Internal Peptide Late‐Stage Diversification: Peptide‐Isosteric Triazoles for Primary and Secondary C(sp3)−H Activation

Secondary C(sp³)?H arylations were accomplished by palladium catalysis with triazoles as peptide bond isosteres. The unique power of this approach is highlighted by the possibility of achieving secondary C(sp³)?H functionalizations on terminal peptides as well as the unprecedented positional‐selective C(sp³)?H functionalization of internal peptide positions, setting the stage for modular peptide late‐stage diversification.     

Substituted Pyrrolo[3,4-<Emphasis Type="Italic">a</Emphasis>]carbazoles from Reactions between 3-(1-Methoxy-vinyl)indoles and Maleimides

Summary. 5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed into the hydroxy derivatives by treatment with H₂SO₄, selectively reduced to the ether by H₂/Pd–C, and in the imide moiety by L-Selectride^?. From the analogous BOC protected indole derivative the parent α,β-unsaturated ketones were obtained, which were transformed into hydroxyimino compounds, and which could be deprotected by heating to the melting point. Deprotection of the tosyl derivatives was not successful. The imide part of the molecule was hydrolyzed using methanolic NaOH. The stereochemistry of all products was elucidated mainly by spectroscopic methods, and compared with results of calculations.     

5-Methylnaioxone and 5-Methylnaltrexone: Synthesis and Pharmacological Evaluation

Starting from 5-methyl-oxycodone ( 6 ), 5-methylnaloxone ( 4 ), and 5-methylnaltrexone ( 5 ) have been prepared in several steps. Both 4 and 5 behaved as partial agonists in the AcOH writhing agonism and antagonism test in mice.     

New Triterpene Saponins from Herniaria glabra

Three new saponins 1–3 were isolated from Herniaria glabra by means of prep. HPLC and TLC. The structures were established mainly by a combination of 2D-NMR techniques (COSY, TOCSY, ROESY, HMQC, and HMBC) as O-α-L -rhamnopyranosyl-(1→4)-O-β-D -glucopyranosyl-(1-→6)-O-[β-D -glucopyranosyl-(1→2)]-β-D -glucopyranosyl medicagen-28-ate (herniaria saponin 4; 1 ), O-β-D -glucopyranosyl-(1→3)-O-α-L -rhamnopyranosyl-(1→2)-O-[β-(3R)-D -apiofuranosyl-(1→3)]-β-D -4-O-acetylfucopyranosyl 3-O-(β-D -glucuronopyranosyl)-16α-hydroxymedicagen-28-ate (herniaria saponin 5; 2 ), and O-α-L -rhamnopyranosyl-(1→4)-O-β-D -glucopyranosyl-(1→6)-O-[β-D -6-O-acetylglucopyra nosyl-(1→2)]-β-D -glucopyranosyl medicagen-28-ate (herniaria saponin 6; 3 ).     

Substituted Pyrrolo[3,4-a]carbazoles from Reactions between 3-(1-Methoxy-vinyl)indoles and Maleimides

5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed into the hydroxy derivatives by treatment with H₂SO₄, selectively reduced to the ether by H₂/Pd–C, and in the imide moiety by L-Selectride^?. From the analogous BOC protected indole derivative the parent α,β-unsaturated ketones were obtained, which were transformed into hydroxyimino compounds, and which could be deprotected by heating to the melting point. Deprotection of the tosyl derivatives was not successful. The imide part of the molecule was hydrolyzed using methanolic NaOH. The stereochemistry of all products was elucidated mainly by spectroscopic methods, and compared with results of calculations.     

Studies on oxidation of ergot alkaloids: oxidation and desaturation of dihydrolysergol—stereochemical requirements

A new method for the oxidation of ergoline alcohols to aldehydes was found (TFFA-DMSO, −78 °C, then DIPEA). Structural features of ergolines required for successful C7-C8 double bond introduction via Polonovski-Potier reaction of respective 6-N-oxides were defined and experimentally confirmed: (i) the presence of electron-withdrawing group at C-8; (ii) trans-diaxial orientation of N6-O and C7-H bonds (both requirements are fulfilled for dihydrolyserg-17-al and its 2,4-dinitrophenyl hydrazone prepared in this work).     

Novel route to styrene/p‐aminostyrene copolymers

A novel route to styrene/p‐aminostyrene copolymers is described that involves the introduction of amino functionality into the structure of pure monodisperse polystyrene. The simple two‐step synthesis involves the introduction of a bromo group into the aromatic ring by electrophilic substitution and then a palladium‐catalyzed reaction with LiN(SiMe₃)₂ followed by an acid and base treatment to release the free amine. All reactions are carried out at room temperature. This approach avoids the difficulties often associated with the preparation of copolymers from incompatible monomers. The technique also gives a product with a precisely known molecular weight and polydispersity, important parameters governing many physical properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1282–1286, 2007