A synthesis of novel hydroxyethyl‐substituted tri‐ and penta‐hydroxylated spiro[cyclopentane‐indolizidines] has been reported, featuring an interesting lithium diisopropylamide “LDA”‐mediated α‐diallylation and tetrahydrofuran “THF” ring opening in one‐pot procedure as the key transformation. The synthetic sequence explored herein uses an enantiopure tricyclic lactam as a common chiral precursor, prepared on a gram scale from cost‐effective basic reagents. The key steps in this synthetic way included diastereoselective dihydroxylation reaction, ring‐closing ene–ene metathesis, enamine reduction, and finally lactam reduction. These transformations enabled the efficient and stereoselective construction of the ultimate polyhydroxy‐indolizidine scaffolds. As an application, the biological activity of the synthesized spiro‐indolizidines was evaluated against a panel of α‐glucosidases.

A series of novel optically pure aminoindolizidines featuring fused tetrahydro-furan, thiophene, or pyrrole ring were synthesized from the proteinogenic L-glutamic acid as a chiral precursor and a nitrogen atom source. The synthetic sequence employed tricyclic indolizidinols as advanced building blocks, which were prepared on a gram-scale from bioavailable reagents. Key transformations within the used synthetic sequence included diastereoselective Thompson azidation, Staudinger reduction, Jurjew reaction, and highly diastereoselective catalytic hydrogenation. These steps facilitated the efficient and stereoselective synthesis of the ultimate amino- and N-acetylamino-indolizidines.

One of the important properties of molecules in the biological world is their three-dimensional shape. Stereochemistry is precisely that part of chemistry that deals with the study of the three-dimensional arrangements of atoms in molecules and the way in which these atoms interact with each other. For this reason, it is also known as 3D chemistry, where the prefix "stereo" means "three-dimensional". The textbook "Stereochemistry of organic compounds" is primarily intended for undergraduate students, but it can also serve as supplementary material for doctoral students. Its mission is to provide students with basic information about isomerism, chirality, enantiomers and diastereomers, conformational analysis, stereochemistry of cycloalkanes, prostereoisomerism and point groups.

Synthesis of chiral oxacarba-spiroindolizidine tetraols was achieved by alkene cis-dihydroxylation, diol protection, and lactam carbonyl reduction followed ultimately by acetonide deprotection.

Dihydrofuro[2,3-f]indolizidinone obtained from biosourced reagents even at multigram-scale was used as an advanced building-block with up to five points of chemical diversification. This resulted in the sequential synthesis of a series of mono-, di- and tetra-hydroxyfuranoindolizidines belonging to a very scarce and elaborate tetrahydrofuran-fused indolizidine family with up to six controlled stereogenic centers. These sequences include, among others, diastereoselective olefin epoxidation, stereoselective epoxide ring opening into tetrahydrofurantrans-diols, their protection as an ester or acetonide, and lactam carbonyl reduction ultimately followed by acetate or acetonide deprotection.

We describe the screening of a set of cryptopleurine derivatives, namely thienoquinolizidine derivatives and (epi-)benzo analogs with bioactive phenanthroquinolizidine alkaloids that induce cytotoxic effects in the mouse lymphocytic leukemia cell line L1210. We used three variants of L1210 cells: i) parental cells (S) negative for P-glycoprotein (P-gp) expression; ii) P-glycoprotein positive cells (R), obtained by selection with vincristine; iii) P-glycoprotein positive cells (T), obtained by stable transfection with a human gene encoding P-glycoprotein. We identified the most effective derivative 11 with a median lethal concentration of ≈13 μM in all three L1210 cell variants. The analysis of the apoptosis/necrosis induced by derivative 11 revealed that cell death was the result of apoptosis with late apoptosis characteristics. Derivative 11 did not induce a strong alteration in the proportion of cells in the G1, S or G2/M phase of the cell cycle, but a strong increase in the number of S, R and T cells in the subG1 phase was detected. These findings indicated that we identified the most effective inducer of cell death, derivative 11, and this derivative effectively induced cell death in S, R and T cells at similar inhibitory concentrations independent of P-gp expression.

Two crystals of quinolizidine compounds; systematic name: (rac)-(7,8,9,9a)-tetrahydro-4H-thieno[2,3-b]quinolizine-6,10-dione, (I), and (rac)-(9a,10)-10-hydroxy-8,9,9a,10-tetrahydro-4H-thieno[2,3-b]quinolizin-6(7H)-one, (II), have been compared and characterized by single-crystal X-ray diffraction and electronic analysis. N-heterocyclic rings in both structures are not planar and adopt a half-chair conformation. The molecules of (I) are linked via weak C–H···O hydrogen bonds into chains along c axis. While the crystal stacks in compound (II) are formed by strong O–H···O hydrogen bonds the molecules link into infinite zig-zag chains along the b axis. In both crystal structures, π–π stacking and C–H···π interactions are also observed. Calculation of the net atomic charges shows that O atoms in both compounds carry a relatively large negative charges, in comparison with the corresponding H atoms. Crystal, molecular and electronic structures of these compounds, which are influenced by hydrogen-bonded assemblies in the molecular crystals, are discussed in detail.

