Palladium(II) and Platinum(II) Polyamine Complexes: X‐Ray Crystal Structures of (SP‐4‐2)‐Chloro{N‐[(3‐amino‐κN)propyl]propane‐1,3‐diamine‐κN,κN′}palladium(1+) Tetrachloropalladate (2–) (2 : 1) and (R,S)‐Tetrachloro[μ‐(spermine)]dipalladium(II) (={μ‐{N,N′‐Bis[(3‐amino‐κN)propyl]butane‐1,4‐diamine‐κN:κN′}}tetrachlorodipalladium)Codina, Gemma; Caubet, Amparo; López, Concepción; Moreno, Virtudes; Molins, Elies
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1025::AID-HLCA1025>3.0.CO;2-1pmid: N/A
The reactivity of the polyamines L, i.e., N‐(3‐aminopropyl)propane‐1,3‐diamine (1), spermidine (=N‐(3‐aminopropyl)butane‐1,4‐diamine; 2), and spermine (=N,N′‐bis(3‐aminopropyl)butane‐1,4‐diamine; 3) vs. palladium(II) and platinum(II) salts is studied. These reactions allowed us to prepare and characterize a wide variety of PdII and PtII complexes containing the polyamines. Compounds of the general formula [MCl(L)]2[MCl4] (L=1; 1a: M=Pd; 1b: M=Pt) or [MCl(L)]Cl (L=1; 1′a: M=Pd; 1′b: M=Pt) were isolated after treatment of K2[MCl4] or cis‐[MCl2(dmso)2] respectively, with 1. The reaction of K2[MCl4] with 2 led to [MCl(L)]2[MCl4] (L=2; 2a: M=Pd; 2b: M=Pt), while that with 3 gave the neutral dinuclear compounds [M2Cl4(L)] (L=3; 3a: M=Pd; 3b: M=Pt). A comparative study of the results obtained in these reactions allowed us to evaluate the influence of i) the number of N‐atoms in the polyamine, ii) their basicity, and iii) the palladium or platinum salt, upon the nature of the final product. Compounds 1a and (R,S)‐3a were characterized by their X‐ray crystal‐structure analysis. Both exhibited the monoclinic crystal system, 1a the space group P21/c, and 3a the space group P21/n.
Hetero‐Diels‐Alder Cycloadditions of α,β‐Unsaturated Acyl Cyanides, Part 4 , Substituent Effects in Reactions with p‐Substituted StyrenesZhuo, Jin‐Cong; Wyler, Hugo
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1122::AID-HLCA1122>3.0.CO;2-Dpmid: N/A
Cycloadditions of α,β‐unsaturated acyl cyanides (=2‐oxonitriles) 1 – 6 to styrene and its p‐substituted derivatives 7a – f,h are of inverse electron demand and provide, under mild conditions, regio‐ and stereoselectively 2‐aryl‐3,4‐dihydro‐2H‐pyran‐6‐carbonitriles 8 – 13, generally in good yield. Rates for the cycloaddition of acryloyl cyanide 1 to p‐substituted styrenes, determined in competition reactions of substrate pairs relative to that of styrene, increase in the order of electron‐donating ability NO2<Cl<H<AcO<Me<AcNH<MeO of the p‐substituent. Linear correlation of log (kX/kH), and σp+ substituent constants (a Hammett‐type plot), gives a reaction constant ρp+ of −1.47±0.17, supporting a concerted mechanism.
Catalytic Enantioselective Hydrosilylation of Ketones with Rhodium‐Phosphite Complexes Containing a TADDOLate and a Dihydrooxazole UnitHeldmann, Dieter K.; Seebach, Dieter
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1096::AID-HLCA1096>3.0.CO;2-Ipmid: N/A
New types of chiral phosphorus/nitrogen ligands, capable of forming six‐membered‐ring metal chelates have been prepared from α,α,α′,α′‐tetraaryl‐1,2‐dioxolane‐4,5‐dimethanols (TADDOLs), PCl3, and dihydrooxazole alcohols (from amino acids) (7 in Scheme 1). The X‐ray crystal structure of a Rh complex of one of these ligands, 8b, has been determined (Scheme 2 and Fig.). Enantioselective hydrosilylations of dialkyl and aryl alkyl ketones with Ph2SiH2/0.01 equiv. RhI⋅7 have been studied and found to provide secondary alcohols in enantiomer ratios of up to 97 : 3 (Scheme 3 and Table). The ligand prepared from (R,R)‐TADDOL and the (R)‐valine‐derived (R)‐α,α‐dimethyl‐4‐isopropyl‐4,5‐dihydrooxazole‐2‐methanol gives better results than the (R,R,S)‐isomer (7d vs. 7c in Scheme 3), and an i‐Pr group on the 4,5‐dihydrooxazole ring gives rise to a slightly better selectivity than a Ph group. With the (R,R,R)‐ligands the hydrogen transfer occurs from the Re face of the oxo groups (Scheme 4).
