Ecdysone, moulting hormone

The A -6-ketone functionality in polyhydroxy cholestanes is common to all the insect moulting hormones of the ecdysone type. Therefore, there has recently been considerable interest in the introduction of A -double bonds into 6-ketones. The different approaches that follow illustrate the utility of isomerization, rearrangement, and blocking groups. 

Bryant Is that moulting controlled by an ecdysone-like hormone ... 

Most of the more recently described allenic steroids bear an allene group at the 17-position, which was usually formed by an SN2 substitution [106] or reduction [86d] process of a suitable propargylic electrophile. Thus, reduction of the pro-pargylic ether 109 with lithium aluminum hydride followed by deprotection of the silyl ether resulted in the formation of the allenic steroid 110, which irreversibly inhibits the biosynthesis of the insect moulting hormone ecdysone (Scheme 18.35) [107]. 

Juvenile hormone plays a critical role in maintaining the juvenile or larval stage of insects, and if its secretion is not controlled, normal development to the adult stage is prevented. Use of hormones or substances with hormonelike activity to control insect populations is an area of intense research interest and activity.2 The secretion of juvenile hormone is controlled by other hormones originating in the brain (brain hormone) and the phthoracic gland (moulting hormone, ecdysone see Table 30-2). 

The biosynthesis of insect moulting hormones has been reviewed.340 Labelled MVA and cholesterol were incorporated (0.5 and 1%, respectively) into inoko-sterone and /3-ecdysone (110) by seedlings and homogenates of Achyranthes... 

Ecdysone is a steroid that is formed and secreted by the prothoracic glands of immature insects but also by the ovaries of adult female insects. It was first isolated from the silk worm, Bombix mori. Bedstone is the prohormone of the moulting hormone eedysterone, but the prohormone has also effects on its own at other stages of insect development. 

Sterols. A considerable amount of work was devoted to the study of backbone rearrangements. - While partial syntheses of an insect moulting hormone, ecdysone, were announced by several groups, evidence is accumulating on the widespread occurrence in natxire of its hydroxylated derivatives. This year saw the isolation of 20-hydroxy-ecdysone - - from silkworm (ecdysterone), crayfish - (crustecdysone), oak-silk moth, tobacco hornworm, and from plants such as Podocarpus nakaii, Podocarpus elatus, and Achyranthis. The ready isolation of insect-moulting hormones from plants in contrast to -the extremely poor... 

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. 

The biosynthesis and metabolism of the insect moulting hormone, ecdysone have been the subject of recent reviews [184-186]. Ecdysone (107) was first isolated in a crystalline form from the silkworm, Bombyx mori, by Butenandt and Karlson in 1954, and the structure was determined in 1965. Soon after, the second moulting hormone was isolated and the structure was elucidated as 20-hydroxyecdysone (108). Ibe same hormone was also isolated from the sea-water crayfish, Jasus lalandei by Horn in 1966. Many ecdysone analogues were isolated from arthropods and certain... 

Butenandt and Karlson (1954) isolated the moulting hormone and called it a-ecdysone (80). The elucidation of its structure is associated with the name of Karlson et al. (Karlson et al., 1963 Huber and Hoppe, 1965 Hoppe and Huber, 1965). 

Rees, Studies on insect moulting hormones Biosynthesis of ecdysone, ecdysterone, and 5 3-hydroxyecdysterone in Polypodium vulgare. Phytochemistry, 9, 1247-1252 (1970). 

Moulting Hormones - The structure of ponasterone B and C (24), the synthesis of A and its identity with crustecdysone (25) have been reported > > f Similar hormones are podecdysone A and the amarasterones . The synthesis of active pregnan-6-ones has appeared and some effects of ecdysone and analogs on the development and reproduction of insects were published . Inhibition of larval growth and development was seen with several ecdysone... 

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