Ivar Ugi

The electrophilic substitution of ferrocene by protonated carbonyl compounds

Abstract The α-ferrocenylalkyl caebenium ions are formed from ferrocene and carbonyl compounds in strongly acidic media, in particular mixtures of fluorosulfuric acid and trichloroacetic acid. The α-ferrocenylalkyl carbenium ions are scavenged by nucleophiles or bases. The addition of nucleophiles produces the corresponding α-substituted ferrocenyl alkanes. Proton abstraction by base from the β-position leads to the ferrocenylethene derivatives. Such electrophilic substitutions of ferrocene by carbonyl compounds, followed by suitable scavengeing of the α-ferrocenylalkyl carbenium ion, form the basis of one-pot syntheses of various ferrocene derivatives.

Preparation of 1-ferrocenyl-2-methyl-1-propylamine, a highly effective chiral template in asymmetrically induced synthesis

Abstract The 1-ferrocenyl-2-methyl-1-propylamine ( 2a )is the most effective chiral template in asymmetrically induced peptide synthesis by stereoselective four component condensation (4CC). Two routes for the synthesis of this amine via its N,N-dimethyl derivative ( 12a ) an described. One route involves the conversion of 12a into the corresponding azide 14a by treatment with methyl iodide/sodium azide in diglyme/water and subsequent reduction of the azide. The preferred other route consists of treating 12a with thioglycolic acid/formic acid to yield the carboxymethylmercapto derivative 9a and transformation of the latter into 2a with aqueous ammonia/ammonium chloride/mercuric chloride. Some related reactions are also discussed.

Turnstile Rearrangement and Pseudorotation in the Permutational Isomerization of Pentavalent Phosphorus Compounds

Publisher Summary This chapter deals with turnstile rearrangement and peudorotation in the permutational isomerization of pentavalent phosphorous compounds. The phosphoranes are derivatives of the pentahydride of phosphorus, in which the five ligands are covalently bonded to phosphorus. The stereochemistry of pentavalent phosphorus relates to the trigonal bipyramid, just as that of tetravalent carbon relates to the tetrahedron. X-Ray crystallographic analysis provides details of the static molecular structure of cyclic oxyphosphoranes. Group theory and topology provide a formal analysis of the way in which trigonal bipyramidal pentacoordinated phosphorus can undergo permutational isomerizations. Theoretical calculations of the energies associated with model situations in the positional exchange of ligands in phosphorus pentafluoride support two mechanisms for this exchange: Berry pseudorotation (BPR) and Turnstile rotation (TR). Cyclic pentacoordinated phosphorus compounds with trigonal bipyramidal symmetry cannot undergo positional exchange of ligands unless a TR mechanism is involved. The TR process may involve single or multiple TR, or TR with “switches.” The TR mechanism could also explain the positional exchange of ligands in other pentacoordinated, trigonal bipyramidal molecules where the central atom is an element other than phosphorus. Regular processes are not the only way by which trigonal bipyramidal phosphorus can undergo permutational isomerization. Irregular processes, involving bond ruptures and reformations, must always be considered as alternatives and some experimental justification or reasoning-by-analogy must be provided in discussions of permutational isomerization itineraries. Irregular permutational isomerizations, which involve a decrease in the pentacoordination of the phosphorus are known, and they are prone to acid catalysis.

5-membered cyclic acyl phosphates : A new class of extremely reactive phosphorylating agents

Abstract The reaction of phosgene with the oxyphosphorane made from biacetyl and trimethyl phosphite gives an α-(dimethylphosphato)-β-ketoacid chloride, which undergoes an intramolecular loss of methyl chloride under catalysis; by CuSO4, and yields the first reported 5-membered cyclic acyl phosphate. The acyl phosphate is attacked exclusively at phosphorus by water, alcohols and phenols, at an extraordinarily rapid rate. In contrast, tertiary amines attack only the Me carbon of the exocyclic OMe group of the acyl phosphate to give quaternary ammonium salts of 5-membered cyclic acyl phosphates. These cyclic mixed anhydrides of phosphoric acid are the most powerful phosphorylating agents for oxygen-containing nucleophiles known at present. The end-products of the phosphorylations are phosphotriesters, phosphodiesters, and phosphomonoesters, containing the easily removable acetoinyl group, [(CH3CO)(CH3)CHO]P(O)(OR)(OR′).

Die 2,2,2-trichlor-t-butyloxycarbonyl-gruppe, eine neue n-schutzgruppe für oligonucleotidsynthesen

Zusammenfassung Es wird der Schutz der heterocyclischen funktionellen Gruppen der Nucleoside mittels der 2,2,2-Trichlor- t -butyloxycarbonyl-Gruppe (TCBOC) beschrieben. Diese N-Schutzgruppe ist gegenuber den in Oligonucleotidsynthesen verwendeten Bedingungen genugend stabil und mit Cobalt(I)-Phthalocyanin bei 0°-20° in neutraler Losung selektiv abspaltbar.

Computerunterstützte mechanistische Analyse der Streith-Reaktion mit dem Programm RAIN

Abstract An improved version of the computer program RAIN (for bilaterally generating Reaction And Intermediate Networks from educts and products; FORTRAN 77, MS-DOS) is presented. Its application is illustrated by the elaboration of a network of mechanistic pathways for the Streith reaction.

Die Synthese eines Cephamderivats mittels Vierkomponenten-Kondensation /The Synthesis of a Cepham Derivative by Four Component Condensation

Abstract A five-step synthesis of a cepham derivative from a known, a,β,β-trihydroxyisobutyraldehyde derivative (1) and the sodium thioenolate of C-formyl N-phthaloyl methyl glycinate (2) is described. The key step of the synthesis is a four component condensation.

N-tert-Butylglyoxylsäureamid als neues Reagens zur Peptid-Segmentverknüpfung via Vierkomponenten-Reaktion (4CR) / N-tert-Butylglyoxylicamide, the New Reagent for Peptide Segment Coupling by Four-Component Reaction

In contrast to the use of other aldehyd components, the Tetra Component Reactions (4CR) of carboxyl acids and primary amines with combinations of N-tert-butylglyoxylicamide and isocyanides produce carbonamides that yield the desired stereochemically uniform condensation products. Often a further advantage of such products is their possibility of being oxidized selectively in the presence of CuCl2 ·2H2O/NEt3/air (containing O2) into the carbonamides of the here used carboxyl acids and primary amines. In particular, such products can thus be converted selectively into α-acylamino and peptide derivatives. In case of the modelpeptide phenylaceticbenzylamide 8a quantitative cleavage yields, in the course of the appropriate dipeptide derivatives (8b-8f) cleavage yields of 56-81% are obtained.

Die 2.2.2-Trichlor -tert-butyloxycarbonyl -Gruppe als N-Schutzgruppe bei Oligonukleotidsynthesen / The 2,2,2-Trichloro-tert-butoxycarbonyl Group, an N-Protecting Group in Oligonucleotide Synthesis

Abstract The preparation and properties of N6 -2,2,2 -trichloro -tert-butoxycarbonyl -adenosine axe described as a model of a new protecting group technique for amino groups in oligo-nucleotide syntheses.

Solid Phase Peptide Synthesis by Four Component Condensation: Peptide Formation on an Isocyano Polymer Support

Abstract Coupling of various protected amino acids or small peptides on an isocyano polymer and in the presence of 1 -methyl-3-formylindole demonstrates the feasibility of peptide formation by four component condensation on a polymer support, and the final peptide is detached from the resin by 50% trifluoroacetic acid in aceto-nitrile at room temperature.