Inhibition of Cellobiohydrolases from Trichoderma reesei. Synthesis and Evaluation of Some Glucose‐, Cellobiose‐, and Cellotriose‐Derived Hydroximolactams and ImidazolesVonhoff, Stefan; Piens, Kathleen; Pipelier, Muriel; Braet, Christophe; Claeyssens, Marc; Vasella, Andrea
doi: 10.1002/(SICI)1522-2675(19990707)82:7<963::AID-HLCA963>3.0.CO;2-Vpmid: N/A
The lactam 16, the hydroximolactams 8, 20, 23, and 27, and the imidazole 32 were prepared following known methods. They were tested together with the known tetrazole 35 and the hydroximolactams 2 and 36 as inhibitors of the cellobiohydrolases Cel7A and Cel6A from Trichoderma reesei. Cel7A is only weakly inhibited by these compounds. Comparing their inhibitory activity evidences the importance of occupying subsites +1 and +2. The results strongly suggest that the shape of none of the variants of the lactone‐type inhibitor motif embodied by these inhibitors is complementary to the subsite −1, i. e., analogous to the transition state. Cel6A is rather strongly inhibited by the cellobiose analogues 20, 23, and 32, and by the cellotriose analogue 27. Their relative inhibitory activities evidence that binding at subsite −2 depends upon the shape of the moiety occupying subsite −1. There is only a small difference between the inhibition by the hydroximolactams 20 and 23, which may be (partially) protonated by the catalytic acid of either anti‐ or syn‐protonating glycosidases, and the imidazole 32, which can only be protonated by anti‐protonating glycosidases. The results strongly suggest that shape requirements must be met by glycosidase inhibitors before they can be used to characterize the proton trajectory of glycosidases.
(±)‐1‐[(1R*,2R*,8aS*)‐1,2,3,5,6,7,8,8a‐Octahydro‐1,2,8,8‐tetramethylnaphthalen‐2‐yl]ethan‐1‐one: Isolation and Stereoselective Synthesis of a Powerful Minor Constituent of the Perfumery Synthetic Iso E Super®Nussbaumer, Cornelius; Fráter, Georg; Kraft, Philip
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1016::AID-HLCA1016>3.0.CO;2-Ypmid: N/A
(±)‐1‐[(1R*,2R*,8aS*)‐1,2,3,5,6,7,8,8a‐Octahydro‐1,2,8,8‐tetramethylnaphthalen‐2‐yl]ethan‐1‐one (5) was identified as a minor (ca. 5%) but very powerful (5 pg/l (air)) constituent of the important perfumery synthetic Iso E Super®. Its structure was assigned by NMR spectroscopy and established by a stereoselective synthesis starting from α‐ionone (10). Diastereoselective conjugate addition of Me2CuLi to 10 was followed by a haloform reaction, esterification, and isomerization of the C=C bond by treatment with NaOCl (Schemes 3 and 4). The resulting allyl chloride 17 was ozonized and transformed into the trimethyl(vinyl)octahydrocoumarin 20 by diastereoselective Grignard reaction with ethynylmagnesium chloride, and subsequent Lindlar hydrogenation. Ireland‐Claisen rearrangement of 20 followed by methylation with MeLi afforded the target molecule 5 that was identical with the material isolated from commercial Iso E Super®.
