Oxidative Ring Contraction Research Articles

Biosynthesis of vitamin B 12: Discovery of the enzymes for oxidative ring contraction and insertion of the fourth methyl group

In the vitamin B 12 biosynthetic pathway the enzymes responsible for the conversion of precorrin-3 to precorrin-4 have been identified as the gene products of cobG and cobJ from Pseudomonas denitrificans. CobG catalyzes the oxidation of precorrin-3 to precorrin-3x (a hydroxy lactone) whereas CobJ is a SAM-dependent C-17 methyl transferase and is necessary for ring contraction. A mechanism for ring contraction is proposed.

Anomeric spirohydantoins of mannofuranose: Approaches to novel anomeric amino acids by an oxidative ring contraction

Bromine-induced oxidative ring contraction of an α-amino-δ-lactone gave a mixture of α-aminotetrahydrofurancarboxylic esters which may allow the preparation of stable amino acid derivatives at the anomeric position of mannofuranose. The synthesis of N-phenylhydantoins at the anomeric position of mannofuranose is reported.

Kondensierte Dithiole, III. Synthese von 1,2‐Dithiolo‐furanen

Ring‐Fused 1,2‐Dithioles, III. – Synthesis of 1,2‐Dithiolo‐furansA series of 1,3‐dithiino‐furans 4/9 has been synthesized by starting with the β‐ketoester 5a or the cyclic ketone 5b. The dithiines undergo oxidative ring contraction to give the corresponding 1,2‐dithiolo‐furans 3/14. The ester function of 3h is easily removed to give 2, the oxaanalog of the antibiotic thiolutine. In general, the lactone group is the most sensitive part in compounds 3, 4 and 14. In marked contrast the dithiine 9a is cleaved by amines at the thioketale site forming the tetronic acid derivatives 10a/b.

Novel oxidative ring contraction of dihydroselenopyrans to selenophenes

Oxidation of 3,6-dihydro-2H-selenopyrans with an electron-withdrawing group at the 2 position proceeded via an unprecedented ring-contraction to afford selenophenes.

Kondensierte 1,2‐Dithiole, II. Synthese von Thieno‐1,2‐dithiolen

Ring‐Fused 1,2‐Dithioles, II. — Synthesis of Thieno‐1,2‐dithiolesA series of thieno‐1,3‐dithiines 5 has been synthesized starting with the β‐thioxoester 4. The dithiines undergo oxidative ring contraction to the corresponding thieno‐1,2‐dithioles 6. Analogously, the dithiolo‐dithiines 8 form the 1,2‐dithiolo‐1,2‐dithioles (1,2,4,5‐tetrathiapentalenes) 14 by ring contraction. — The ester function of 6f is easily removed to give 2, the thioanalog of the antibiotic thiolutine.

Kondensierte 1.2‐Dithiole, I. Synthese von Thiolutin und verwandten Verbindungen

Ring‐Fused 1,2‐Dithioles, I. — Synthesis of Thiolutine and Related CompoundsThe 1,2‐dithiolopyrrole 1 (thiolutine) has been obtained on two different routes. Firstly, by synthesis of the dithiolopyrrole 6a and introduction of the acetamino function into compound 6d by nitration followed by ester saponification and decarboxylation. 6d is also available from 9k by oxidative ring contraction which occurs with simultaneous dealkylation of the benzylamino group. Secondly, by synthesis of the dithiinopyrrole 15b and introduction of the acetamino function into compound 15g by Beckmann rearrangement followed by ring contraction.

ChemInform Abstract: Conformational and Steric Requirements of the Side Chain for Sulfur Participation in Benzothiepin Derivatives.

AbstractThe alkylidenebenzothiepins (I) are subjected to oxidative ring contraction, yielding the chloropropylbenzothiophenes (II) after hydrolysis with HCl.

Synthesis of 1,2-benzisothiazoles by the oxidative ring contraction of 2-aryl- and 4-aryl-3,4-dihydro-2H-1,3-benzothiazines

Sodium periodate oxidation of 6,7-dimethoxy-2-aryl-3,4-dihydro-2H-1,3-benzothiazines (1a-e) gave 5,6-dimethoxy-1,2-benzisothiazole (4). The N-substituted analogues (6a-c) and the 4-aryl isomers of the latter (11a, b) furnished 2-substituted 1,2-benzisothiazolidine 1-oxides (7a-c) and their 3-aryl analogues (12a, b), respectively. The observed conversions of the 1,3-benzothiazines to 1,2-benzisothiazole and to 1,2-benzisothiazolidines are new ring transformation reactions of 3,4-dihydro-1,3-benzothiazines, representing a new route for the synthesis of 1,2-benzisothiazoles and their hydrogenated derivatives.

