Steroids hydrazones

Lehn synthesised guanidinium-based cationic steroids incorporating an acylhy-drazone linker using the approach shown in Fig. 9 [141]. The synthesis was developed from a polyamine scaffold by guanidination of the primary amino groups and alkylation of the secondary amine with methyl chloroacetate to introduce the ester moiety required to form a hydrazide group by reaction with hydrazine monohydrate. Cationic steroid hydrazones were then prepared via an acetic acid catalysed reaction with cholestanones, which demonstrated high transfection efficiency and low toxicity in a variety of cell lines [141]. 

Hydrazones.—Oxidation of hydrazones with lead tetra-acetate gives nitrogen and a mixture of acetates and olefins, apparently through the intermediacy of diazo- and diazonium compounds (Scheme 18). The steroid hydrazone at C-7 affords mainly the 7a-acetoxy-derivative, but at C-3 a mixture of 3a- and 3j8-acetoxy-compounds results, together with an olefinic fraction. ... 

Steroid ketones Apply the sample solution followed by Girard s reagent (0 1% tnmethylacetyl hydrazide in 10% acetic acid) and allow to react for 15 h in an atmosphere of acetic acid Then dry at 80 °C for 10 mm and after cooling chromatograph the hydrazones that have been formed [81]... 

Some advantages of this reaction are high yield if the tosylate is in a sterically accessible position excellent isotopic purity of the product (usually higher than-95%) and perhaps most important, access to stereospecifically labeled methylene derivatives. For example, deuteride displacement of 3j -tosylates (183) yields the corresponding Sa-d derivative (185) in 96-98% isotopic purity. Application of this method to the labeled sulfonate (184), obtained. by lithium aluminum deuteride reduction of a 3-ketone precursor (see section HI-A) followed by tosylation, provides an excellent synthesis of 3,3-d2 labeled steroids (186) without isotopic scrambling at the adjacent positions. The only other method which provides products of comparable isotopic purity at this position is the reduction of the tosyl-hydrazone derivative of 3-keto steroids (section IV-B). 

Iodine fluoride is a more versatile reagent than molecular fluorine in geminal fluorination of other hydrazones and related compounds under milder reaction conditions [55] Substrates fluorinated include hydrazones of simple cyclic or steroidal ketones (e g, 4 tert butylcyclohexanone, 70%, 3 cholestanone, 70%), W methyl and A/N dimethylhydrazones [R2C=NNH(CH3) 70%, R2C=NNC(CH3)2, 50%], semicarbazones (R2C=NNHCONH2, 25-50%), and 2,4-dinitrophenylhy-drazones [R2C==NNH-C6H3-2,4(N02)2, 25-50%]... 

In contrast to the Johnson s D —> A-ring construction approach, Brown devised an A —> D-ring construction approach [22]. Starting from Wieland-Miescher ketone (30), a common source of the A, B-rings in the de novo synthesis of steroids, the C-ring was introduced via hydrazone allylation, ozonolysis, aldol condensation, and olefin isomerization (31 > 32). The D-ring was assembled by a reductive alkylation... 

Others have reported the use of fluorescent dansyl derivatives for the identification of 17a-oestradiol from serum samples (O Figure 2-2) (Nozaki et al., 1988). The derivatization of the keto functional group of particular steroids (ketosteroids) can also be achieved by hydrazone formation (O Figure 2-3) the most... 

Oximes, Hydrazones, and Semicarbazones.—Hydrazones and semicarbazones of 3-oxo-A - and -A -steroids may be smoothly converted into the parent ketones by treatment with benzene seleninic anhydride. ... 

Weiss and co-workersprepared a series of oxazohnylidene steroids 343 as luminescence dyes for application as potential intracellular diagnostic agents (Scheme 6.72). The key intermediate 2-aryl-5,5-dimethyl-4(57/)-thiooxazolones 341 were readily available from the corresponding 4(57/)-oxazolones 339. Reaction of 341 with 342, generated in situ from the hydrazone 340, gave 343 as expected. It was not possible to prepare 343 from 3-thio-androsta-l,4-dien-17-one since the requisite corresponding heterocyclic diazo compounds could not be prepared. 