Synthesis of (+)‐(S)‐Streptenol A and Biomimetic Synthesis of (2R,4S)‐ and (2S,4S)‐2‐(Pent‐3‐enyl)piperidin‐4‐olDollt, Heribert; Hammann, Peter; Blechert, Siegfried
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1111::AID-HLCA1111>3.0.CO;2-Lpmid: N/A
(+)‐(S)‐Streptenol A is synthesized by coupling a 1,3‐dithiane with an optically pure epoxide. The absolute configuration of (+)‐(S)‐streptenol A is thereby correlated with that of (S)‐malic acid. Stereoselective reduction of an oxime that could easily be prepared from streptenol A gave the (3S,5R)‐ and (3S,5S)‐aminostreptenols, and after cyclization, configurationally pure 2,4‐functionalized piperidine alkaloids.
Ring Contraction of an Ascomycin Derivative to a 19‐Membered MacrolactamZimmer, Reinhold; Baumann, Karl; Sperner, Hildegard; Schulz, Gerhard; Haidl, Ewald; Grassberger, Maximilian A.
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1038::AID-HLCA1038>3.0.CO;2-Ipmid: N/A
Starting from readily available (22R)‐26,33‐bis‐O‐[(tert‐butyl)dimethylsilyl]‐22,22‐O‐dihydroisoascomycin (5), the synthesis of a doubly ring‐contracted ascomycin derivative, the 19‐membered macrolactam 10, is described.
Catalytic Dendrophanes as Enzyme Mimics: Synthesis, Binding Properties, Micropolarity Effect, and Catalytic Activity of Dendritic Thiazolio‐cyclophanesHabicher, Tilo; Diederich, François; Gramlich, Volker
doi: 10.1002/(SICI)1522-2675(19990707)82:7<1066::AID-HLCA1066>3.0.CO;2-Opmid: N/A
Catalytic dendrophanes 9 and 10 were prepared as functional mimics of the thiamine‐diphosphate‐dependent enzyme pyruvate oxidase, and studied as catalysts in the oxidation of naphthalene‐2‐carbaldehyde (4) to methyl naphthalene‐2‐carboxylate (8) (Scheme 1). They are composed of a thiazolio‐cyclophane initiator core with four generation 2 (G‐2) poly(etheramide) dendrons attached. The two dendrophanes were synthesized by a convergent growth strategy by coupling dendrons 11 and 12, respectively (Scheme 2) with (chloromethyl)‐cyclophane 42 (Scheme 5) and subsequent conversion with 4‐methylthiazole (Scheme 7). The X‐ray crystal structures of cyclophane precursors 30 (Scheme 3), 37, and 38 (Scheme 5) on the way to dendrophanes were determined (Fig. 1). The crystal‐structure analysis of the benzene clathrate of 37 revealed the formation of channel‐like stacks by the cyclophane which incorporate its morpholinomethyl side chain and the enclathrated benzene molecule (Fig. 2). The interactions of the enclathrated benzene molecule with the phenyl rings of the two adjacent cyclophane molecules in the stack closely resemble those between neighboring benzene molecules in crystalline benzene (Fig. 3). The characterization by MALDI‐TOF‐MS (Fig. 4), and 1H‐ and 13C‐NMR spectroscopy (Fig. 5) proved the monodispersity of the G‐2 dendrophanes 9 and 10 with molecular weights up to 11500 Da (for 10). 1H‐NMR and fluorescence binding titrations in H2O and aqueous MeOH showed that 9 and 10 form stable 1 : 1 complexes with naphthalene‐2‐carbaldehyde (4) and 6‐(p‐toluidino)naphthalene‐2‐sulfonate (48, TNS) (Tables 1 and 2). The evaluation of the fluorescence emission maxima of bound TNS revealed that the dendritic branching creates a microenvironment of distinctly reduced polarity at the cyclophane core by limiting its exposure to bulk solvent. Initial rate studies for the oxidation of naphthalene‐2‐carbaldehyde to methyl naphthalene‐2‐carboxylate in basic aqueous MeOH in the presence of flavin derivative 6 revealed only a weak catalytic activity of dendrophanes 9 and 10 (Table 3), despite the favorable micropolarity at the cyclophane active site. The low catalytic activity in the interior of the macromolecules was explained by steric hindrance of reaction transition states by the dendritic branches.