1. Ipso Nitration of Aryl Boronic Acids Using Fuming Nitric Acid
James I Murray, Maria V Silva Elipe, Kyle D Baucom, Derek B Brown, Kyle Quasdorf, Seb Caille J Org Chem. 2022 Feb 18;87(4):1977-1985. doi: 10.1021/acs.joc.1c00886. Epub 2021 Jun 8.
The ipso nitration of aryl boronic acid derivatives has been developed using fuming nitric acid as the nitrating agent. This facile procedure provides efficient and chemoselective access to a variety of aromatic nitro compounds. While several activating agents and nitro sources have been reported in the literature for this synthetically useful transformation, this report demonstrates that these processes likely generate a common active reagent, anhydrous HNO3. Kinetic and mechanistic studies have revealed that the reaction order in HNO3 is >2 and indicate that the ·NO2 radical is the active species.
2. The Stephan Curve revisited
William H Bowen Odontology. 2013 Jan;101(1):2-8. doi: 10.1007/s10266-012-0092-z. Epub 2012 Dec 6.
The Stephan Curve has played a dominant role in caries research over the past several decades. What is so remarkable about the Stephan Curve is the plethora of interactions it illustrates and yet acid production remains the dominant focus. Using sophisticated technology, it is possible to measure pH changes in plaque; however, these observations may carry a false sense of accuracy. Recent observations have shown that there may be multiple pH values within the plaque matrix, thus emphasizing the importance of the milieu within which acid is formed. Although acid production is indeed the immediate proximate cause of tooth dissolution, the influence of alkali production within plaque has received relative scant attention. Excessive reliance on Stephan Curve leads to describing foods as "safe" if they do not lower the pH below the so-called "critical pH" at which point it is postulated enamel dissolves. Acid production is just one of many biological processes that occur within plaque when exposed to sugar. Exploration of methods to enhance alkali production could produce rich research dividends.
3. 2-epi-botcinin A and 3-O-acetylbotcineric acid from Botrytis cinerea
Emi Sakuno, Hiroko Tani, Hiromitsu Nakajima Biosci Biotechnol Biochem. 2007 Oct;71(10):2592-5. doi: 10.1271/bbb.70334. Epub 2007 Oct 7.
Two metabolites, 2-epi-botcinin A and 3-O-acetylbotcineric acid, were isolated from Botrytis cinerea (AEM211). The former compound was new, and the latter was known but structurally revised by us. In a test for antifungal activity against Magnaporthe grisea, a pathogen of rice blast disease, 2-epi-botcinin A was 8 times less active than botcinin A (MIC 100 microM), and the MIC value for 3-O-acetylbotcineric acid being 100 microM.
