Insects moulting

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. 

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]. 

Nonsystemic insect growth regulator with contact and stomach action. Acts at the time of insect moulting or at hatching of eggs... 

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... 

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... 

Effect of Ecdysteroids Brassinosteroids are structurally related to the insect moulting hormones, the ecdysteroids. Thus the question was raised whether... 

The naturally occurring cardenolides and the functions and chemistry of insect moulting hormones have been reviewed. The synthesis of steroid phosphates, sulphates, and glycosides has been summarised in a new book which draws attention to inadequacies in the current Rules of Carbohydrate Nomenclature when two types of glycosidic linkages are present, and in which is proposed a modification of these rules applicable to steroid glycosides. 

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... 

Insect juvenile harmones These act against insects by retarding their maturation. Steroidal insect moulting hormones such as (1-ccdysonc have been analyzed by HPLC. A study of the persistence of the synthetic juvenile hormone JH-25 [7-ethoxy - 1 (p-ethylphenoxy)-3, 7-dimethyl-2-octene] in flour samples has been carried out by HPLC. 

There are many examples of plants which produce insect hormones, for example, the insect moulting hormone, 20-hydroxyecdysone [179]. However, to date there had only been one report of the identification of an insect JH from a plant [155], It is obvious from the previous section, that we are in the preliminary stages of determining the role of JH III in C. iria. In an attempt to understand the role of this compound in the plant, we have characterized the distribution of JH III developmentally. At present, we can only speculate as to its possible biological activity(ies). 

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

From cholesterol 4.18) biosynthesis leads through truncation of the side-chain and other modifications to mammalian steroid hormones, e.g. oestrone 4.22) [11, 33]. Vitamin D3 4.24) is obtainable by photochemically mediated electrocyclic ring-opening of 7-dehydrocholesterol 4.23), followed by a thermal 1,7-sigmatropic hydrogen shift (Scheme 4.7) [34, 35]. The ecdysone insect moulting... 

Russell B, Fraser J G 1973 Insect moulting hormones Dacrysterone, a new phytoecdysone from Dacrydium intermedium. Aust J Chem 26 1805-1807... 

Galbraith MN, Horn DHS 1966 Insect-moulting hormone from a plant. J Am Chem Soc Chem Commun 905-906... 

An important hormone in insects is the so-called juvenile hormone, produced in the corpora allata, a part of the brain. It acquired that name because it is required at each moult between immature stages (see Figure 1.4). When JH is absent, the insect moults to the adult form. But the hormone is also produced in adult insects and has other functions there. Pheromone release in Lepidoptera and Coleoptera is often under the control of JH. 

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