Enantiodivergent Synthesis Research Articles

Enantiodivergent Synthesis of Either Enantiomer of ABCDE-Ring Analogue of Antitumor Antibiotic Fredericamycin A via Intramolecular [4 + 2] Cycloaddition Approach

[reaction: see text] An intramolecular enantiodivergent synthesis of both enantiomers of the ABCDE-ring analogue 22 of fredericamycin A is reported. Key steps involve an intramolecular [4 + 2] cycloaddition of 17 and an aromatic Pummerer-type reaction of 19. A lipase-catalyzed enantioselective desymmetrization of prochiral diol 2 using 1-ethoxyvinyl 2-furoate 3 led to the pivotal intermediate (R)-4.

ChemInform Abstract: Reversal of Stereoselectivity in [5 + 2] Pyrone—Alkene Cycloadditions Using a Sulfoxide‐to‐Sulfoximine Switch. Enantiodivergent Synthesis of 8‐Oxabicyclo[3.2.1]octane Systems.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reversal of stereoselectivity in [5 + 2] pyrone--alkene cycloadditons using a sulfoxide-to-sulfoximine switch. Enantiodivergent synthesis of 8-oxabicyclo[3.2.1]octane systems.

[reaction: see text] Switching from a sulfinyl to a sulfonimidoyl group allows the reversal of the sense of asymmetric induction in thermal [5C + 2C] intramolecular pyrone-alkene cycloadditions. Removal of the sulfoximine unit from the resulting cycloadducts yields optically active oxabicyclic systems that are enantiomeric to those obtained using the sulfinyl chiral auxiliary.

Facile and Stereoselective Synthesis of Non-Racemic 3,3,3-Trifluoroalanine

A highly stereoselective enantiodivergent synthesis of non-racemic 3,3,3-trifluoroalanine 7 is reported. The methodology is based on the reduction, by 9-BBN or DIBAH, of the chiral sulfinimine 3 derived from ethyl trifluoropyruvate, followed by acidic hydrolysis of the resulting diastereomeric sulfinamides 4 and 5.

ChemInform Abstract: Dynamic Kinetic Resolution of Bis‐sulfinyl Chlorides: A General Enantiodivergent Synthesis of C2‐Symmetric Bis‐sulfinate Esters and Bis‐sulfoxides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantiodivergent syntheses of cycloheptenone intermediates for guaiane sesquiterpenes

The syntheses of enantiomeric 6-isopropenyl-3-methyl-2-cycloheptenones 16 and 22 have been effected starting from ( R)-(−)-carvone. In the synthesis of 16, ( R)-(−)-carvone was reduced and the resulting dihydrocarvone transformed regioselectively into silyl enol ethers. Cyclopropanation with dibromocarbene and in situ rearrangement gave an α-bromo-cycloheptenone which was reduced to the ( R)-(+)-cycloheptenone 16. In the synthesis of 22, ( R)-(−)-carvone was cyclopropanated with a sulfur ylide, followed by reduction with LiAlH 4 and acid-catalyzed cyclopropylcarbinyl rearrangement to afford a cycloheptenol. Oxidation and double bond conjugation led to the ( S)-(−)-cycloheptenone 22 in a partially racemized form. Four cycloheptenones have been obtained and are suitable intermediates for the enantiodivergent syntheses of guaiane sesquiterpenes.

Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (−)-Geissman-Waiss lactone

The diastereofacial selectivity of enecarbamates bearing a chiral auxiliary was evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeric azacyclobutanones derived from the 8-phenylmenthyl enecarbamate permitted an enantiodivergent synthesis of the (−)-Geissman-Waiss lactone, a key intermediate in the synthesis of necine bases.

ChemInform Abstract: Enantiodivergent Synthesis of Both Enantiomeric Forms of Substituted Paraconic Acids Starting from D‐Mannitol as a Chiral Pool.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

( S)-(−)-α-Methylbenzylamine as an efficient chiral auxiliary in enantiodivergent synthesis of both enantiomers of N-acetylcalycotomine

( S)-(−)-α-Methylbenzylamine 2 was used as a chiral auxiliary in the enantiodivergent synthesis of simple isoquinoline alkaloids. The prochiral imine moiety in compound 4 was reduced with different reagents, giving diastereomeric amines 5a or 5b, which subsequently were transformed to either ( S)-(−)- N-acetylcalycotomine 6 or ( R)-(+)- N-acetylcalycotomine ent- 6 in good enantiomeric excess. 19F NMR of its Mosher's acid ester was used to establish the purities of final compounds.

Enantiodivergent synthesis of both enantiomeric forms of substituted paraconic acids starting from d-mannitol as a chiral pool

Abstract Acetamide-acetal Claisen rearrangement of the C2-symmetric enediol easily derived from d -mannitol provided a chiral C8-building block, which was demonstrated to be versatile for divergent synthesis of both enantiomeric forms of substituted paraconic acids.