Griffiths et al. [23] studied the ESI MS of sterols, and while they are not hormonal steroids, similar derivatization methods can be used. He converts 3/5-hydroxy-A5 sterols to - -4-ene sterols using cholesterol oxidase and follows this by preparation of Girard P hydrazones. This increases the sensitivity by 1000 in ESI. This technique would also be applicable to pregnenolone, dehydroepiandrosterone (DHEA) and similar A5 steroids, which can also be oxidized by cholesterol oxidase. 

The reduction of tosylhydrazones by complex metal hydrides has been used very effectively to prepare saturated steroid hydrocarbons in high yields.317 In certain cases this reduction (with lithium aluminum hydride) takes a different course, and olefins are formed.318 The effect is dependent on both the reagent concentration and the steric environment of the hydrazone.319 Dilute reagent and hindered hydrazone favor olefins borohydride gives the saturated hydrocarbon. The hydrogen picked up in olefin formation comes from solvent, and in full reduction one comes from hydride and the other from solvent. This was shown by deuteriation experiments with the hydrazone (150) 319... 

Dinitrophenylhydrazine has been used by several workers [34-36] for the analysis of keto acids in biological fluids. The hydrazones are formed as described for steroids or by the method of Katsuki et al. [34]. 

DNS-hydrazine (5-dimethylaminonaphthalene-l-sulphonylhydrazine) reacts with the keto groups of keto steroids to form fluorescent hydrazones. The derivatives are separated by TLC and are quantitated by fluorimetry at 340 nm (excitation) and 525 nm (emission). 

Method. 0.2 ml of an ethanolic solution of hydrochloric acid (0.65 ml of concentrated hydrochloric acid per litre of absolute ethanol) is added to the dry keto steroid in a small test-tube [103,104]. 0.2 ml of a solution of DNS-hydrazine (2 mg/ml in absolute ethanol) is then added. The contents of the test-tube are heated in a bath in boiling water for 10 min for hydrazone formation. The tube is cooled and 0.2 ml of sodium pyruvate (5 mg/ ml in absolute ethanol) is added to destroy the excess of DNS-hydrazine. The tube is permitted to stand at room temperature for 15 min. 6 ml of diethyl ether and 3 ml of Q.5-N aqueous sodium hydroxide are then added and the tube is shaken. The diethyl ether layer is removed and evaporated to dryness. The residue is dissolved in a small volume of chloroform (0.2-0.5 ml) for TLC analysis. The keto steroid derivatives are separated on layers of Alumina G (Woelm) (thickness, 250 fim) which have been activated at 120 °C for 30 min. The solvent consists of dioxane-chloroform (1 9). The separated derivatives are observed under UV light at 366 nm. The limits of detection are in the 1-2 nmole range for each steroid. 

The oxidation of a 12-hydrazone (248) with lead tetra-acetate provided a novel route to rearranged steroids with the C-nor-D-homo structure (249), although another isomer was formed simultaneously. Dehydration of a C-12 cyanohydrin with thionyl chloride gave the 13a-cyano-c-nor-D-homo-compounds (250) and (251).209... 

Annelation of steroidal dienamines with substituted phenacyl bromides (7 examples) or with benzenediazonium salts (11 examples) has been shown to lead to the corresponding furano- and indolo-steroids.89 Thus the A3,5-dienamine derived from A4-androstene-3,17-dione reacted with p-bromophenacyl bromide to yield the A5-androstano[3,4-h]furan (199) in 26% yield, and reaction of the same A3,5-dienamine with benzenediazonium fluoroborate at -45 °C led to formation of the hydrazone (200) which underwent Fischer-indole cyclization on treatment with phosphorus oxychloride to produce the A4-androstano[6,7-6]indole (201). The A3,5-dienamine derived from 17/3-acetoxyandrost-4-en-3-one has been converted into the benz[4,5,6]-steroid (202 R1 = Me, R2 = H) by reaction with methyl vinyl ketone and into the analogous benzsteroid (202 R1 = H, R2 = Me) on treatment with crotonal-dehyde.90 A route to the condensed pyrroline ring system (203) has been devised... 