Enantiopure N ‐benzyl 6‐oxopipecolic acid, obtained from ( S )‐2‐aminoadipic acid, was evaluated under π‐cationic cyclization conditions. If the combination of SOCl 2 /AlCl 3 seems to be superior in terms of the reaction yields, use of PPA, (CF 3 CO) 2 O/BF 3 · Et 2 O, and Eaton's reagent is also very interesting since in addition to the expected keto‐lactam, reduced‐ and oxidized keto‐lactam, enamides and enamidones containing CF 3 CO– residue are isolated. Mechanisms leading to these products as well as the ones resulting from their acidic treatment were proposed and discussed with the help, in some cases, of univocal transformations and X‐ray analysis.

Abstract We report here the crystal and molecular structure of a new chromane-derivative, namely isopropyl( 2R*,3S*,4S*)-4-(benzo[d]thiazol-2-ylamino)-2-hydroxy-2-ethylchromane-3-carboxylate (I), C21H22N2O4S, which crystallizes as racemate in the space group C2/c. Its structure has been solved using X-ray diffraction data obtained at low temperature (100(2) K). In this compound, the chromane moiety consists of a benzene ring fused with a six-membered heterocyclic ring which adopts a distorted half-chair conformation. The molecules are linked by a combination of O-H∙∙∙N and N-H∙∙∙O hydrogen bonds, resulting in a twodimensional network which helps stabilizing the crystal structure of the compound (I). Dihedral angle between the chromane and benzothiazol rings is 80.6(1)0.

The increasing microbial resistance to primary active structures remains alarming and the effort to look for new antibacterial active structures is still of scientific interest. One of the attractive ways to find new active structures is derivatization of well-known natural compounds. Alkaloids are a structurally diverse group of natural products with a wide range of biological effects. Historically, an attempt to increase the antimicrobial activity of alkaloids through chemical modifications has been successful. In this work, 12 new quinolizidine derivatives were synthesized and tested for their antimicrobial activity. The asymmetric synthesis of the benzoanalogue of the phenanthroquinolizidine bioactive alkaloid (−)-cryptopleurine and the epi-benzoanalogues of (−)-(15R)-hydroxycryptopleurine were achieved in six or seven steps starting from available enantiopure (S)-2-aminoadipic acid used as source of chirality as well as nitrogen. The highest antimicrobial activity was observed in the presence of the final saturated structure, the benzoanalogue of naturally occurring plant alkaloid cryptopleurine. It features selective toxicity, and significantly inhibits the growth of G+ bacteria, especially Staphylococcus sp. Tested derivatives have shown only a weak antifungal activity, but partial inhibition has been observed in the case of model yeasts.

Abstract The title compound, C14H20INO, is a molecule with three stereogenic centres. It absolute configuration was derived from the synthesis and confirmed by structure determination (AD, Flack (Parsons’) parameter: 0.031 (8)). The expected stereochemistry of atoms N1 was confirmed to be S, C5 was confirmed to S, C6 was confirmed to R. The central N-heterocyclic ring is not planar and adopts a half-chair conformation. A calculation of least-squares planes showed that these rings are puckered in such a manner that the five atoms: C5, C6, C7, C12 and C13 (the second ring: C1, C2, C3, C4, C5 and N1) are planar, while atom N1 is displaced from these plane with the out-of-plane displacement of −0.694 (4) and −0.670 (5) Å in the second ring, respectively. Dihedral angle between the planes of the central N-heterocyclic rings is 23.4 (2)°. Crystal structure is also stabilized by C—H···O hydrogen interactions.

We report the crystal and molecular structure of a new isoquinoline-derivative, namely methyl O-[(11R, 11aS)-4-oxo-1, 3, 4, 6, 11, 11a-hexahydro-2H-pyrido[1, 2-b]isoquinolin-11-yl]carbonodithioate (I), C15H17NO2S2, which crystallizes in the non-centrosymmetric space group P212121 and its absolute structure was confirmed by anomalous dispersion effects in diffraction measurements on the crystals. Two central six-membered heterocyclic rings adopt a distorted half-chair conformation. The molecules are linked by a combination of weak C—H∙∙∙O, C—H∙∙∙S, C—H∙∙∙p inter- and intra-molecular interactions resulting in a three-dimensional network in the crystal structure. Crystal Data for C15H17NO2S2 (M =307.41 g/mol): orthorhombic, space group P212121 (no. 19), a = 5.2804(5) Å, b = 8.1347(17) Å, c = 35.015(4) Å, V = 1504.1(4) Å3, Z = 4, T = 298(2) K, μ(MoKα) = 0.354 mm-1, Dcalc =1.358 g/cm3, 20270 reflections measured (5.522° ≤ 2Θ ≤ 50.69°), 2757 unique (Rint = 0.0346, Rsigma = 0.0203) which were used in all calculations. The final R1 was 0.0389 (I > 2σ(I)) and wR2 was 0.0965 (all data).