ChemInform Abstract: Oxidative Ring Contraction of Benzeneselenenate Adducts of Glycal Ethers. Synthesis of Showdomycin Analogues.

AbstractThe D‐glucal (I) reacts with benzeneselenenyl chloride (II) to give the adduct (III).

Oxidative ring contraction of benzeneselenenate adducts of glycal ethers. synthesis of showdomycin analogues

Treatment of 3,4,6-tri-O-benzyl-d-glucal (la) first with benzeneselenenyl chloride and then with water and triethylamine gave (10) in 67% yield; the latter compound was treated with m-chloroperbenzoic acid and the putative ring-contracted aldehyde (2a) obtained was converted into the showdomycin analogue (3a) in satisfactory overall yield. 3,4,6-Tri-O-benzyl-d-galactal (14) was similarly converted into the corresponding α-d-lyxoside (16).

Ring Transformations of 1,3 -Benzothiazines, 5 1 synthesis of benzisothiazoles by the oxidative ring contraction of 2-aryl-4 H-and 4-ARYL-2 H-1,3-benzothiazines

6,7-Dimethoxy-2-phenyl-4 H-1,3-benzothiazine ( 1 ¯ ¯ a ¯ ¯ ) was oxidized with hydrogen peroxide to yield [2,2′-bis(benzoylaminomethyl)-4,4′,5,5'-tetramethoxyldiphenyl disulfide ( 4 ¯ ¯ ) . Potassium permanganate oxidation of 1 ¯ ¯ a ¯ ¯ gave 6,7-dimethoxy-2-phenyl-4 H-1,3-benzothiazin-4-one ( 5 ¯ ¯ a ¯ ¯ ) , which was oxidized with the calculated amounts of perbenzoic acid to obtain the corresponding 1-oxide ( 6 ¯ ¯ a ¯ ¯ ) and 1,1-dioxide ( 7 ¯ ¯ ) . Oxidation of 5 ¯ ¯ a ¯ ¯ − c ¯ ¯ with sodium periodate involved ring contraction, affording 1,2-benzisothiazol-3(2 H)-one 1-oxides ( 8 ¯ ¯ a ¯ ¯ − c ¯ ¯ ) . A similar ring transformation was observed in the oxidation of 4-aryl-2 H-1,3-benzothiazines ( 1 ¯ ¯ 3 ¯ ¯ a ¯ ¯ − f ¯ ¯ ) , resulting in the formation of 3-aryl-5,6-dialkoxy-1,2-benzisothiazoles ( 1 ¯ ¯ 4 ¯ ¯ a ¯ ¯ − f ¯ ¯ ) . The assumed mechanism of these ring transformations is discussed. The conversion of 1,3-benzothiazines to 1,2-benzisothiazoles actually represents a ring transformation reaction of 1,3-benzothiazines and a new synthesis of 1,2-benzisothiazole derivatives. The structures of the new compounds were confirmed by ir, 1H and 13C nmr spectroscopy.

Ring transformations of 1,3-benzothiazines, 5 synthesis of benzisothiazoles by the oxidative ring contraction of 2-aryl-4?- and 4-aryl-2?-1,3-benzothiazines

Ring transformations of 1,3-benzothiazines, 5 synthesis of benzisothiazoles by the oxidative ring contraction of 2-aryl-4?- and 4-aryl-2?-1,3-benzothiazines

Mechanism of oxidative ring contraction of monocyclic polyoxoenediols by active manganese dioxide

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Studies related to cyclopentanoid natural products. Part 2. An improved route to (4R)-4-hydroxy-2-hydroxymethylcyclopent-2-en-1-one and its O-substituted derivatives

(3R,4S,5R)-3,4-O-Cyclohexylidene-3,4,5-trihydroxycyclohexan-1-one (11a), prepared from D-quinic acid (4a) by a published three-step sequence, was converted into the 5-O-benzoyl derivative (11b) by the action of benzoyl chloride. Simultaneous protection of the ketonic carbonyl group and removal of the cyclohexylidene moiety occurred when the compound (11b) was treated with ethane-1,2-dithiol and boron trifluoride–diethyl ether. The derived (7R,8R,9R)-9-benzoyloxy-7,8-dihydroxy-1,4-dithiaspiro-[4.5]decane (15a), when treated sequentially with lead(IV) acetate and pyrrolidinium acetate, underwent an oxidative ring contraction to give (8R)-8-benzoyloxy-1,4-dithiaspiro[4.4]non-6-ene-6-carbaldehyde (17a).