The fused pyrrole ring system (204) has been obtained by the reaction of 17/3-hydroxy-17-methylandrosta-l,4-dien-3-one with tosylmethyl isocyanide in the presence of sodium hydride in DMSO,92 and 17/3-hydroxy-17-methyl-7-oxa-5o -androstano-[3,2-c]- (205) or -[2,3-d]-isoxazoles (206 X = O) have been prepared by treating 7-oxa-2-(hydroxymethylene)-17/3 -hydroxy-17-methyl-5 a -androstan-3-one with hydroxylamine hydrochloride.93 In the presence of pyridine, the isox-azole (206 X = O) is formed, but when the reaction is catalysed by sodium acetate in acetic acid the isomeric steroid (205) results. Cycloaddition of hydrazine hydrate to the same 2-hydroxymethylene-7-oxa-steroid results in the [3,2-c]pyrazole (206 X = NH). A similar addition is encountered in the reactions between 3/3-hydroxy-16-(hydroxymethylene)-5a-androstan-17-one and the substituted hydrazines RNHNH2 (R = H, o-COC6H4NH2, or p-COQHUNH ,) when the corresponding [17,16-c]pyrazoles (207) are formed after cyclization of the intermediate hydrazones.94... 

The unsubstituted hydrazones derived from aromatic ketones (Table 1 entries 1, 5, 7,10, 11) a nd a Idehydes (entries 14 and 17), cyclic ketones (entries 19,24,25). including 3-oxo steroids (entries 28 and 29), as well as aliphatic ketones (entries 31, 34, 39) and aldehydes (entry 41) react under mild conditions yielding the expected gew-difluoro compounds. If the monohy-drazone of a diketone can be prepared, a,a-difluoro ketones are also available (entry 42). 

The main use of hydrazine in steroid chemistry has been in the reduction of keto-groups to give unsubstituted methylene groups by the Wolff-Kishner process, particularly as modified by Huang-Minion fij. Hydrazones of simple ketones react rapidly at 200° in hydroxylic solvents such as "diethylene glycol containing strong alkali. 

A novel reaction of hydrazones, including steroid derivatives, is their oxidation by iodine and triethylamine to give vinyl iodides (or diiodo compounds from aldehyde hydrazones) [x6]. Oxidation by iodine in a neutral non-polar solvent gives azines through the free-radical process ... 

The basic triethylamine promotes an ionic reaction leading to the diazo compound (32), which then reacts with iodine in tetrahydrofuran probably through the iodonium compound (23) to give the iodo-product (24. Steroidal 17- and 20-hydrazones give the vinyl iodides (25) and (26) respectively. 

Variations in reactivity and product character have been observed when the original ketone is conjugated with another unsaturated group. Steroidal A -3 hydrazones (5) undergo double-bond migration to give (7) and A -5j3-olefins... 

Most steroid ketones react readily with tolnene- Siilphonyl hydrazide -CH3 C6H4 S03 NH NH2) to form crystalline derivatives ( tosylhydrazones ) which are valuable intermediates for the preparation of olefins and fully-saturated unsubstituted products. Three modes of reaction of tosyl-hydrazones have become important. 

As previously discussed, Wolff-Kishner reductions are hampered by steric hindrance surrounding the carbonyl primarily due to difficulty in the requisite hydrazone formation. Forcing conditions such as the Barton and Nagata modifications have alleviated many of the problems with hindered ketones (i.e. 11-keto steroids, equation 4), but unyielding problems still remain (i.e. structures 10 and 11) requiring alternative strategies for oxygen removal. 

As mentioned, LiAlH4 in refluxing THF was the initial system introduced to reduce preformed tosyl-hydrazones to hydrocarbons and a number of successful conversions have been reported, representative examples of which are presented in Table 5. Alkene side products often accompany the hydrocarbon products,a result attributed to proton abstraction from the a-carbon of intermediate (59), leading to a vinyldiimide anion (64), followed by N2 expulsion and protonation during work-up (Scheme 3). With certain ketones, including 17-keto steroids, alkenes are the major s or sole product (entries 7-9, Table 5). This side reaction mimics the elimination obtained upon treatment of to-sylhydrazones with other strong bases (i.e. alkyllithiums, the Shapiro reaction 29). Note that use of LiAlD4 introduces one deuterium (with H2O work-up) or two deuteriums (with D2O work-up entries 5 and 6, Table 5, respectively). 

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