Microchemical investigation of medicinal plants. V

Summary The spectral analysis of the yellow compound isolated from the seeds ofC. Bignonioides was carried out to further investigate its structure. The presence of two methoxyl groups, two hydroxyl groups, and an ,-unsaturated carbonyl is firmly established. It is not possible at this time to substantially confirm whether the carbonyl is an aromatic aldehyde or a six-membered ring ketone. The molecular formula, C₁₇H₁₄O₆ (11 sites of unsaturation and/or rings), is established. The compound does not contain any methyl or methylene groups. The location of one methoxyl and one hydroxyl closer to an electronegative group (i. e. a furanoic oxygen) is indicated. The hydroxyl groups are not located ortho to the carbonyl.The compound has a polynuclear aromatic structure. The evidence indicates one ring is 1,2,3,4-tetra substituted. Another ring may be 1,2,3,5-tetrasubstituted or 1,3,5-trisubstituted. A heteroaromatic group (e. g. furan) may also be present.Further work is in progress to elucidate the structure of the compound.

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Zusammenfassung Die Spektralanalyse der gelben, aus Catalpasamen isolierten Verbindung wurde zwecks weiterer Untersuchung ihrer Struktur durchgeführt. Die Anwesenheit zweier Methoxylgruppen, zweier Hydroxylgruppen und einer,-ungesättigten Carbonylgruppe wurde sichergestellt. Bis jetzt ist nicht zu entscheiden, ob letztere einer aromatischen Aldehydgruppe oder einem sechsgliedrigen cyklischen Keton zugehört. Die Summenformel C₁₇H₁₄O₆ mit elf ungesättigten Bindungen und/oder Ringen wurde nachgewiesen. Die Verbindung enthält keine Methyl- oder Methylengruppen. Die Lokalisation einer Methoxyl- und einer Hydroxylgruppe in der Nähe einer elektronegativen Gruppe (das heißt, eines furanoiden Sauerstoffs) ist erkennbar. Die Hydroxylgruppen stehen zur Carbonylgruppe nicht ino-Stellung.Die Verbindung hat polynukleare aromatische Struktur. Ein Ring ist in den Stellungen 1, 2, 3 und 4 substituiert, ein weiterer in den Stellungen 1, 2, 3 und 5 oder nur in 1, 3 und 5. Eine heterocyklische Gruppe (z. B. Furan) dürfte anwesend sein. Die Untersuchungen werden fortgesetzt.

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For Part IV see Mikrcohim. Acta [Wien]1968, 1085.     

Synthesis and protein degradation capacity of photoactivated enediynes

[structure: see text] The viability of proteins as targets of thermally and photoactivated enediynes has been confirmed at the molecular level. Model studies using a labeled substrate confirmed the efficacy of atom transfer from diyl radicals produced from enediynes to form captodatively stabilized carbon centered aminoacyl radicals, which then undergo either fragmentation or dimerization. To exploit this finding, a family of enediynes was developed using an intramolecular coupling strategy. Derivatives were prepared and used to target specific proteins, showing good correlation between affinity and photoinduced protein degrading activity. The findings have potential applications in the design of artificial chemical proteases and add to our understanding of the mechanism of action of the clinically important enediyne antitumor antibiotics.     

Long descending cervical propriospinal neurons differ from thoracic propriospinal neurons in response to low thoracic spinal injury

Background  

Propriospinal neurons, with axonal projections intrinsic to the spinal cord, have shown a greater regenerative response than supraspinal neurons after axotomy due to spinal cord injury (SCI). Our previous work focused on the response of axotomized short thoracic propriospinal (TPS) neurons following a low thoracic SCI (T9 spinal transection or moderate spinal contusion injury) in the rat. The present investigation analyzes the intrinsic response of cervical propriospinal neurons having long descending axons which project into the lumbosacral enlargement, long descending propriospinal tract (LDPT) axons. These neurons also were axotomized by T9 spinal injury in the same animals used in our previous study.     

Electron transfer driven by proton fluctuations in a hydrogen-bonded donor-acceptor assembly

The temperature-isotope dependence of proton-coupled electron transfer (PCET) for a noncovalent molecular dyad is reported. The system consists of an excited-state Zn(II) porphyrin that transfers an electron to a naphthalene diimide acceptor through an amidinium-carboxylate interface. Two different isotope effects are observed for variant temperature regimes. A reverse isotope effect (i.e., kH/kD < 1) is observed as T approaches 120 K (kH/kD = 0.9, 120 K), whereas a normal isotope effect (i.e., kH/kD > 1) is recovered as the temperature is increased (kH/kD = 1.2, 300 K). The transition between these limits is smooth, with a crossover temperature of T approximately 160 K. These observations are in accordance with charge-transfer dynamics that are susceptible to bath-induced fluctuations in the proton coordinate.     

Reaction mechanisms and kinetics for the oxidations of dimethyl sulfide, dimethyl disulfide, and methyl mercaptan by the nitrate radical

This study examines the initial oxidation routes of the three major reduced sulfur compounds (CH(3)SH, CH(3)SCH(3), and CH(3)SSCH(3)) by the nitrate radical using density functional and ab initio methods. Stationary points along each reaction pathway are examined using different levels of theory and basis sets to ensure the convergence of the results. Kinetics calculations follow on the determined reaction pathways to obtain the rate constants. This study shows that sulfur compounds exhibit a general trend of hydrogen abstraction following the formation of an initial sulfur-nitrate complex. The results are in agreement with experimental work on CH(3)SCH(3) and CH(3)SH, while refuting a proposal of several previous studies that oxygen addition is the dominant oxidation pathway in the case of CH(3)SSCH(3). The rate constants obtained from kinetics calculations are consistent with experimental findings and exhibit negative temperature dependence. Overall, this study confirms the importance of nitrate in the oxidation of reduced sulfur compounds in the atmosphere.