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While significant progress has been made in understanding global carbon (C) cycling, the mechanisms regulating belowground C fluxes and storage are still uncertain. New molecular technologies have the power to elucidate these processes, yet we have no widespread standardized implementation of molecular techniques. To address this gap, we introduce the Molecular Observation Network (MONet), a decadal vision from the Environmental Molecular Sciences Laboratory (EMSL), to develop a national network for understanding the molecular composition, physical structure, and hydraulic and biological properties of soil and water. These data are essential for advancing the next generation of multiscale Earth systems models. In this paper, we discuss the 1000 Soils Pilot for MONet, including a description of standardized sampling materials and protocols and a use case to highlight the utility of molecular-level and microstructural measurements for assessing the impacts of wildfire on soil. While the 1000 Soils Pilot generated a plethora of data, we focus on assessments of soil organic matter (SOM) chemistry via Fourier-transform ion cyclotron resonance-mass spectrometry and microstructural properties via X-ray computed tomography to highlight the effects of recent fire history in forested ecosystems on belowground C cycling. We observed decreases in soil respiration, microbial biomass, and potential enzyme activity in soils with high frequency burns. Additionally, the nominal oxidation state of carbon in SOM increased with burn frequency in surface soils. This results in a quantifiable shift in the molecular signature of SOM and shows that wildfire may result in oxidation of SOM and structural changes to soil pore networks that persist into deeper soils.

Electrolysis flow reactors based on the filter-press architecture of redox flow batteries have proven to be effective and scalable toward the production of commercially relevant, pharmaceutical qua...

A total synthesis of the aglycone of IB-00208 was accomplished in 22 steps using a newly developed approach towards polycyclic 1,4-dioxygenated xanthones from benzocyclobutenones. The generality of this entry to xanthones was initially established on several model systems before it was successfully applied to the construction of the hexacyclic core of the natural product. A new and potentially general approach towards angularly-fused benzocyclobutenones using ring-closing metathesis (RCM) was also developed.

Hexacyclic xanthone natural products such as IB-00208 present a formidable challenge in organic synthesis. A new approach to polycyclic 1,4-dioxygenated xanthones from benzocyclobutenones has been developed and applied to the first total synthesis of the aglycone of IB-00208. The 22-step synthesis features an acetylide stitching process that joins an aryl aldehyde with an angularly fused benzocyclobutenone, which was prepared by a ring-closing metathesis reaction. The resulting acetylenic benzocyclobutenone diol underwent a Moore rearrangement to give an intermediate that was further elaborated to the aglycone of IB-00208 as a mixture of hydroquinone–quinone tautomers.

We report the first total synthesis of the complex C-aryl glycoside isokidamycin, the epimer of the naturally-occurring pluramycin antibiotic kidamycin. The synthesis features a highly efficientDiels-Alder reaction between a substituted naphthyne and a glycosylatedfuran to form the anthracene core bearing a pendant angolosamine C-glycoside. The regiochemical outcome of the Diels-Alder reaction was controlled by employing a disposable silicon-tether to link the reactive napthyne and the glycosyl furan, rendering the cycloaddition intramolecular. The benzopyranone moietyof the aromatic nucleus was appended by cyclization of a functionalized vinylogous amide onto an advanced anthrol intermediate. The vancosamine amino glycoside was introduced by an O→C-glycoside rearrangement that produced the β-anomer. Subsequent refunctionalizations then led to isokidamycin.

A two-step procedure is described to access 3-alkoxycyclobutanones from chloroacetyl chloride utilizing a step-wise [2+2] ketene cycloaddition followed by catalytic hydrogenation to reduce the α-chlorine in a single reaction sequence. The resulting cyclobutanones can be readily converted into a variety of cis or trans-1,3-disubstituted aminocyclobutanols and cyclobutanediols.

