Ethylidene Derivatives Research Articles

Different reactivities of acetylated exo- and endo-cyanoethylidene derivatives in glycosylation reactions

The condensation of acetylated 1-( endo-cyano)ethylidene derivatives having the d- gluco, d- xylo, and d- galacto configurations ( 2– 6) with a primary ( 8) and a secondary ( 9) trityl derivative was more rapid than for the corresponding exo-isomers. This difference in reactivity is explained on the basis of differences in conformation.

Syntheses of Bile Pigments. Part 16. Synthesis of a vinyl‐substituted 2,3‐Dihydrobilinedione: Possible role of this new class of bile pigments in phycobilin biosynthesis

AbstractThe total synthesis of racemic cis‐2,3,181, 182, ‐tetrahydroprotobiliverdin IXα dimethyl ester (19b), which is identical with the dimethyl ester of rac‐4, is described (Scheme 2). Under virtually neutral conditions, in solution, this bile pigment isomerized within a few min to racemic Z‐phycocyanobilin dimethyl ester (rac‐5b). Likewise, acid‐catalyzed allyl rearrangement of 3‐vinyl‐substituted cis‐ and trans‐2,3‐dihydrodipyrrin‐1(10H)‐ones 11c and 13c, respectively, yielded the corresponding ethylidene derivatives. In this case, however, the E‐isomer was formed stereo selectively from both substrates. The above results prove that, if protobiliverdin IXα (2) is transformed enzymatically to its 2,3,181, 182‐tetrahydro derivative, the latter would isomerize spontaneously to phycocyanobi‐lin. The biosynthesis of bacteriochlorophyll a and b from a common precursor bearing a vinyl group at C(8)may be straightforwardly explained in the same way.

A model for triterpene side-chain synthesis. 2

A bicyclic model for 17-keto derivatives of triterpenes, trans -1,6-dimethyl-2-methoxybicyclo[4.3.0] nonan-7-one (1), was used to explore side-chain construction concurrent with oxidation at C-8 (triterpene C-16). Oxidation of methylene derivative 2 with selenium dioxide gave β alcohol 14, and borohydride reduction of the corresponding ketone ( 15) led to the α epimer 16. Each allylic alcohol ( 14 and 16) reacted stereospecifically with phenylsulfenyl chloride to give, respectively, diastereoisomeric sulfoxides 20 and 19. The latter yielded a conjugate base that was methylated selectively to give sulfoxide 21. Desulfuration of 21 with trimethylphosphite generated the ethylidene α alcohol 22, and following PDC oxidation, E enone 25.This enone was a minor product from an alternative synthesis beginning with ethylidene derivative 3. Treatment of 3 with selenium dioxide followed by PDC gave the isomeric Z enone 24 as the major product. Reaction of 24 with lithium bis-4-methyl-3-pentenylcuprate proceeded by a facial-selective conjugate addition to the euphane CD model 26. The E isomer 25, under similar conditions, gave only an unresolved mixture. These results are compared with similar steroid reactions reported by Trost and Schmuff 11.

ChemInform Abstract: Formation of 1,2‐O‐(1‐Methoxycarbonyl)ethylidene Sugar Derivatives from 1,2‐O‐(1‐Cyano)ethylidene Derivatives and Reverse Transformation.

ChemInform Abstract: Formation of 1,2‐O‐(1‐Methoxycarbonyl)ethylidene Sugar Derivatives from 1,2‐O‐(1‐Cyano)ethylidene Derivatives and Reverse Transformation.

ChemInform Abstract: Preparation of Tritylated 1,2‐O‐(1‐Methoxycarbonyl)ethylidene Derivatives of Carbohydrates and Their Conversion into Tritylated 1,2‐O‐(1‐Cyano)ethylidene Derivatives.

ChemInform Abstract: Preparation of Tritylated 1,2‐O‐(1‐Methoxycarbonyl)ethylidene Derivatives of Carbohydrates and Their Conversion into Tritylated 1,2‐O‐(1‐Cyano)ethylidene Derivatives.

