Substituent Effect in 2‑Benzoylmethylenequinoline Difluoroborates Exhibiting Through-Space Couplings. Multinuclear Magnetic Resonance, X‑ray Diffraction, and Computational Study

The series of nine 2-benzoylmethylenequinoline difluoroborates have been synthesized and characterized by multinuclear magnetic resonance, X-ray diffraction (XRD), and computational methods. The through-space spin–spin couplings between ¹⁹F and ¹H/¹³C nuclei have been observed in solution. The NMR chemical shifts have been correlated to the Hammett substituent constants. The crystal structures of six compounds have been solved by XRD. For two derivatives the X-ray wave function refinement was performed to evaluate the character of bonds in the NBF₂O moiety by topological and integrated bond descriptors

Joseph Bosworth, Little Horwood Vicarage, near Winslow, Buckinghamshire, to Sir James Edward Smith, Norwich, [Norfolk]

Congratulates Smith on his return to health and goes on to praise Smith's "most valuable and learned works on botany", the women in his family are especially delighted with the "The English Flora" and Smith's "precision" compares favourably to the "vapid conversations and trite introductions to botany that have lately appeared". For the sake of women readers suggests that in his "Introduction to Botany" Smith accentuates the "peculiar" words so as to aid pronunciation

Discovery of a Pederin Family Compound in a Nonsymbiotic Bloom-Forming Cyanobacterium

The pederin family includes a number of bioactive compounds isolated from symbiotic organisms of diverse evolutionary origin. Pederin is linked to beetle-induced dermatitis in humans, and pederin family members possess potent antitumor activity caused by selective inhibition of the eukaryotic ribosome. Their biosynthesis is accomplished by a polyketide/nonribosomal peptide synthetase machinery employing an unusual <i>trans-</i>acyltransferase mechanism. Here, we report a novel pederin type compound, cusperin, from the free-living cyanobacterium <i>Cuspidothrix issatschenkoi</i> (earlier <i>Aphanizomenon</i>). The chemical structure of cusperin is similar to that of nosperin recently isolated from the lichen cyanobiont <i>Nostoc</i> sharing the tehrahydropyran moiety and major part of the linear backbone. However, the cusperin molecule is extended by a glycine residue and lacks one hydroxyl substituent. Pederins were previously thought to be exclusive to symbiotic relationships. However, <i>C. issatschenkoi</i> is a nonsymbiotic planktonic organism and a frequent component of toxic water blooms. Cusperin is devoid of the cytotoxic activity reported for other pederin family members. Hence, our findings raise questions about the role of pederin analogues in cyanobacteria and broaden the knowledge of ecological distribution of this group of polyketides