Naturally occurring cyclic hydroxamic acids

The following discussion of hydroxamic acids includes saturated systems, e.g., 2, compounds such as 3, derived from aromatic systems, 7V-hydroxyimides such as 7V-hydroxyglutarimide (78), and certain of their derivatives including thiohydroxamic acids. Naturally occurring cyclic hydroxamic acids are discussed to show the range of structural types that has been found, hut macrocyclic polyhydroxamic acids are mentioned very briefly, because several comprehensive reviews of these compounds are already available. The main purpose of this review is to summarize the methods available for the synthesis of cyclic hydroxamic acids, to outline their characteristic reactions, and to present some useful physical data. Their synthesis and some biological properties have previously been reviewed by Coutts. ... 

For the present purpose this is not a useful scheme and the naturally occurring compounds are arranged instead in order of increasing molecular complexity. Compounds that do not contain a cyclic hydroxamic acid structure are excluded. 

Hydroxy- and l,4-dihydroxypiperazine-2,5-diones belong to the class of cyclic hydroxamic acids. This moiety is known to occur in several natural products, such as mycelianamide. The chemistry of these fungal metabolites has been discussed by Sammes (75FOR51). A more recent review has also covered some synthetic aspects of 1-hydroxypiperazine-2,5-diones (88FOR203). 

Because this paper deals in particular with benzoxazolinone chemistry, we will only present a survey of naturally occurring acetal glucosides with cyclic hydroxamic acid moieties (Fig. 4.2) as precursors of aglucones (Fig. 4.3) which may decompose to (substituted) benzoxazolin-2(3H)-ones (Fig. 4.4). 

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