Modulation of hydrophilicity inside the cavity of molecular rectangles self-assembled under ambient conditions

Three molecular rectangles differing in the flexible methylene chain length show varied hydrophilicity inside their cavities.

Isolation and Structure-Activity Relationship of Subergorgic Acid and Synthesis of Its Derivatives as Antifouling Agent

In this study, as part of our continuous search for environmentally-friendly antifoulants from natural resources, subergorgic acid (SA) was identified from the gorgonian coral Subergorgia suberosa, demonstrating non-toxic, significant inhibitory effects (EC50 1.25 μg/mL, LC50 > 25 μg/mL) against the settlement of Balanus amphitrite. To further explore the bioactive functional groups of SA and synthesize more potent antifouling compounds based on the lead SA, the structure-activity relationships of SA were studied, followed by rational design and synthesis of two series of SA derivatives (one being benzyl esters of SA and another being SA derivatives containing methylene chains of various lengths). Our results indicated that (1) both the double bond and ketone carbonyl are essential elements responsible for the antifouling effect of SA, while the acid group is not absolutely necessary for maintaining the antifouling effect; (2) all benzyl esters of SA displayed good antifouling effects (EC50 ranged from 0.30 to 2.50 μg/mL) with the most potent compound being 5 (EC50 0.30 μg/mL, LC50 > 25 μg/mL), which was over four-fold more potent than SA; and (3) the introduction of a methylene chain into SA reduces the antifouling potency while the length of the methylene chain may differently influence the antifouling effect, depending on the functional group at the opposite site of the methylene chain. Not only has this study successfully revealed the bioactive functional groups of SA, contributing to the mechanism of SA against the settlement of B. amphitrite, but it has also resulted in the identification of a more potent compound 5, which might represent a non-toxic, high-efficiency antifoulant.

Methylene chain ruler for evaluating the regioselectivity of a substrate-recognising oxidation catalyst

We designed and synthesised Ru porphyrin 1a as an oxidation catalyst with substrate recognition sites. The 1a catalysed oxidation of substrate 7 selectively oxidised the central position of the methylene chain, affording ketone 8 as the major product.

Length Matters: One Additional Methylene Group in a Reactant is Able to Affect the Reactivity Pattern and Significantly Increase the Product Yield

The outcome of the nucleophilic opening of 3-O-benzoyl-β-d-arabinofuranose 1,2,5-orthobenzoate with 4-(ω-chloroalkoxy)phenols (SnCl4, CH2Cl2, –25 °C) unusually strongly depends on the length of the methylene chain of the nucleophile. The presence of one extra methylene group in the molecule of 4-(3-chloropropoxy)phenol [as compared to 4-(2-chloroetoxy)phenol] results in four-fold reduction in the reaction time and five-fold increase in the yield of a selectively protected monosaccharide glycoside with a hydroxy group at C-5, which is a valuable building block for the synthesis of oligoarabinofuranosides related to mycobacterial arabinans. Possible reasons and consequences of this finding are discussed.

Preparation of aliphatic polypyromellitimide particles by polycondensation of nylon-salt-type monomers derived from aliphatic diamines with diethyl pyromellitate in ethylene glycol

Polycondensations of nylon-salt-type monomers composed with diethyl pyromellitate and aliphatic diamines with various methylene lengths were performed at 130 °C in ethylene glycol to afford flower-like particles. Before the polycondensation, the salt monomer solution was homogenous. As the polycondensation proceeded, the solution became turbid and polyimide particles grew to around 15 µm in 8 h. Further polycondensation broke the particles into small pieces. The polyimide particles showed the distinctive odd-even effect of the methylene chain of diamine in both inherent viscosity and crystallinity. The polyimide particles using diamine with even-methylene length had higher crystallinity and lower inherent viscosity than those using diamine with odd-methylene length.