Studies on the Degradation of Lignin and Model Compounds. I. The Configuration of Dehydrodiisoeugenol.

The Relative Configuration of Grossamide and Hordatines

“…The reaction mixture was added to NaCI solution and shaken with ethyl acetate (200 ml x 3). The combined extracts were dried on NaZS04 and concentrated in vacuo to a syrup (1.58 g), which was chromatographed over silica gel-celite (130 g: 20 g), using nhexan~thyl acetate (3: I), to afford 378mg of dimethyl dehydrodiferulate (5) (7). Methyl p-coumarate (12, 1.7 g) was treated as the same way as described above, and dimethyl dehydrodi-pcoumarate (7) (5) to dehydrodiconiferyl alcohol (60).…”

“…This similarity of chemical shifts means that above three compounds (3b, 4b and 7) have the same configuration. By reduction with lithium aluminum hydride, the signal at c5 6.03 ppm assigned to 7-H in ester (7) shifted to the upper field, c5 5.45 ppm, in alcohol (8). On the basis of this large upfield shift (LI 0.58 ppm) of 7-H, it seems most reasonable to conclude that the carbonyl and the phenyl groups in the hordatines (3a, 4a) are also trans.…”

“…In garcinia and hibiscus acids,3) for example, the deshielding effects are in the range of 0.37 ~ 0.60 ppm, which is large enough to discuss the stereochemistry. Fortunately, the lignan amides, grossamide (1) and hordatines (3a, 4a), have carbonyl and methine groups as vicinal substituents in dihydrobenzofuran moiety, and we are able to compare their spectra with those of the model compounds: dimethyl dehydrodiferulate (5), dehydrodiconiferyl alcohol (6a), dimethyl dehydrodi-p-coumarate (7) and dehydrodi-p-coumaryl alcohol (8).…”

“…The ester (7) was insoluble in D 2 0, a mixture of D 2 0 and acetone-d 6 being used as the solvent. The chemical shifts of 7-H of the two diacetyl hordatines (3b, 4b) and the model compound (7) are c56.19, 6.19 and 6.01 ppm respectively (Table I). This similarity of chemical shifts means that above three compounds (3b, 4b and 7) have the same configuration.…”

The Stereochemistry of β—5 Lignin Model Compounds

“…Conflicting stereochemical predictions have been derived from NMR (Ludwig et a!. 1964) and chemical (Aulin-Erdtman et al 1963) evidence. We sought to resolve this conflict unambiguously by an X-ray diffraction crystal structure determination of dihydrodehydrodiisoeugenol.…”