A Kumada cross-coupling reaction involving organomagnesium reagents and (3-methylthio-2-azaallyl)stannanes with a Ni(0) catalyst provided cyclic nonstabilized (2-azaallyl)stannanes in moderate to good yields. Primary alkyl, aryl, and allylic organomagnesium reagents can be used as the cross-coupling partner. In general, NiCl(2)dppp in toluene at room temperature provided the shortest reaction times and most consistent yields. The azomethine ylides and 2-azaallyllithium species derived from these stannanes were shown to undergo efficient [3 + 2] cycloaddition reactions to provide azabicyclo[n.2.1]alkanes as the endo cycloadducts. These cycloadducts were found to be useful as starting materials for further elaboration into aza-bridged bicyclic natural and unnatural products of biological interest. Although cyclic 2-azaallyllithium species have been generated previously, this work reports the first generation and cycloaddition of entirely nonstabilized 2-azaallyllithium species. In addition a novel extension of the Kumada coupling was developed to allow for the preparation of the cyclic (2-azaallyl)stannanes, which are precursors to the nonstabilized 2-azaallyllithium species.

[reaction: see text] The total synthesis of (+)-cocaine is described. An extension of the recently reported proline catalyzed intramolecular enol-exo-aldol reaction to a meso-dialdehyde provided the tropane ring skeleton directly with good enantiomeric excess. The meso-dialdehyde was prepared using a 2-azaallyllithium [3 + 2] cycloaddition to generate a cis-2,5-disubstituted pyrrolidine. Overall, the synthesis proceeded in 6.5% yield and 86% ee over 14 linear steps starting from commercially available 3-benzyloxy-1-propanol.

The temperature-dependent formation of a remarkably stable enol from the reaction of EtMgBr with a 1,2-diester was accidentally discovered. This compound was spectroscopically characterized (1H and 13C NMR, IR), and both methyl carbonate and trimethylsilyl ether derivatives were prepared. A mechanism for the selective formation of the stable enol ester and its corresponding keto form was suggested, and the kinetic stability of the enol was also documented. The generality of the observation of such a stable enol ester was demonstrated with the use of other Grignard reagents, and also other 1,2-diesters. The reaction of EtMgBr with a series of 1,2-amide esters also produced stable enol amides. The remarkable stability of the enol esters was attributed to the steric hindrance present in the aryl ester moiety of these compounds, and further studies will address the origin of this effect.

A three-step procedure to access fused pyridines has been developed utilizing inexpensive amino acids and alkenols to form the key oxazole precursors. Yields are good to excellent and provide a rapid and inexpensive route to a range of pharmacologically and biologically valuable fused pyridines with difficult to access substitution patterns.

A three-step procedure to access fused pyridines has been developed utilizing inexpensive amino acids and alkenols to form the key oxazole precursors. Yields are good to excellent and provide a rapid and inexpensive route to a range of pharmacologically and biologically valuable fused pyridines with difficult to access substitution patterns.

3-Alkoxycyclobutanones such as (IV) are obtained from [2 + 2] cycloaddition of alkyl vinyl ether and chloroketene followed by hydrogenolytic dechlorination.

The synthesis of isokidamycin, which represents the first total synthesis of a bis-C-aryl glycoside natural product in the pluramycin family, has been completed. The synthesis features the use of a silicon tether as a disposable regiocontrol element in an intramolecular Diels-Alder reaction between a substituted naphthyne and a glycosyl furan and a subsequent O → C-glycoside rearrangement.

2-Azaallyllithium species [R(1)CH(-)N=C(X)R(2)Li(+), where R(1) and R(2) are alkyl and X = OMe] were generated by tin-lithium exchange of (2-azaallyl)stannanes and underwent [pi4s+pi2s] and [pi6s+pi4s] cycloadditions with cyclic dienes and trienes, respectively, to generate novel bridged azabicyclic compounds in a highly diastereoselective endo fashion. The periselectivity using cycloheptatriene was modest, producing a 1:1 mixture of [pi6s+pi4s] and [pi4s+pi2s] adducts. The reactions of 2-azaallyllithium species with dienes proceeded by a [pi4s+pi2s] pathway. The cycloadducts derived from cyclic 2-azaallyllithium species possess the 7-azabicyclo[2.2.1]heptane (tropane) or 8-azabicyclo[3.2.1]octane ring system and have been elaborated into cocaine-like analogues.

[reaction: see text] Transmetalation of tin-bearing cyclic imidates gave 2-azaallyllithiums that underwent [pi6s + pi4s] cycloadditions with cycloheptatriene to produce tricyclic adducts, which may be useful as analogs of cocaine. The peri- and stereoselectivity of this process are discussed.