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Abstract β‐lactams are a chemically diverse group of molecules with a wide range of biological activities. Having recently observed curious trends in²J_HHcoupling values in studies on this structural class, we sought to obtain a more comprehensive understanding of these diagnostic NMR parameters, specifically interrogating¹J_CH,²J_CH, and²J_HH, to differentiate 3‐ and 4‐monosubstituted β‐lactams. Further investigation using computational chemistry methods was employed to explore the geometric and electronic origins for the observed and calculated differences between the two substitution patterns. 

Abstract A great diversity of crustacean zooplankton found in inland and coastal waters produce embryos that settle into bottom sediments to form an egg bank. Embryos from these banks can remain dormant for centuries, creating a reservoir of genetic diversity. A large body of literature describes the ecological and evolutionary importance of zooplankton egg banks. However, literature on the physiological traits behind dormancy in crustacean zooplankton are limited. Most data on the physiology of dormancy comes from research on one species of anostracan, the brine shrimp,Artemia franciscana. Anoxia-induced dormancy in this species is facilitated by a profound and reversible acidification of the intracellular space. This acidification is accompanied by a reversible depletion of adenosine triphosphate (ATP). The present study demonstrates that acidification of the intracellular space also occurs in concert with a depletion of nucleoside triphosphates (NTPs) in the Antarctic copepod,Boeckella poppei. LikeA. franciscana, the depletion of NTPs and acidification are rapidly reversed during aerobic recovery inB. poppei. These data provide the first comparative evidence that extreme dormancy under anoxia in crustacean zooplankton is associated with intracellular acidification and an ability to recover from the depletion of ATP. 

NMR pulse sequences visualizing 1 J CC and n J CC bond connectivity via an intermediate state of 13 C– 13 C double-quantum coherence and 1 H detection are an indispensable tool to solve small-molecule structures at the natural abundance level of 13 C. A longstanding issue with these experiments set up to display 2D spectra with single-quantum frequencies is that in addition to the 1 H– 13 C– 13 C correlations of interest, appearance of HSQC-type artifacts can complicate analysis and obscure J CC connectivities. The origin of these artifacts is described and remedies for their suppression are introduced. They include refocusing of 1 J CH couplings prior to creation of 13 C– 13 C double-quantum coherence, which is known to enhance sensitivity by reducing loss into zero-quantum coherence for pairs of two protonated 13 C. 

Abstract Carbon‐centered radicals stabilized by adjacent boron atoms are underexplored reaction intermediates in organic synthesis. This study reports the development of vinyl cyclopropyl diborons (VCPDBs) as a versatile source of previously unknown homoallylic α,α‐diboryl radicals via thiyl radical catalyzed diboron‐directed ring opening. These diboryl stabilized radicals underwent smooth [3+2] cycloaddition with a variety of olefins to provide diboryl cyclopentanes in good to excellent diastereoselectivity. In contrast to thetrans‐diastereoselectivity observed with most of the dicarbonyl activated VCPs, the cycloaddition of VCPDBs showed a remarkable preference for formation ofcis‐cyclopentane diastereomer which was confirmed by quantitative NOE and 2D NOESY studies. Thecis‐stereochemistry of cyclopentane products enabled a concise intramolecular Heck reaction approach to rare tricyclic cyclopentanoid framework containing the diboron group. The mild reaction conditions also allowed a one‐pot VCP ring‐opening, cycloaddition‐oxidation sequence to afford disubstituted cyclopentanones. Control experiments and DFT analysis of reaction mechanism support a radical mediated pathway and provide a rationale for the observed diastereoselectivity. To the authors’ knowledge, these are the first examples of the use of geminal diboryl group as an activator of VCP ring opening and cycloaddition reaction of α‐boryl radicals.