Natural lignans

Etoposide is an effective anticancer drug used in the treatment of small-cell lung cancer, testicular cancer and lymphomas. It is a semi-synthetic modification of the natural lignan podophyllotoxin, and contains three acetal linkages. Can you identify them ... 

The bis(silyloxy)furans also react with substituted benzaldehydes in the presence of titanium tetrachloride to give diaryldioxabicyclo[3.3.0]octane-4,8-diones (39 equation 1) (80TL3427). Bis-lactones of this structure type have been isolated from the cultured mushroom Inonotus sp. K-1410. The bis(silyloxy)furans also hold promise for the construction of natural lignans that exhibit a skeleton made up of two fused tetrahydrofuran ring systems. 

Bis(trimethylsiloxy)furan (361) was reacted with a number of substituted benz-aldehydes with activation by titanium tetrachloride to give 2,6-diaryl-3,7-dioxobicyclo[3.3.0]octan-4,8-diones (362), the ring system occurring in natural lignan (80TL3427). 

Modified chiral biphosphinic dioxolane ligands and their use in the asymmetric synthesis of natural lignans 92H(33)435. 

The (S)-(+)-y-butyrolactone-Y-carboxylic acid is a useful Intermediate for the synthesis of pheromones,4 natural lignans,5 and other derivatives.6 In the same manner, but starting with D-glutamic acid, the (R)-(-)-lactone acid may be prepared. Lactonization occurs with full retention of configuration at the chiral center.8 9 Recently, authors have described an efficient method which allows the formation of derivatives of the (R)-(-)-lactone from the more available (S)-(+) counterpart.10... 

An accurate accounting of the total number of natural lignans of well-defined... 

Cp—Cp coupling occurs, probably via the first-formed palladium phenolate (315) to give the bisquinone methide (316), and the latter spontaneously undergoes intramolecular Diels-Alder reaction to the natural lignan carpanone (317) in 46% yield, with stereocontrol at five chiral centers. High yields, up to 94%, have been recorded using oxygen as oxidant with a metal(II)-salen complex as catalyst, e.g. cobalt(II) salen. A low yield of carpanone was also obtained in electrooxidation. 8... 

HC Schroder, H Merz, R Steffen, WEG Muller, PS Sarin, S Trumm, J Schulz, E Eich. Differential in vitro anti-HIV activity of natural lignans. Z Naturforsch 45c 1215-1221, 1990. 

PT Anastas, R Stevenson. Synthesis of natural lignan arylnaphthalene-lactones, daurinol and retrochinensin. J Nat Prod 54 1687-1691, 1991. 

Natural Lignans as Adhesives for Cellulose Computational Interaction Energy vs Experimental Results... 

---