Preparation of tritylated 1,2-0-(1-methoxycarbonyl)ethylidene derivatives of carbohydrates and their conversion into tritylated 1,2-0-(1-cyano)ethylidene derivatives

Tritylation of 1,2-0-1-(methoxycarbonyl)ethylidene derivative of carbohydrates followed by ammonolysis of the methoxycarbonyl group and dehydration was proposed as an alternative method for the preparation of tritylated 1,2-0-1-(cyano)ethylidene derivatives for use as monomers for polycondensation.

Formation of 1,2-0-(1-methoxycarbonyl)ethylidene derivatives of sugars from 1,2-0-(1-cyano)ethylidene derivatives and reverse transformation

1,2-0-(1-Methoxycarbonyl)ethylidene derivatives of sugars formed during the methanolysis of 1,2-0-(1-cyano)ethylidene derivatives can be converted into the initial cyanoethylidene derivatives. Consequently, the 1,2-0-(1-methoxycarbonyl)ethylidene function was proposed as a unique protecting group for 1, 2-0-(1-cyano)ethylidene function.

Structural Assignments of Ethylidene Acetals by NMR Spectroscopy

Abstract The 1H and 13C NMR spectra of ethylidene derivatives of simple diols and of carbohydrates were measured to determine whether NMR parameters could be found which could be related to structure. Four NMR parameters were considered; the chemical shifts of the acetal proton and carbon, the 2JC,H value between the acetal proton and methyl carbon and the 1JC,H value of the acetal carbon. The values,.of these parameters were all somewhat related to ring-size; the 2JC,H value was most closely related. The sign of 2JC,H was shown to be positive for 2-methy l-l,3-dioxolane and Z-methy l-l,3-dioxane by means of selective population transfer experiments. Comparison of the 13C NMR chemical shifts of the acetal with the parent diol was found to give information about acetal location.

Preparation of glucosidic derivatives of steganol.

Glucoside derivatives of steganol analogous to the semisynthetic podophyllotoxin derivative, VP 16-213, were prepared. Glucosidation of steganol with 2, 3, 4, 6-tetra-O-benzylglucopyranose gave the alpha-anomer of the glucoside as the major product. Subsequent removal of the benzyl groups and reaction with acetaldehyde dimethyl acetal gave the ethylidene derivative 10. The beta-anomer of the glucoside was similarly converted to 12. All derivatives prepared were screened for activity in the DNA breakage assay.

ChemInform Abstract: ETHYLIDENE DERIVATIVES OF D‐ERYTHROSE. PART II. SYNTHESIS OF 2,3‐O‐ETHYLIDENE‐β‐D‐ERYTHROFURANOSYL 2,3‐O‐ETHYLIDENE‐β‐D‐ERYTHROFURANOSIDE, A NONREDUCING, TETROSE DISACCHARIDE

Chemischer InformationsdienstVolume 14, Issue 5 Natural Products ChemInform Abstract: ETHYLIDENE DERIVATIVES OF D-ERYTHROSE. PART II. SYNTHESIS OF 2,3-O-ETHYLIDENE-β-D-ERYTHROFURANOSYL 2,3-O-ETHYLIDENE-β-D-ERYTHROFURANOSIDE, A NONREDUCING, TETROSE DISACCHARIDE J. W. VAN CLEVE, J. W. VAN CLEVESearch for more papers by this author J. W. VAN CLEVE, J. W. VAN CLEVESearch for more papers by this author First published: February 1, 1983 https://doi.org/10.1002/chin.198305326AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue5February 1, 1983 RelatedInformation

Studies related to the structures of the olivanic acids MM 13902, MM 4550 and MM 17880 : Three β-lactam antibiotics from streptomyces olivaceus

