A synthesis of 11-homo-aldosterone

A synthesis of 11-homo-aldosterone acetate (1a) is described. 3β-Acetoxy-11-methylene-5α,25D-spirostan (3) was converted in 4 steps into 3β-acetoxy-11β-acetoxymethyl-5α-pregnan-20-one (9, Chart I), which was photocyclized to 20a, saponified regioselectively, and oxidized to 3-oxo-11β-acetoxymethyl-18,20-cyclopregnan-20α-ol-3-one (22, Chart II). Introduction of the 1,4-diene in 22 followed by a selective reduction of the 1-ene afforded 11β-acetoxymethyl-18,20-cyclopregn-4-en-20α-ol-3-one (26). Finally, the 18,20-cyclo ring of 26 was manipulated through 30, 31, 32, 33 to produce 1a. The bulky 11β-acetoxymethyl group distorted the steroid molecule to such an extent that the routine photochemical functionalization of the angular Me-18 via a nitrite or a hypoiodite became inoperative, and routine procedures for introduction of a 4-ene into 5α-3-one via a 1,4-dien-3-one were unsuccessful. Two new methods for the introduction of a 4-ene into steroidal 5α-3-ones were investigated using 5α-cholestanone and 5α-dihydrotestosterone as models. The first route, which was applicable to the synthesis of 1a, was the stepwise introduction of a 1-ene and a 4-ene utilizing Sharpless's acidic phenylselenyl chloride procedure, followed by a selective reduction of the 1-ene. The second route, which appeared equally promising, was protection of the C-2 site with N-methylanilinomethylene followed by introduction of the 4-ene and subsequent deprotection of the C-2.     

11-脱氧甘草次酸衍生物的合成

本文报道了具有潜在药理活性和应用前景的11-脱氧甘草次酸酯、11-脱氧甘草次酸盐的合成方法。     

A total synthesis of 11-O-methyldebenzoyltashironin

A concise total synthesis of 11-O-methyldebenzoyltashironin is reported in which oxidative dearomatization-IMDA-RCM triad constitutes the key ring forming steps, while an unorthodox DIBAL-H mediated stereo- and regioselective reductive epoxide openings and implementation of the vinyl bromide-carbonyl equivalency concept were pivotal to the success of this endeavor.     

A simplified [11C]phosgene synthesis

A new flow-through system for the production of [¹¹C]phosgene, a versatile labelling agent in radiochemistry for PET, is described. Cyclotron-produced [¹¹C]CH₄ is mixed with Cl₂ and converted into [¹¹C]CCl₄ by passing the mixture through an empty quartz tube at 510 °C. The outflow is directed through a Sb-filled guard that takes out Cl₂ and then, without intentional O₂ addition, through a second empty quartz tube at 750 °C, giving rise to [¹¹C]phosgene in 30–35% radiochemical yield.     

Asymmetric synthesis of rubiginones A(2) and C(2) and their 11-methoxy regioisomers

Convergent enantioselective syntheses of angucyclinone-type natural products rubiginones A(2) (2) and C(2) (1) and their 11-methoxy regioisomers 3 a and 3 b have been achieved by using two domino processes from a common enantiomerically pure 1-vinylcyclohexene 4. Key steps in the synthesis of this diene were the stereoselective conjugate addition of AlMe(3) on (SS)-[(p-tolylsulfinyl)methyl]-p-quinol (9) and the elimination of the beta-hydroxy sulfoxide fragment, after oxidation to sulfone, to recover a carbonyl group. The first domino sequence comprised Diels-Alder reaction with a sulfinyl naphthoquinone followed by sulfoxide elimination. An efficient opposite regioselection in the cycloaddition step was achieved in the convergent construction of the tetracyclic skeleton using a sulfoxide at C-2 or C-3 of the dienophiles 5 or 6, derived from 5-methoxy-1,4-naphthoquinone. The second domino process, triggered by oxygen and sunlight, allowed the transformation of the initial tetracyclic adducts into the final products after B ring aromatization, silyl deprotection and C-1 oxidation.     

Saturated nitrogen heterocycles. 11. Catalytic synthesis of 2-pyrrolidylalkanols

Furylakylamines have been catalytically converted into novel isomers of 2-pyrrrol-idylalkanols bearing a secondary alcohol group in the aliphatic chain, or a tert-butyl group attached to the heterocycle.For Communication 10, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1058–1061, August, 1988.     

A photochemical synthesis of 11H-benzo[a]carbazole

11H-Benzo[a]carbazole was prepared from 5-acetamido-1,2,3,4-tetrahydronaphthalene in four steps. A Goldberg arylation followed by hydrolysis afforded N-phenyl-1,2,3,4-tetrahydro-5-naphthylarnine ( 3 ). Photolysis of 3 produced 1,2,3,4-tetrahydro-11H-benzo[a]carbazole ( 4 ) which was converted to 11H-benzo[a]-carbazole by dehydrogenation with chloranil.     

A highly stereoselective synthesis of 11Z-retinal using tricarbonyliron complex

A stereoselective synthesis of 11Z-retinal 2, which is the chromophore of visual pigment (rhodopsin), was accomplished from the beta-ionylideneacetaldehyde-tricarbonyliron complex 3. The Peterson reaction of 3 using ethyl trimethylsilylacetate smoothly proceeded to afford predominantly the Z-ester 6. Transformation of the Z-ester 6 to the methyl ketone 19, followed by the Emmons-Horner reaction of 19 with C2-cyanophosphonate, produced ethyl 11Z, 13E-retinonitrile-tricarbonyliron complex 21 as the only product. Decomplexation of 21 with CuCl2 and subsequent DIBAL reduction gave 11Z-retinal 2 in excellent yield. Mechanistic consideration of Z-selectivity in the Peterson reaction of the aldehyde-tricarbonyliron complex is also discussed.     

The synthesis of 11β-alkyl-19-norsteroids: a novel class of potent steroid hormones—I : The synthesis of 11β-methyl and 11β-ethylestradiol

The syntheses of 11β-methyl and 11β-ethylestradiol, via Grignard adducts to 11-oxoestra-1,3,5(10)-trienes, attempted modification of the Torgov total synthesis of steroids, and 11β-methylticogenin, are described.     

A simple synthesis of heneicos-6Z-en-11-one — The sex pheromone ofOrgyia pseudotsugata

A method is proposed for synthesizing the insect sex pheromone heneicos-6Z-en-11-one and its homolog eicos-6Z-en-11-one.Moscow Technological Institute of the Meat and Dairy Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 102–104, January–February, 1980.     

The total synthesis of (+/-)-11-O-debenzoyltashironin

The total synthesis of the putative non-peptidyl neurotrophic factor 11-O-debenzoyltashironin has been accomplished. The key transformation involves a biomimetic oxidative dearomatization/transannular Diels-Alder sequence that closes the tetracyclic carbon skeleton present in the natural product.     

Total synthesis of nominal (11S)- and (11R)-cyclocinamide A

The cyclocinamides possess a unique β(2)αβ(2)α 14-membered tetrapeptide core. The initially reported biological data and intriguing structure, which was without full stereochemical identification, necessitated synthesis of both nominal (all-S) cyclocinamide A and the 11R isomer. The completed synthesis is highlighted by the use of a (cyclo)asparagine-containing dipeptide as a turn inducing fragment. Due to inconsistencies in analytical data between natural and synthetic samples, a re-evaluation of the natural product stereochemistry appears necessary.