Chiral Carbocyclic Nucleosides from d-Glucose: Enantiodivergent Synthesis and One-Pot Entry of Dimethylamino Functionality in the Purine Rings

Cyclization of appropriately designed enose−nitrones derived from d-glucose, having nitrone at C-5 or C-1 and allylic/homoallylic functionalities at C-3 of the sugar backbone, afforded polyhydroxylated aminocarbocycles which were subsequently used as the precursors for carbocyclic nucleoside analogues (11, 13, 16, 21, and 23). The enantiodirecting synthesis of both the enantiomeric pairs of nucleoside analogues 11 and 13, 21a and 23a, and 21c and 23c, has also been demonstrated by judiciously applying intramolecular nitrone cycloaddition (INC) reaction. An interesting observation was that in the cyclization reaction of pyrimidine ring to purine ring in DMF solvent, the substitution of C-6 chloro group with a dimethylamino functionality also occurred spontaneously under mild condition, though similar reactions are reported to occur at higher temperature. The hydrogen bonding between N-3 of the purine ring and an appropriate hydroxy substituent in the carbocycle seems to play a crucial role in this reaction.

ChemInform Abstract: Enantiodivergent Synthesis of the Key Intermediate for a Marine Natural Furanoterpene by Chemoenzymatic Process.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Highly Stereoselectivetrans Addition of π-Type Nucleophiles to a BicyclicN-Acyliminium Ion – Application to the Synthesis of Indolizidine and Pyrrolizidine Alkaloids

Enantiopure bicyclic 5-ethoxytetrahydropyrrolo[1,2-c]oxazol-3-one 1b was prepared in two steps from the known tosylate 4, which is readily available from (S)-pyroglutamic acid. Trapping of the N-acyliminium ion (I), generated in situ from 1b in the presence of Lewis acid, with various silylated π-type nucleophiles gave rise selectively to trans adducts 2. The usefulness of this stereoselective access to trans-2,5-disubstituted pyrrolidines was illustrated by formal syntheses of 3,5-disubstituted indolizidine toxins, starting from 5-allyltetrahydropyrrolo[1,2-c]oxazol-3-one 2a. Moreover, an enantiodivergent synthesis of the pyrrolizidine alkaloids (+) and (–)-xenovenine was achieved starting from the same chiral building block 2a.

Enantiodivergent synthesis of the key intermediate for a marine natural furanoterpene by chemoenzymatic process

A short chemoenzymatic route to both enantiomers of the key intermediate in the preparation of a marine natural furanoterpene was developed by employing a prochiral malonate derivative as a starting material.

ChemInform Abstract: Formal Desymmetrization by a “Mitsunobu Trick” — Enantiomerically Pure cis‐3,4‐Dihydroxypyrroline N‐Oxides for the Enantiodivergent Synthesis of Trihydroxyindolizidines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantiodivergent Synthesis of (R)- and (S)-Rolipram

Both enantiomers of rolipram (1) have been prepared in large quantity from a common intermediate rac-3-(3’-cyclopentyloxy-4’-methoxy)phenyl-4-nitro butyric acid (6), which was resolved by way of the two readily separable diastereoisomeric amides obtained with (S)-(-)-phenylethylamine. Reduction of the nitro group and intramolecular transamidation gave (R)-(-)-1 and (S)-(+)-1, respectively. CD spectra of both enantiomers of rolipram are reported and discussed. Both enantiomers of rolipram presented the same potency of inhibitory activity against recombinant cyclic-AMP-selective phosphodiesterase (PDE4) subtypes.

Formal Desymmetrization by a “Mitsunobu Trick” − Enantiomerically Purecis-3,4-DihydroxypyrrolineN-Oxides for the Enantiodivergent Synthesis of Trihydroxyindolizidines

A protocol is presented for a completely enantioselective formal desymmetrization of Cs-symmetric diols by monoprotection of the corresponding enantiopure C2 diols, followed by an inversion of configuration by a Mitsunobu reaction (“Mitsunobu trick”). Its application to the unprecedented synthesis of enantiopure cis-3,4-dihydroxypyrroline N-oxides, employed in the enantiodivergent synthesis of two selectively protected 1,2,7-trihydroxyindolizidines, is also reported.

Absolute Configuration of (+)-PT-Toxin: Enantiodivergent Synthesis of (+)- and (-)-PT-Toxins

Absolute Configuration of (+)-PT-Toxin: Enantiodivergent Synthesis of (+)- and (-)-PT-Toxins

ChemInform Abstract: Bicyclo(3.3.1)nonanes as Synthetic Intermediates. Part 21. Enantiodivergent Synthesis of the cis,cis 2,6‐Disubstituted Piperidin‐ 3‐ol Chiral Building Block for Alkaloid Synthesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Enantiodivergent Synthesis of a Decalin Type of Chiral Building Blocks and Their Application to Terpenoid Synthesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.