Abstract We report here the structure of new spiro-derivative, namely methyl (2R,4R)-4-(5-methylthiazol- 2-ylamino)spiro[chroman-2,2’-chromene]-3’-carboxylate, C23H20N2O4S, which crystallizes as racemate in the space group P-1. In this compound, the chromanone moiety consists of a benzene ring fused with a sixmembered heterocyclic ring which adopts a distorted half-chair conformation. The molecules are linked by a combination of N–H⋯N hydrogen bonds and weak C–H⋯O, C-H⋯S, C-H⋯π, inter- and intramolecular interactions resulting in a two-dimensional network in the crystal structure.

The antimicrobial activity of 16 newly prepared quinolizidines derivatives using bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Proteus sp., Escherichia coli) acid fast bacterium Mycobacterium smegmatis, yeasts (Candida albicans, Candida parapsilosis), and filamentous fungi (Fusarium culmorum, Microsporum gypseum, Aspergillus flavus, Botrytis cinerea, Alternaria alternata) was studied in this paper. The best antibacterial properties were demonstrated by derivatives 11Ba, trans10Bb and 11Bb, and the most sensitive microorganism was found to be the gram-positive bacterium S. epidermidis. The derivative 11Bb showed the best antifungal activity, while C. albicans was resistant to all tested derivatives, and C. parapsilosis was fully inhibited in the presence of the derivative 11Ba and 11Bb. Among the filamentous fungi, only the dermatophyte M. gypseum was partially inhibited. Biofilms represent the most prevalent type of microbial growth in nature and are crucial to the development of clinical infections. Newly synthesized derivatives were also added into the medium throughout the biofilm formation. We have observed a significant decrease of biofilm formation in the presence of quinolizidine derivatives, testifying to their significant antimicrobial activity. It seems that the relationship between antimicrobial activity and the structure is based on the alkaline character due to nitrogen, the saturated basic quinolizidine skeleton, and the position of sulfur in the molecule.

Pt(II)-catalyzed carbocyclization of benzaldehyde containing a keto-nitrile functionality resulted in the formation, respectively, of isochromenes and spiro-lactones instead of fused lactams and spiro-lactams as was previously reported. The reaction mechanism was proposed, and the products were identified by multidimensional NMR, IR, and X-ray analysis. The structure of these new products was also confirmed by their synthesis in an unambiguous manner using practical and short approaches.

Abstract The title compound, C13H15NO3S, is a chiral molecule with two stereogenic centres. Its absolute configuration was derrived from the synthesis and confirmed by structure determination. The expected stereochemistry of atoms C5 and C6 was confirmed to be S. The central N-heterocyclic rings are not planar and adopt a half-chair conformation. A calculation of least-squares planes showed that these rings are puckered in such a manner that the five atoms C1, C2, C3, C5 and N1 (second ring: N1, C6, C7, C10 and C11) are planar, while atoms C4 (C5) are displaced from these planes with the out-of-plane displacement of 0.582 (3) Å and 0,666 (2) Å in the second ring, respectively. Dihedral angle between the planes of the central N-heterocyclic rings is 40.0 (1)°. Crystal structure is stabilized by C—H···O hydrogen interactions.

The stereoselective synthesis of epi-thieno analogues of the phenanthroquinolizidine bioactive alkaloids (-)-Cryptopleurine and (-)-(15R)-Hydroxycryptopleurine was achieved in five steps starting from easily available enantiopure (S)-2-aminoadipic acid used as chiral pool and nitrogen atom source. During these investigations, both π-cationic cyclization of chiral N-thienylmethyl-6-oxopipecolinic acids into pure (S)-keto-lactams and theirs regioselective and diastereoselective reduction, considered as key steps of this sequence, were studied. Of particular interest, the Friedel-Crafts cyclization using (CF3CO)2O/BF3·Et2O show that near the expected keto-lactams, enamides and enamidones containing trifluoromethyl residue were isolated. A mechanism leading to the latter products with high synthetic potential was discussed.

Molecules of the title compound, C13H21,NO3, crystallize as single enantiomers with four stereogenic centres, their absolute configuration were confirmed by anomalous dispersion effects determined by diffraction measurements on the crystals. Conformations of the pyrrolidine and 1,3-oxolane rings are close to that of an envelope, with the flap atoms displaced by -0.205 (1) and -0.449 (1) angstrom, respectively, from the plane of the other remaining four atoms. The central six-membered ring of the indolizine moiety adopts a nearly perfect boat conformation, with two atoms displaced by 0.575 (1) and 0.603 (1) angstrom from the plane of the other remaining four atoms. Crystal structure of the title compound is stabilized by C-H center dot center dot center dot O hydrogen interactions.

Abstract The molecules of the title compound, C11H16NS·I, crystallize as single enantiomer with two stereogenic centre, their absolute configuration were confirmed by anomalous dispersion effects in diffraction measurements on the crystals. The conformation of the pyrrolidine ring is close to that of an envelope, with the flap atom N1 displaced by 0.661 (2) A from the plane of the oder remaining four atoms. The central six-membered ring of the indolizine moiety adopt a half-chair conformation with atom C5 displaced by -0.686 (2) Å from the plane of the oder remaining five atoms. The crystal structure of the title compound is stabilized by C-H···I···H-C hydrogen interactions.