovery of new PPARγ agonists based on arylopeptoids.

In this study we present the design, synthesis and biological evaluation of a small, first-generation library of small molecule aromatic amides based on the arylopeptoid skeleton. The compounds were efficiently synthesized using a highly convenient submonomer solid-phase methodology which potentially allows for access to great product diversity. The synthesized compounds were tested for their ability to activate peroxisome proliferator-activated receptors (PPARs) and they all acted as PPARγ agonists in the µM range spanning from 2.5- to 14.7-fold activation of the receptor. This is the first discovery of bioactive molecules based on the arylopeptoid architecture.

Cyclic α,ß-tetrapeptoids: sequence-dependent cyclization and conformational preference.

The presence of at least one N-Cα branched side chain is crucial for successful cyclization of α,ß-tetrapeptoids. The ctct amide sequence revealed in the crystal structure of the 14-membered cyclotetrapeptoid 8 is also the most populated conformation in solution and is reminiscent of the predominant amide arrangement of the 12-membered cyclic tetrapeptides (CTPs).

Efficient and versatile COMU-mediated solid-phase submonomer synthesis of arylopeptoids (oligomeric N-substituted aminomethyl benzamides).

The development of a highly efficient methodology for solid-phase synthesis of para- and meta-arylopeptoids (oligomeric N-substituted aminomethyl benzamides) with free acids or free amides at the C-terminus is described. The arylopeptoids were synthesised by means of a convenient submonomer protocol in which the arylopeptoid residues were created in an iterative manner on the growing chain using an acylation-substitution cycle. The uronium salt COMU was found to be the most efficient reagent for ensuring fast and clean couplings of the benzoic acid building blocks.

Cyclic α,ß-peptoid octamers with differing side chain patterns: synthesis and conformational investigation.

The solution-phase synthesis and cyclisation of three α,ß-peptoid octamers with differing side chain patterns is reported. One of these, compound C, showed a significantly greater resolution by NMR relative to the other two structurally related octamers. This observation was studied in detail by circular dichroism at a synchrotron light source to facilitate the correlation between the side chain patterns and conformational preference of these three peptoids. The X-ray crystal structure of cyclic octamer C, the first high-resolution structure for the α,ß-peptoid backbone, was also obtained from methanol. Combined solid- and solution-phase studies allowed the identification of the N-2-(benzyloxy)ethyl side chain on the ß-residue of the heterogeneous backbone as a key structural feature driving the increased conformational stability for octamer C.

Convenient solution-phase synthesis and conformational studies of novel linear and cyclic alpha,beta-alternating peptoids.

The synthesis of a novel family of peptidomimetics composed of linear and cyclic alpha,beta-alternating peptoids is described. Oligomers consisting of up to six peptoid residues (n = 1-3) were synthesized on large scale with use of an efficient iterative solution-phase method and longer oligomers (n = 4, 5) were obtained by the coupling of appropriately protected shorter oligomers. Preliminary conformational studies of these hybrid peptoids are reported.

Passerini reaction-amine deprotection-acyl migration peptide assembly: efficient formal synthesis of cyclotheonamide C.

A short, convergent, formal total synthesis of cyclotheonamide C is described. The key linear pentapeptide intermediate is assembled at the same time as the elaboration of the alpha-hydroxyhomoarginine (H-hArg) residue via a three-component Passerini reaction-amine deprotection-O,N-acyl migration strategy.

Rapid assembly of the polyhydroxylated beta-amino acid constituents of microsclerodermins C, D, and E.

A very short and efficient synthesis of protected derivatives of APTO and AETD, the complex polyhydroxylated beta-amino acid residues present in microsclerodermins C, D, and E, is described. The targets are obtained in only five steps, in 23% and 16% overall yields, respectively. The key transformation involves the completely diastereoselective two-carbon homologation of appropriately selected intermediate chiral sulfinimines.

Expedient total synthesis of pyrrothine natural products and analogs.

This paper describes an expedient and straightforward total synthesis of the two pyrrothine natural products holomycin (7 steps, 11% overall) and xenorhabdin I (7 steps, 11% overall) and analogs thereof via a common late-stage intermediate. The pathway proceeds via the pyrrothine hydrochloride intermediate (6 steps, 17% overall) which also gave access to very fast synthesis of analogs as demonstrated by the synthesis of , and (7 steps, 11-12% overall).

Copper(I) mediated cross-coupling of amino acid derived organozinc reagents with acid chlorides.

This paper describes the development of a straightforward experimental protocol for copper-mediated cross-coupling of amino acid derived beta-amido-alkylzinc iodides 1 and 3 with a range of acid chlorides. The present method uses CuCN.2LiCl as the copper source and for organozinc reagent 1 the methodology appears to be limited to reaction with more stable acid chlorides, providing the desired products in moderate yields. When applied to organozinc reagent 3, however, the protocol is more general and provides the products in good yields in all but one of the cases tested.

Total synthesis of pinnamine and anatoxin-a via a common intermediate. A caveat on the anatoxin-a endgame.

[reaction: see text] This paper describes the total synthesis of the naturally occurring alkaloids pinnamine (1) and anatoxin-a (2) from a common enantiomerically pure intermediate (7) easily available from pyroglutamic acid. The synthesis of enantiopure pinnamine proceeded in 10 steps and 4.8% overall yield, and the route was flexible enough to allow stereocontrolled access to a non-natural congener (5-epi-pinnamine) of the natural product. Intramolecular reaction of an N-acyl iminium ion was a key step in the synthesis of both pinnamine and anatoxin-a. However, in stark contrast to literature precedent, complete racemization was observed during the reaction of the N-acyliminium ion leading to the latter alkaloid.

Synthesis of furanone-based natural product analogues with quorum sensing antagonist activity.

The synthesis of 5- and 3-(1'-hydroxyalkyl)-substituted 5H-furan-2-ones 4a-d and 8a-d as well as 5-alkylidene-5H-furan-2-ones 5a-d is described. A study of the structure-activity relationship of these furanone-based natural product analogues towards two different quorum sensing systems is reported. Although the synthesized compounds are not as potent quorum sensing inhibitors as some natural counterparts and a synthetic analogue hereof, interesting structure-activity relationships are seen.