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Reductive lithiation and cyclization of N-Boc α-amino nitriles are often highly stereoselective. The alkyllithium intermediates are formed with varying levels of selectivity, but the alkyllithium geometry does not play a major role in the overall stereoselectivity. The final configuration is determined in the cyclization reaction, where both retention and inversion pathways are observed. Where strong thermodynamic preferences exist in the products, the kinetically controlled alkyllithium cyclization favors the more stable product.

Transformation of 1-hydroxy-1-phenylpentan-2-one and 1-hydroxy-3-methyl-1-phenylbutan-1-one results in complex reaction mixtures.Chiral substrates (IV) react with the inversion of the stereocenter.

The reaction proceeds via a gold-catalyzed cyclization step and [3,3]-sigmatropic rearrangement with formal inversion of the allylic moiety.

Deprotonation of N-vinyl ureas carrying an N-aryl substituent with strong bases leads to migration of the N-aryl group from N to C.

The ruthenium catalyst generated in situ from H2Ru(CO)(PPh3)3, (S)-SEGPHOS, and a TADDOL-derived phosphoric acid (TPA) promotes butadiene hydrohydroxyalkylation to form enantiomerically enriched products.

C3 symmetric chiral trimethylsumanene was enantioselectively synthesized through Pd-catalyzed syn-selective cyclotrimerization of an enantiomerically pure iodonorbornenone, ring-opening/closing ole...

Diastereomeric mixtures of N-phenylisoxazolines (III) and (IV) are formed due to high inversion energy barrier of the nitrogen.

The helical organization of cholesteric liquid crystals is omnipresent in living matter. Achieving control over the structure of the cholesteric helix consequently holds great potential for developing stimuli-responsive materials matching the level of sophistication of biological systems. In particular, inversion of a cholesteric helix is associated with inversion of the circular polarization of the light it reflects. While control over the cholesteric period has been thoroughly investigated, reports on helix inversion are scarcer. Predicting which systems display helix inversion also remains a challenge because of the subtle balance of contributions underlying this phenomenon. Here we provide an overview on recent advances in controlling and understanding helix inversion in cholesteric liquid crystals.

A new stereoselective cyclization that provides enantiopure 2,3-methanopyrrolidines from zincated α-N-homoallylamino nitriles occurs with a stereospecific inversion of the homoallylic stereogenic center.

A concise synthesis of β-D-fructofuranosyl α-D-galactopyranoside (2), and β-D-fructofuranosyl α-D-mannopyranoside (3) is described. Inversion of the C-3 α-hydroxy group of α-D-galactopyranosyl and α-D-mannopyranosyl β-D-psicofuranosides 10 and 11 via oxidation and stereoselective reduction furnished the corresponding β-D-fructofuranosides in excellent yields.

The reactions of (Rp)-menthyloxymethyl-phenylphosphine-borane with several organolithium reagents are described. Less sterically hindered reagents such as m-anisyllithium and p-anisyllithium react with the phosphine-borane to afford the corresponding substitution products with high stereochemical integrity with inversion of configuration. On the other hand, o-substituted phenyllithiums lead to products possessing very low optical purities.

The kinetic products derived from addition of phthalimide, N-methyltoluenesulfonamide, or benzenethiol to homochiral Fp(dioxene)BF 4 salts [Fp=CpFe(CO) 2 ] undergo unimolecular dyotropic rearrangement, resulting in inversion of the two initially formed asymmetric centers

A facile synthesis of secondary amines from alcohols is reported with N-methyltri-fluoromethanesulfonamide ( 2 ) in the Mitsunobu reaction. The reaction was demonstrated to proceed with inversion of configuration and provided a convenient synthetic route to the (R,R) and (S,S)-enantiomers ( 24 and 25 ) of the antitumor polyamine 1 by utilizing either (R)- or (S)-3-(N-methyltrifluoromethanesulfonamido)butan-1-ol ( 21 or 22 ) and 1,7-bis-(trifluoromethanesulfonamido)heptane ( 33 ). Reagents 21 and 22 were prepared from commercially available (S)- and (R)-1,3-butanediol, respectively.

The first examples of a new class of main group metallacycles, stibathiolanes, have been synthesized via transmetalation from ziconocene metallacycles. The x-ray crystal structures of three 1-halostibathionaes have been determined and the compounds found to be polymeric in the crystalline state. Physical and spectroscopic data indicate that the compounds are monomeric in hydrocarbon solution but that they undergo rapid-reversible halide-exchange reactions. A consequence of one of these exchange reactions is the inversion of stereochemistry at antimony. The processes have been investigated by using a variety of NMR and crossover experiments. The proposed intermediate for the inversion of stereochemistry at the metal center is supported by the solid-state structures of the compounds in which the proposed connectivity of the intermediate is crystallographically established.

Pharmacological considerations prompted the authors to synthesize a series of 8-hydroxylated optically active derivatives of diazabicyclo[4.3.0]nonanes and of their 2,5-dioxo analogs from trans-4-hydroxy-L-proline. Esterification with appropriate anhydrides led to the corresponding esters with 6S,8R configuration. Inversion of configuration at C-8 was performed using Mitsunobu method and led to the diastereoisomeric series of 6S,8S esters. A tentative pharmacological evaluation was carried out in the area of sedative and spasmolytic activities.

The natural alkaloid cryptaustoline is (13R,7S)-(−)-1 due to the heretofore unprecedented inversion while the formamidine route led to the expected (13S,7R)-(+)-1

Acid-catalysed cyclisation of substituted 1,6- or 1,4-alkane diols with suitably placed phenylthio groups leads to high yields of tetrahydropyrans formed by exo or endo hydroxyl participation during phenylthio migration with inversion at both the migration origin and terminus.

(S)-(+)-N,N'-Dicyclohexyl-O-(1-methylheptyl)isourea [(S)-2] reacts with acetic acid in cyclohexane to give (R)-(-)-(1-methylheptyl) acetate [(R)-3] with 100% inversion of configuration. Reaction of isourea (R)-2 with phenol proceeds also with inversion of configuration (99.8%) yielding (S)-(+)-(1-methilheptyl) phenyl ether [(S)-4] as the main product; optically active 2- and 4-(1-methylheptyl)phenols [(S)-5] and [(S)-6], respectively, are formed simultaneously

2,6-Dideoxy-2-fluoro-α-L-talopyranose has been prepared as its triacetate from inexpensive D-fructose by head-to-tail inversion.

The asymmetric synthesis of (S)-(+)-cryptaustoline was accomplished and found to differ in sign of rotation with the natural «S»-(-)-material. The previously assigned absolute configuration was found to be incorrect and is now corrected. The reversal in stereochemistry came about through an unusual manner involving (S)-(+)-laudanosoline (3) cyclizing to (R)-(-)-cryptaustoline ((-)-1c). The mechanism was explored by oxidation of a series of deuterio derivatives of laudanosoline, all of which retained deuterium in the resultant cryptaustoline

The development of novel, mild inversion chemistry which facilitates the preparation of the 13-epi-22,23-dihydroavermectin B 1 aglycone 1 is described.

The stereochemistry of the intramolecular substitution of phenylselenonyl group by a nitrogen atom in tosylamino group was proved to be inversion by the oxidative cyclization of (S)-1-alkyl-4-(tosylamino)butyl phenyl selenides to (R)-N-tosyl-2-alkylpyrrolidines.