YAMAGUCHI Lactonization Reagent

YAMADA Coupling reagent 430 YAMAGUCHI Lactonization reagent 431 YAMAZAKI Cyanoandme synthesis 432 Yamamoto 177... 

The regioselectivity of the addition of terminal alkynes to epoxides is improved, when the reagents prepared from the lithiated alkynes and either trifluoroborane or chlorodiethyl-aluminum arc employed (M. Yamaguchi, 1983 S. Danishefsky, 1976). (Ethoxyethynyl)lithium-trifluoroborane (1 1) is a convenient reagent for converting epoxides to y-lactones (M. Naka-tsuka, 1990 see p. 327f. cf. S. Danishefsky, 1976). 

Two short formal total syntheses were reported by Fujisawa, both employing diketene derivatives for C-1 to C-4 of the carbon framework. In the first sequence, Grignard reagent 38 was treated with 3-lactone 39 and a catalytic amount of Cul to afford allene 40 after acidic workup (Scheme 2.5). Base isomerization to a mixture of (f.Fj-and ( ,Z)-diene isomers 41 occurred in 85% overall yield. Lactonization using the Yamaguchi procedure (trichlorobenzoyl... 

Chapter Synthesis of 12- to 16-Membered-Ring Lactones is dedicated to the synthesis of 12- to 16-membered ring lactones. In this chapter, M. Kalesse and M. Cordes present an overview of the macrocyclization of seco-acids as well as new effective procedures to access 12- to 16-membered ring lactones such as ringclosing metatheses of alkynes and olefins. The authors also report the use of ketene sources and benzodioxinones to produce macrocyclic lactones. Nitrile oxide-olefin cycloaddition, intramolecular C-H oxidative macrolactonization, and Yamaguchi and Mukaiyama macrocyclization as well as macrolactonization via thioester or using phosphorus reagents are described. 

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