Synthesis of Lignans. I. Nordihydroguaiaretc Acid

Catalytic Asymmetric Intramolecular Hydroarylations of ω‐Aryloxy‐ and Arylamino‐Tethered α,β‐Unsaturated Aldehydes

“…Thus, the exact nature of this IR vibration in our spectra is contentious: it may be associated with NDGA, which is a dominant component of L. tridentata , or with the existence of a bond between Mg 2+ from L. tridentata and the oxalate ion from the calcium oxalate crystal surface, or with both. The possibility of NDGA is in good agreement with the previously reported IR absorption vibrational results in the literature for this compound or its derivatives extracted from L. tridentata , which exhibit strong absorptions in the wavenumber region around 3400 cm −1 10–12, 24. On the other hand, since magnesium is a central component of chlorophyll, Mg 2+ ‐related inhibition through formation of magnesium oxalate thin films at the surfaces of the crystals is likely to occur, too.…”

“…While L. tridentata retains greenery throughout the seasons, its bitter taste is toxic to livestock and most wildlife 6. Although its use for consumption is prohibited by the Food and Drug Administration of the United States and is discouraged by the modern medicine profession,7 its prominent beneficial effect as self‐medication for more than 50 diseases, such as renal, gallblader, and kidney stones, cancer, and tuberculosis, just to name a few, have led researchers to study its phytochemistry 8–12. Besides a number of glycosylated flavonoids, sapogenins, oils, halogenic alkaloids, and waxes,9 the most notable compound in this plant is nordihydroguaiaretic acid (NDGA),9–11 which has already been proven to have an antioxidant effect11 and to possess HIV Tat‐regulated transactivation 12…”

13C nuclear magnetic resonance spectral and conformational analysis of naturally occurring tetrahydrofuran lignans

“…The pounds (7). Since the 3-Me group of 8 is considered availability of galbacin (2b) and veraguensin (5b), to be free of steric interactions from the piperonyl isolated from V. surinamensis (3) and di-0-methyl-group of C-2 (7), it can be suggested that the shielding tetrahydrofuroguaiacin B (4) and galgravin (3b), of both methyls of 2b, at 13.7 ppm, is a consequence obtained by simple synthetic procedures (4,5), of a reciprocal y effect, owing to the puckering of C-3 prompted us to study these stereoisomers by 13C nrnr and C-4, confirming their pseudoequatorial orientaspectroscopy, in order to extract as much conforma-tion. The shift of C-l' and C-l" of 2b at 136.1 ppm, tional information as possible, and in continuation deshielded 2.1 ppm in comparison with C-I' of 8 and with our project on 13C nrnr spectral analysis of with a 6 value similar to the reported ones for C-1' lignans and related families of natural products (6).…”

Diastereomeric Discrimination in the Lifetimes of Norrish Type II Triplet 1,4‐Biradicals and Stereocontrolled Partitioning of Their Reactivity (Yang Cyclization versus Type II Fragmentation)

“…Configurational assignment of the diastereomers was based on comparisons of 1 H NMR spectroscopic chemical shifts of diagnostic methyl signals with those of analogous ketones reported in the literature. [9,23] Furthermore, the a-methyl carbon atoms of the syn and anti diastereomers of analogous ketones have been noted in the literature to exhibit distinct 13 C NMR spectroscopic chemical shifts: [24] the signal from the a-methyl carbon of the analogous syn diastereomer appears approximately 2-5 ppm further upfield than that of the anti. Thus, the 13 C NMR signal from the a-methyl carbon of the diastereomer of 2 assigned as syn based upon the 1 H NMR spectroscopic chemical shifts appears at 15.13 ppm, while that of the anti diastereomer resonates at 17.8 ppm.…”