Construction of Spiro[pyrrolidine‐3,3′‐oxindoles] − Recent Applications to the Synthesis of Oxindole Alkaloids

Secondary metabolites of fungi from marine habitats.

Following the feeding of a triacylglycerol-rich meal to healthy adult human beings, duodenal contents were aspirated for ex vivo chemical and physical-chemical analyses. The aspirates were collected during established lipid digestion and absorption into a "cocktail" of chemical inhibitors that rapidly inhibited ex vivo lipolysis. Following ultracentrifugation, the lipids separated into a floating oil layer, several interfacial layers, a "clear" or turbid "subphase", and a precipitated "pellet". By chemical and phase analyses, the floating layer was composed of oil-in-water emulsion particles with cores of triacylglycerol (TG), diacylglycerols (DG), and cholesteryl esters (CE) emulsified with a surface coat of partially ionized fatty acids (FA), monoacylglycerols (MG), diacylphosphatidylcholine (PL), and bile salts (BS). The interfacial layers contained similar emulsion particles dispersed among excess emulsifier which adopted a lamellar liquid-crystalline structure. Precipitated pellets were composed principally of emulsifying lipids, with smaller amounts of crystalline calcium soaps and BS. Relative lipid compositions of all but three subphases fell within a two-phase region of the condensed ternary phase diagram (Staggers et al., 1990, companion paper) where saturated mixed micelles composed of BS, FA "acid-soaps", MG, PL, cholesterol (Ch), and traces of DG (and TG) coexisted with unilamellar liquid-crystalline vesicles composed of the same lipids. Attempts to achieve clean separation of vesicles from micelles by repeat ultracentrifugation failed. Compared with the structure and sizes of lipid particles in equilibrated model systems (Staggers et al., 1990), quasielastic light scattering (QLS) analysis revealed that ex vivo micellar sizes (mean hydrodynamic radii, Rh) were similar (less than or equal to 40 A), whereas unilamellar vesicle sizes (Rh = 200-600 A) were appreciably smaller. Two-component QLS analysis of the subphases showed that much larger proportions of lipids were solubilized by micelles than were dispersed as unilamellar vesicles. When followed as functions of time, vesicles frequently dissolved spontaneously into mixed micelles, indicating that, in the nonequilibrium in vivo conditions, the constituent micellar phase was often unsaturated with lipids. These results are consistent with the hypothesis that, during hydrolysis of emulsified DG and TG by luminal lipases, unilamellar vesicles originate in lamellar liquid crystals that form at emulsion-water interfaces in the upper small intestine. In a BS-replete environment, unilamellar vesicles probably represent the primary dispersed product phase of human fat digestion and facilitate the dissolution of lipolytic products into unsaturated mixed micelles.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical-chemical behavior of dietary and biliary lipids during intestinal digestion and absorption. 2. Phase analysis and aggregation states of luminal lipids during duodenal fat digestion in healthy adult human beings

2.1.5. Electrophilic Attack on CdC 3994 2.1.6. NH Insertions in Diazo Compounds 3994 2.1.7. Pd Catalyzed Cyclizations 3994 2.2. Cyclizations by C-C Bond formation 3995 2.2.1. Nucleophilic Displacement of Halides 3995 2.2.2. Cyclizations Involving CdO Group 3995 2.3. Cycloadditions 3996 2.4. Ring Rearrangements 3997 2.4.1. Rearrangements of Four-Membered Rings 3997 2.4.2. Rearrangements of Larger Rings 3998 2.5. Reduction of Azetidin-2-ones 3998 2.6. Miscellaneous Syntheses 3999 2.7. Important Classes of Compounds 4000 2.7.1. Natural Products 4000 2.7.2. Azetidine Carboxylic Acids 4001 2.7.3. Exomethylene Azetidines 4002 2.7.4. Ligands for Metal-Catalyzed Reactions and Chiral Auxiliaries 4003

Novel syntheses of azetidines and azetidinones.

Renaissance of annulene chemistry.

Some steroidal analogues embodying the hitherto unknown 13(148)-abeo skeleton have been synthesized by Fe(II)-induced rearrangement (tandem β-fission/reductive alkylation) of 14α-hydroperoxy-7-en-6-ones. The configurational assignment was made by thorough analysis of NMR spectra; the structure of one of the products was unambiguously assessed by X-ray single-crystal analysis.

Fe(II)‐Induced Fragmentation Reaction of γ‐Hydroperoxy‐α,β‐enones. Part 1. Synthesis of 13(14→8)‐abeo‐Steroids

Carbon-13 NMR study on the nature of resonance interactions in 4-substituted benzonitriles, acetophenones, and methyl benzoates

Cristallisation dans I2/c avec Z=4; affinement jusqu'a R=0,067. Le pigment de la bile est sous forme de sel et sa conformation est stabilisee par liaisons hydrogene intra- et intermoleculaires avec le cation ammonium et les molecules de chloroforme. Les angles de torsion dans les chaines propioniques sont tres differents de ceux trouves dans la bilirubine elle-meme et dans les derives apparentes

http://journals.iucr.org/c/issues/1983/09/00/a22696/a22696.pdf

Structure of bilirubin IXα (isopropylammonium salt) chloroform solvate, C33H34N4O62−.2C3H10N+.2CHCl3

BILIRUBIN is the end product of haem breakdown in the reti-culoendothelial system1–3 and is excreted into the bile after conjugation with various carbohydrates1,3,4 and polypeptides5. Because of low solubility in aqueous media6 (due to strong intramolecular hydrogen bonds7–12), almost all of the uncon-jugated bilirubin occurring in the circulating blood is tightly but reversibly bound to serum albumin13,14. In the liver cell the pigment is also thought to exist associated with soluble cyto-plasmic proteins functioning as intracellular carriers15–17. Binding of bilirubin to albumin seems to occur through formation of salt linkages and hydrogen bonds18; charged residues of histidine, arginine and tyrosine are involved in the binding19 and at least one lysine group is in or close to the primary binding site20. However, the crystal structure of the pigment11,12 shows the presence of only intramolecular hydrogen bonds (four NH … O and two OH … O bonds). Thus the introduction of an amino group-bearing compound in the crystal should provide a useful model of the binding of bilirubin to albumin and other proteins. We report here the X-ray crystal structure of a molecular complex of bilirubin (Fig. 1) with isopropyla-mine and chloroform. This complex is a salt of bilirubin through the carboxyl groups, that is, the di-isopropylammonium bilirubinate with two chloroform molecules of crystallisation (Fig. 2). This X-ray analysis represents the first structural description of bilirubin in salt form.

Angelo Mugnoli

Papers

Fe(II)‐Induced Fragmentation Reaction of γ‐Hydroperoxy‐α,β‐enones. Part 1. Synthesis of 13(14→8)‐abeo‐Steroids

Carbon-13 NMR study on the nature of resonance interactions in 4-substituted benzonitriles, acetophenones, and methyl benzoates

Structure of bilirubin IXα (isopropylammonium salt) chloroform solvate, C33H34N4O62−.2C3H10N+.2CHCl3

Structure of di-isopropylammonium bilirubinate

Crystal and molecular structure of 7-methoxycarbonyl-anti-1,6:8,13-dimethano[14]annulene