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Answers to Problems Introduction to Spectroscopy, 3rd edition
Monatshefte fuer Chemie/Chemical Monthly
Chemistry of Natural Compounds
Two new clerodanolides — salvicinolide and salvicinolin — have been isolated from the epigeal part ofPulicaria salviifolia Bge inMem (fam. Compositae). Their structures have been established by an investigation of their spectral and physicochemical characteristics. It has been found that salvicinolide is capable of cyclizing at the C-6 and C-19 carbon atoms with the formation of a second lactone ring. The structure of 6α-hydroxy-19-carboxy-trans-clero-3,13-dien-15-olide is proposed for salvicinolide, and 6α,13-dihydroxy-19-carboxy-rans-cleroda-3,13-diene for salvicinolin.
"Abstract A series of variously substituted N-methylpiperidin- 4-one-O-benzyloximes were synthesized by three different methods. Among them, the direct conversion of 2,6-diarylpiperidin-4-ones into the corresponding oxime ethers (method A) was proved to be better than the other two methods in the sense of good yield, convenience, easy work-up and quick reaction time. All the synthesized compounds are characterized by IR, Mass and NMR (1H NMR, 13C NMR, 1H-1H COSY, 1H-13C COSY and HMBC) spectral studies. The conformational preference of the synthesized oxime ethers with/without alkyl and aryl substituents at C-3/C-5 and C-2/C-6 is discussed using the spectral data. The observed chemical shifts and coupling constants suggest that the synthesized oxime ethers adopt chair conformation with equatorial orientation of all the substituents, whereas 1-methyl-3-isopropyl-2,6-diphenylpiperidin- 4-one-O-benzyloxime also exists in boat conformation. Based on the NMR data, the effects of oximination on ring carbons and their associated protons and alkyl substituents are discussed. In addition, the effect of NMe group on the 2,6-diarylpiperidin-4-one-O-benzyloximes was also studied."
Organic Magnetic Resonance
Dyes and Pigments
Guido Viscardi , Pierluigi Quagliotto
Inorganica Chimica Acta
Dennis Sardella , Jerry Jasinski
Variously substituted 2,6-diarylpiperidin-4-one O-benzyloximes were synthesized by the direct condensation of the corresponding 2,6- diarylpiperidin-4-ones with O-benzylhydroxylamine hydrochloride. All the synthesized compounds are characterized by IR, Mass and NMR spectral studies. NMR spectral assignments are made unambiguously by their one-dimensional (1H NMR and 13C NMR) and two-dimensional (1H–1H COSY, NOESY, HSQC and HMBC) NMR spectra. All the synthesized compounds are resulted as single isomer, i.e., exclusively E isomer (9–14). The conformational preference of 2,6-diarylpiperidin-4-one oxime ethers with and without alkyl substituents at C-3 and C-5 has also been discussed using the spectral studies. The observed chemical shifts and coupling constants suggest that compounds 8–13 adopt normal chair conformation with equatorial orientation of all the substituents while compound 14 contributes significant boat conformation along with the predominant chair conformation in solution. The effect of oximination on ring carbons, their associated protons, alkyl substituents and ipso carbons are studied. Every proton in the piperidone ring of the oxime ether is observed as distinct signal due to oximination. The order of chemical shift magnitude in compound 8 is H-2a > H-6a > H-5e > H-3e > H-3a > H-5a. For 9–12, the order is H-6a > H-5e > H-2a > H-3a > H-5a, for 13, H-6a > H-2a > H-5e > H-3a > H-5a and for 14, the order is H-2a > H-6a > H-5e > H-3a > H-5a while the 13C chemical shift magnitude for 8–14 due to oximination is C-2 > C-6 > C-3 > C-5.
Five new compounds have been isolated from the fresh fruits of Momordica charantia and their structures elucidated through spectroscopic studies. These include three pentacyclic triterpenes 13-hydroxy-28-methoxy-urs-11-en-3-one (momordicin), 13β,28-epoxy-urs-11-en-3-one (momordicinin), 24-[1′-hydroxy,1′-methyl-2′-pentenyloxyl]-ursan-3-one (momordicilin), a sterol 3β-hydroxy-stigmasta-5,14-dien-16-one (momordenol) and a monocyclic alcohol 1-hydroxy-1,2-dimethyl-2-[8′,10′-dihydroxy-4′,7′-dimethyl-11′-hydroxy methyl-trideca]-3-ethyl-cyclohex-5-en-4-one (momordol).
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