Andrzej Leniewski

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

Abstract ( 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. 19 F NMR of its Moshers acid ester was used to establish the purities of final compounds.

The Thorpe-Ingold Effect in Cyclic Imides. Part III

- Reactivity of phenyllithium with a number of succinimide derivatives were studied. We have shown that the Thorpe-Ingold effect affected both the reaction products distribution and their structures. Regioselectivity of these reactions were rationalized. Structures were confirmed with NMR and crystallographic methods.

The thorpe-ingold effect in glutarimide derivatives. Part II

Differently substituted glutarimides, 3-methylglutarimide (12), 3,3-dimethylglutarimide (14) and 3,3,4,4-tetramethylglutarimide (18) were prepared and their reactivity towards aryllithiums was investigated. The influence of Thorpe-Ingold effect on the distribution of products in tautomeric equilibrium was observed together with a total regioselectivity of the process. For imide (12) only keto amide (13) was isolated. Imide (14) resulted in formation both hydroxy lactam (16) and keto amide (15), and imide (18) gave only hydroxy lactam (24).

Diastereoselective synthesis of some β-carboline derivatives from l-amino acids

Abstract l -Ala and l -Val were used as chiral inductors in a series of reactions in which a Pictet–Spengler cyclization, completed under mild conditions was the key step. Diketopiperazines 7a and 8a having R configuration at the newly created stereogenic center were obtained with good diastereoselectivity due to 1,4-chirality transfer. Surprisingly, l -Pro promoted the formation of the product with S configuration in the predominant diastereomers 9a and 10a.

Synthesis and Structure Determination of Some Monothio- and Dithioimides Derived from Succinic and Glutaric Acids

A series of novel 5-thioxopyrrolidin-2-ones and 6-thioxopiperidin-2-ones was synthesized using Lawessons reagent in thionation of the appropriate imides. The NMR data were determined, and in one case the structure assignment was additionally supported by X-ray crystallography.

Towards Enantioselective Synthesis Of Tryptophan-Derived Alkaloids

Tryptamine was subjected to a series of reactions with derivatives of L-Ala, L-Val that ended with final diketopiperazines 9 and 10, having (R) configuration on the newly created, via 1,4-chirality transfer, stereogenic center. On the other hand, when L-Pro was used the opposite chirality sense was formed at this position.