Total synthesis of -confertin

Semmelhack, M.E, Yamashita, A., Tomesch, J.C., and Hirotsu, K., Total synthesis of confertin via metal-promoted cyclization-lactonization, J. Am. Chem. Soc., 100, 5565, 1978. 

TMs greatly improved the total synthesis of (+)-confertin [129b], in which Linstead cyclo-propanation originally [129a] had been used, too. 

Following model studies reported in 1976 (1, 92), it is satisfying to read that a total synthesis of ( )-confertin has been achieved by a nickel(0)-induced cycliza-tion of (103) to fused lactone (104). A total synthesis of optically active canadensolide (105) has been reported, starting from diacetone glucose. During the synthesis, considerable difficulties were encountered, especially in the final steps aimed at introduction of the a-methylene substituent. ... 

Further studies on the synthesis of psuedoguaianolides cf. Vol. 6, p. 90) have resulted in the total synthesis of the cytotoxic compounds ( )-damsin (447) (Scheme 43) and ( )-confertin (449) (Scheme 44). The realization that many sesqui-terpenoids containing a-methylene-y-lactone rings display important biological activity (cf. pp. 88 and 96) has prompted the development of several procedures... 

Cycloheptane derivatives (7, 192-193). Wender et a/. have applied their cycloheptane annelation procedure to total syntheses of the pseudoguaianolides damsinic acid (1) and confertin (2). The paper describes the synthesis of 1-lithio-l-methyl-2-vinylcyclopropane, which is the annelation reagent utilized in the pseudo-guaianolide syntheses. 

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