ChemInform Abstract: 1H‐NMR CONFORMATIONAL STUDY OF 2‐ACYL‐3,5‐DIALKYLFURANS USING LANTHANIDE SHIFT REAGENTS

Pyrylium salts undergo oxidative ring contraction to 2-acyl-3,5-dialkylfurans II. A systematic 1H-NMR room-temperature study was made for compounds II a-e having methyl and/or ethyl substituents, using Eu(fod), as lanthanide shift reagent. The conformation always is trans (IIB), minimizing steric interactions. Calculations also indicate a preferred planar conformation IIC for the 5-ethyl group. The corresponding oximes III were also studied similarly, but the effects are too complex to be understood at the present stage.

1H‐NMR Conformational Study of 2‐Acyl‐3,5‐dialkylfurans Using Lanthanide Shift Reagents

AbstractPyrylium salts undergo oxidative ring contraction to 2‐acyl‐3,5‐dialkylfurans II. A systematic 1H‐NMR room‐temperature study was made for compounds II a‐e having methyl and/or ethyl substituents, using Eu(fod), as lanthanide shift reagent. The conformation always is trans (IIB), minimizing steric interactions. Calculations also indicate a preferred planar conformation IIC for the 5‐ethyl group. The corresponding oximes III were also studied similarly, but the effects are too complex to be understood at the present stage.

A convergent scheme for the synthesis of spiroketals and the synthesis of (±)-chalcogran

The hetero-Diels-Alder condensation between furanoid and pyranoid exocyclic vinyl ethers establishes the spiroketal system and subsequent oxidative ring contraction leads to 1.6-dioxaspiroalkane carboxylic acids. The latter are useful subunits for polyether antibiotic synthesis.

ChemInform Abstract: A NOVEL SYNTHESIS OF 3,3,5,5‐TETRAMETHYLCYCLOPENTANE‐1,2‐DIONE. AN OXIDATIVE RING CONTRACTION WITH SELENIUM DIOXIDE

Chemischer InformationsdienstVolume 8, Issue 43 Isocyclic Compounds ChemInform Abstract: A NOVEL SYNTHESIS OF 3,3,5,5-TETRAMETHYLCYCLOPENTANE-1,2-DIONE. AN OXIDATIVE RING CONTRACTION WITH SELENIUM DIOXIDE T. SIMONEN, T. SIMONENSearch for more papers by this authorT. LAITALAINE, T. LAITALAINESearch for more papers by this author T. SIMONEN, T. SIMONENSearch for more papers by this authorT. LAITALAINE, T. LAITALAINESearch for more papers by this author First published: October 25, 1977 https://doi.org/10.1002/chin.197743121Read the full textAboutPDF 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue43October 25, 1977 RelatedInformation

ChemInform Abstract: OXIDATIVE RING CONTRACTION OF THE 1,2‐DIHYDRO‐1,3‐DIMETHYL‐2‐OXOPYRIMIDINIUM CATION TO 3‐METHYL‐2,4‐OXAZOLIDINEDIONE

Chemischer InformationsdienstVolume 7, Issue 29 Heterocyclic Compounds ChemInform Abstract: OXIDATIVE RING CONTRACTION OF THE 1,2-DIHYDRO-1,3-DIMETHYL-2-OXOPYRIMIDINIUM CATION TO 3-METHYL-2,4-OXAZOLIDINEDIONE O. S. TEE, O. S. TEESearch for more papers by this authorM. ENDO, M. ENDOSearch for more papers by this author O. S. TEE, O. S. TEESearch for more papers by this authorM. ENDO, M. ENDOSearch for more papers by this author First published: July 20, 1976 https://doi.org/10.1002/chin.197629206Read the full textAboutPDF 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume7, Issue29July 20, 1976 RelatedInformation

Oxidative ring contraction of the 1,2‐dihydro‐1,3‐dimethyl‐2‐oxopyrimidinium cation to 3‐methyl‐2,4‐oxazolidindione

Oxidative ring contraction of the 1,2‐dihydro‐1,3‐dimethyl‐2‐oxopyrimidinium cation to 3‐methyl‐2,4‐oxazolidindione