Ecdysone, structure

The most important steroid hormones in vertebrates are listed on p. 57. Calcitriol (vitamin D hormone) is also included in this group, although it has a modified steroid structure. The most important steroid hormone in invertebrates is ecdysone. 

This approach not only enabled the preparation of a simpler structure such as that of ecdysons (cf. 31), but also provides ways to introduce functional groups at C23 and C24 positions of the side chain. As an example, treatment of the mesylate 29 with non-nucleophilic te/7-butoxide gives the cyclopropane 32 which... 

Structure of /3-ecdysone and juvenile hormone. These hormones play major roles in the growth and maturation of insects by controlling the timing for molting of the insect exoskeleton. 

Antoniewski C., Laval M. and Lepesant J. A. (1993) Structural features critical to the activity of an ecdysone receptor binding site. Insect Biochem. Mol. Biol. 23, 105-14. 

Another developmental hormone is the juvenile hormone, which predominates early in larval life later ecdysone predominates. It is a methyl ester of the epoxide of a fatty acid derivative, and there is some evidence that its structure differs in different groups of insects. By a series of coincidences, it was discovered that certain paper toweling prevented the European bug, Pyrrhocoris apterus, from developing into sexually mature adults. Instead, an extra one or two larval molts ensued, and all eventually died without being able to complete metamorphosis. The juvenility factor was traced to particular conifers used in American paper pulp, mainly Abies balsamea, Tsuga canadensis, Taxus brevifolia, and Larix laricina. The active principle was isolated and characterized. It... 

The term ecdysteroid was originally defined as "all compounds structurally related to ecdysone" [4], However, Lafont and Horn [5] differentiated between true ecdysteroids and ecdysteroid-related compounds. True ecdysteroids possess a steroid nucleus with an A/B-cis-ring junction and a 14a-hydroxy-7-en-6-one chromophore, irrespective of their biological activity, while ecdysteroid-related compounds do not fulfil all these criteria. 

Scheme 3). A clone of cells from the midge Cbironomus tentans was found to be resistant to the effects of ecdysteroids because they metabolized 20-hydroxyecdysone rapidly. The initial oxidation product was 20,26-dihydroxyecdysone, but this was oxidized further to 20-hydroxy-26-oxo-ecdysone (21). This aldehyde (21) then formed a tautomeric equilibrium mixture of two cyclic hemiacetals (22) and (23), which were separable, isolated, and their structures determined (Scheme 3) with the use of acetonides (Section 4.03.3.6).32 These are the first examples of ecdysteroids with side-chain hemiacetals. Although 20,26-dihydroxyecdysterone still... 

Although ecdysone is the only steroid hormone in Drosophila of which the function is known, the haemolymph of the fly contains many other ecdysteroids, the function of which remains to be clarified. The haemolymph also contains the sesquiterpenoid, juvenile hormone (JH). In many insects, JH r ulates ecdysone release. JH has structural features in common with the retinoids and may signal through a nuclear RXR receptor. 

A detailed survey of the isolation and chemistry of the ecdysones has appeared. The isolation of deoxycrustecdysone (402a), deoxyecdysone (402b), and a-ecdysone (402c) has been reported. The structures of stachysterone A... 

Table IV lists structures of some uncommon conjugates to which NMR has been applied in characterizations. Both the xenobiotics and the conjugates are of diverse structural types. Ecdysone-type compounds, although not xenobiotics in the strict definition of the term, are included because they represent conjugation with a phosphate group.

The similarity of ecdysteroids and brassinosteroids may cause some difficulties in their definition. Ecdysteroids were initially defined as "all compounds structurally related to ecdysone" (3). This definition would include brassinosteroids. Recently an attempt has been made by Lafont and Horn to redefine ecdysteroids (6). According to their definition one may "distinguish between true ecdysteroids as compounds where the steroid bears a cis-fused A/B ring junction, a 7-ene-6-one chromophore and a 14a-OH (irrespective of activity in a moulting hormone assay) and ecdysteroid-related compounds which do not fulfil all the above criteria (either they lack the 14a-OH, or the 7-ene, or they present one additional 4- or 14-ene double bond, etc.)" (6). The latter group would include brassinosteroids. Unfortunately, comparable definitions of brassinosteroids are not available so far. 

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