Lactone Entities

Scheme 11 Formation and hydrolysis of glucono-1,5-lactone and 2, 6- and 3,6-lactone entities...

PhjSnH-AIBN in toluene (10 examples, 72-99%). Accordingly, a two-step conversion of esters and lactones to ethers via thionoesters/lactones can be achieved on this basis. 2-Thiono-l,3-dioxolanes are similarly desulfurized to give the dioxolanes, therefore diols can be protected in the form of heterocycles which are acid-stable but eventually switched to acid-sensitive entities. 

Another of the earhest uses of an intermolecular [4+3] cycloaddition reaction was the stereoselective preparation of the synthetic intermediate, the Prelog-Djerassi lactone 29 [17]. This lactone is an important intermediate for the preparation of macrolide antibiotics [18]. The authors were also one of the first to use the [4+3] cycloaddition to stereoselectively install multiple stereocenters simultaneously and to transform the core cycloadduct into another molecular entity. 

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