MM 13902, a β-lactam antibiotic isolated from Streptomyces olivaceus, has been identified as ( 5R6R)- 3- [( E)- 2- acetamidoethenylthio]- 6- [( S)- 1- hydroxysulphonyloxyethyl]- 7- oxo- 1- azabicyclo [3.2.0] hept- 2- ene- 2- carboxylic acid ( 2) by chemical and spectroscopic studies. The related olivanic acids MM 4550 and MM 17880 have been shown to be the corresponding 3- [( E)- 2- acetamidoethenylsulphinyl]- and 3- (2- acetamidoethylthio)- derivatives ( 1 and 5), respectively. A number of carboxylate and sulphate esters of 1, 2 and 5 have been prepared. A key reaction in the characterisation of 2 was the oxidative degradation of its C-2 monomethyl ester ( 12) in dimethylsulphoxide to methyl 3 -[( E)- 2- acetamidoethenylthio]- 5- [( 1R,2S)- 1- carboxy- 2- hydroxysulphonyloxyprop- 1- yl]pyrrole- 2- carboxylate ( 22). The configuration of the C-6 substituent of 2 was determined by a stereospecific elimination reaction of its ethyl sulphate, p-nitrobenzyl carboxylate ( 19) to yield the 6- ( E)- ethylidene derivative ( 32). MM 13902 was oxidised to MM 4550 with m-chloroperbenzoic acid.

Reaction of grayanotoxin-II with lead tetraacetate.

The 3, 6-diacetate (3) of grayanotoxin-II (1), a diterpene isolated from Leucothoe grayana, was treated with lead tetraacetate to afford 1, 3, 6-triacetyl-1 (R), 6 (R)-grayanol (4.) The structure of 4 was established by spectroscopic means and X-ray analysis of the ethylidene derivative (5). Alkaline hydrolysis of 4 gave a ketal (7).

Conversion of sugar 1,2-thioorthoesters to bicyclic 1,2-orthoesters

1. The synthesis of some 1,2-0-(1-ethylthio- and p-tolylthio) ethylidene derivatives of D-glucose and L-rhamnose was described. 2. The reaction of sugar thioorthoesters with monosaccharide derivatives, containing one hydroxyl group, in the presence of mercury salts and an organic base, gives bicyclic sugar orthoesters.

Carbon‐13 and proton magnetic resonance spectra of 2,4‐disubstituted 3,3‐diphenyltetrahydrofurans derived from isomethadone and isomethadol

AbstractProton and carbon‐13 nmr spectra for cis‐ and trans‐2‐ethyl‐3,3‐diphenyl‐4‐methyltetrahydrofurans and 2‐ethylidene‐3,3‐diphenyl‐4‐methyltetrahydrofuran, derived from the pyrolysis of the quaternary ammonium salts of the diastereomeric isomethadols and isomethadone, respectively, are reported. 1H and 13C chemical shifts and 1H‐1H coupling constants have been assigned in each case. The isomeric teterahydrofurans have been analyzed in terms of a half‐chair conformation, and an envelope conformation for the ethylidene derivative.

1,2( R):5,6( R)-, 1,2( R):5,6( S)-, and 1,2( S):5,6( S)-bis- O-(trifluoromethyl)-ethylidene- D-mannitol

The three possible 1,2:5,6-bis- O-(trifluoromethyl)ethylidene- D-mannitols have been isolated from the reaction between D-mannitol and 1,1,1-trifluoroacetone, and converted into 2,3- O-(trifluoromethyl)ethylidene derivatives of D-glycerol and D-glyceric acid. The assignment of configuration to the acetal carbon atom in the various products was based on n.m.r. studies. Chemical shift non-equivalence is exhibited by the acetal methyl group in 2,3- O-( S)-(trifluoromethyl)ethylidene- D-glycerol ( RS)-atrolactate ( i.e., where the atrolactoyloxymethyl substituent is cis to the acetal methyl group), whereas the corresponding 2,3- O-( R)-trifluoromethyl)-ethylidene- D-glycerol derivative shows only a single methyl signal.

602. Ethylidene derivatives of mannitol

602. Ethylidene derivatives of mannitol

Ethylidene derivatives of sorbitol.

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