H and 13C NMR data

Structure of Oxy-F Compound F is extremely unstable and is difficult to obtain at a level of purity suitable for NMR studies. However, an oxidation product, Oxy-F, formed when F is left standing at — 20° C, is considerably more stable than F and can be purified to a sufficiently high level of purity. Oxy-F is nonfluorescent and shows absorption maxima at 237 nm and 275 nm (shoulder). The high-resolution FAB mass spectrum indicated the molecular formula of Oxy-F to be C33H3809N4Na2 [m/z 703.2363 (M + Na)+ and 681.2483 (M + H)"1"]. The H and 13C NMR data allowed the assignment of structure 7 to oxy-F (Fig. 3.2.6 Nakamura et al., 1988). 

The H and 13C NMR data for the three metal derivatives were similar. An X-ray crystallographic structure for the gallium derivative (Fig. 6) indicated a shortened Ga—C (carbene) distance of 1.935(6) A, whereas the Ga—C(Me) distances had normal single bond values, 1.994(8) and 1.988(8) A. Thus, the structure may be visualized as being composed of the two canonical forms... 

Pertinent H and 13C NMR data are included, where available, in Schemes 4.43 and 4.44. As expected, trans F—H coupling is character-... 

More recently, the prostanoid metabolites of P. homomalla have been reinvestigated relative to their potential natural function [69], A minor new metabolite was isolated and characterized in this work by high field NMR studies. Its structure, the 9-O-acetate of methyl PGF2ar (55), seems secure given the opportunity to compare H and 13C NMR data sets with an earlier isolate of the 11-O-acetate of PGF2c( (56) [70],... 

An improved version of the Knoevenagel reaction between acetophenones and aldehydes allows direct access to trarcr-2,3-disubstituted chroman-4-ones, examples of which show high anti-estrogenic activity <00T1811>. Reduction of flavanones by NaBUi leads to the 2,4-cis-flavan-4-ols from which 4-methoxyflavans can readily be obtained detailed H and 13C NMR data are provided <00T6047>. 

As mentioned above, persistent carbocation 9 underwent rearrangement into cation 10 which rearranged further into cation 11. To reveal general relations/factors governing cationic rearrangements in benzopentalene derivatives, the behavior of 5,5,10,10-tetramethyl-5,10-dihydroindeno[2,l-fl]indene (12) in superacids was studied (52). It had been expected that hydrocarbon 12 would transform into the long-lived 5,5,10,10-tetramethyl-4b,5,9b,10-tetrahydroindeno[2,l-a]inden-4b-yl cation (13). However, H and 13C NMR data showed that hydrocarbon 12 transformed firstly into isomeric ion 14 which transformed further into cation 15 (Scheme 11). 

Licania heteromorpha var. heteromorpha Bentham is a tree up to 30 m high native to the Amazonian forest. Phytochemical study of its aerial parts yielded both triterpenes and flavonoids triterpenes were obtained from the chloroform extract by silica gel column followed by RP-HPLC and were characterised as betulinic acid (11), alphitolic acid (48), 3(3-0-trans-p-coumaroyl alphitolic acid (49), 3(3-0-cw-p-coumaroyl alphitolic acid (50), 3 -0-trans-p-coumaroyl maslinic acid (51), 3fi-O-cis-p-coumaroyl maslinic acid (52), 3(3-0-tnms,-/ -coumaroyl-2a-hydroxy-urs-12-en-28-oic acid (53), 3 3-0-m-p-coumaroyl-2a-hydroxy-urs-12-en-28-oic acid (54) [see Fig. (2) and (6)] [15], Compounds 11 and 48-54 were identified comparing their H and 13C NMR data with those previously described. Triterpenoids 48-54 were found for the first time in Licania, while betulinic acid had been isolated previously from L. carii [9]. On the other hand, flavonoids were isolated from the chloroform-methanol and methanol residues by Sephadex LH-20 and HPLC they were identified as myricetin 3-0- 3-D-galactopyranoside (17), myricetin 3-0-a-L-rhamnopyranoside (32), myricetin 4 -methylether-3-0- 3-D-glucopyranoside (55), myricetin 4 -methylether-3-0-a-L-rhamnopyranoside (45), myricetin 3,4 -di-0-a-L-rhamnopyranoside (56), myricetin 7-methylether 3,4 -di-0-a-L-rhamnopyranoside (57), and myricetin 4 -methylether-3-0- 3-D-galactopyranoside (58) [see Fig. (2), (4), and (6)]. The last three myricetin derivatives were new natural compounds [16]. Known compounds were identified by comparison of their H and l3C NMR spectra with those reported in the literature [15]. 

H- and 13C-NMR Data for ct-Adducts as Formed from Diazines and the Amide 1on°... 

The primary cycloadduct from combination of a dipolarophile with a silyl nitronate is an isoxazolidine. The H and 13C NMR spectra are highly informative for the structural determination of these products, Tables 2.7 and 2.8 (21,25,34,35). Both the H and 13C NMR data show that HC(5) are shifted downfield relative to HC(3). An expected downfield shift is also observed with electron-withdrawing or conjugating groups. In the absence of functionalization at C(3), there is a significant upfield shift of the corresponding 13C resonance. The IR data is less reliable. The O—N—O stretch is reported to be 1055 cm-1 (Fig. 2.8), however, this stretching... 

Schiff Bases as Acyclic Polydenlate Ligands Table 3 H and 13C NMR Data for some Monoimines"... 

H and 13C NMR data for anopterine [570] have been reported, (336) and the 13C NMR spectrum of miyaconine [571] suggests cr-orientation of the 2-hydroxyl group. (337)... 

Several H and 13C NMR data of azetidines and azetidin-3-ones have been reported. A significant variation is observed in geminal coupling constants of the methylene group attached to nitrogen of different classes of azetidines. The substituents at the nitrogen atom and the conformations of the compounds appear to affect the J values. 

The reactions of 3,3-dichloroazetidines to afford aziridines were performed in an NMR tube to prove the intermediacy of 2-azetines 574 <2002JOC2075>. The H and 13C NMR data of 2-azetines are reported. The H and 13C NMR data of 1-azetines are described in CHEC-II(1996) <1996CHEC-II(1B)507>. 

Since calotropagenine, the aglycone of uscharidine, is accessible only with difficulty, model experiments have been carried out with the more readily available cholestan-2oc,3P-diol 21. On Ag2C03-mediated reaction with actino-spectosyl chloride 18 two isomers formed smoothly in an approximate 3 1 ratio, of which the major one - as evidenced by H- and 13C-NMR data, corroborated by NOE experiments - proved to be the "unnatural" anellation product 23. The minor product 22, however, could be readily debenzoylated by treatment with butylammonium acetate in aqueous acetonitrile to afford the uscharidine analog 24 albeit in modest yield (46), yet crystalline form so that its linkage geometry could be secured by an X-ray structure analysis (47). 

Detailed H and 13C NMR data on a variety of dihydro-2/7-selenopyrans have also been reported <1995JA10922>. 

All reactions were carried out under an argon atmosphere. The solvents used were of commercial p.a. quality. H and 13C NMR data were obtained on a Bruker ARX 400 spectrometer. Phase transitions were studied by differential scanning calorimetry (DSC) with a Bruker Reflex II thermosystem at a scanning rate of 10 °C min-1 for both heating and cooling cycles. UV-Vis and fluorescence spectra were recorded on a Jasco V-550 spectrophotometer and a Varian-Cary Eclipse spectrometer, respectively. Low-resolution mass spectra were obtained on a Varian... 

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