bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemie von α‐Aminonitrilen. 13. Mitteilung. Über die Bildung von 2‐Oxoethyl‐phosphaten (“Glycoladehyd‐phosphaten”) aus rac‐Oxirancarbonitril und anorganischem Phosphat und über (formale) Konstitutionelle Zusammenhänge zwischen 2‐Oxoethyl‐phosphaten und Oligo (hexo‐ und pentopyranosyl)nucleotid‐Rückgraten
Authors: Pitsch Stefan , Pombo‐Villar Esteban , Eschenmoser Albert 
Published: December 2004

Chemistry of α‐Aminonitriles. Formation of 2‐Oxoethyl Phosphates (“Glycolaldehyde Phosphates”) from rac‐Oxiranecarbonitrile and on (Formal) Constitutional Relationships between 2‐Oxoethyl Phosphates and Oligo(hexo‐ and pentopyranosyl)nucleotide BackbonesOxiranecarbonitrile in basic acqueous solution at room temperature reacts regioselectively with inorganic phosphate to give the cyanohydrin of 2‐oxoethyl phosphate (“glycolaldehyde phosphate”), a source of (the hydrate of) the free aldehyde, preferably in the presence of formaldehyde. In aqueous phosphate solution buffered to nearly neutral pH, oxiranecarbonitrile produces the phosphodiester of glycoladehyde as its bis‐cyanohydrin in good yield. In contrast to mono‐ and dialkylation, trialkylation of phosphate with oxiranecarbonitrile is difficult, and the triester derivative is highly sensitive to hydrolysis. Glycolaldehyde phosphate per se is of prebiotic interest, since it had been shown [5] to aldomerize in basic aqueous solution regioselectively to rac‐hexose 2, 4, 6‐triphosphates and – in the presence of formaldehyde ‐ mainly to rac‐pentose 2, 4‐diphosphates with, under appropriate conditions, rac‐pentose 2, 4‐diphosphates as the major reaction product. However, the question as to whether oxiranecarbonitrile itself has the potential of having been a prebiological natural constituent remains unanswered.Backbone structures of hexopyranosyl‐oligonucleotides with phosphodiester linkages specifically between the positions 6′ → 4′, 6′ → 2′, or 4′ → 2′ of the sugar residues can formally be derived via the (hypothetical) aldomerization pathway, a combinatorial intermolecular aldomerization of glycoladehyde phosphate and bis(glycolaldehyde)‐phosphodiester in a 1: 1 ratio. The constitutional relationships revealed by this synthetic analysis has played a decisive role as a selection criterion in the pursuit of our experimental studies toward a chemical etiology of the natural nucleic acids' structure. The Discussion in this paper delineates how the analysis contributed to the conception of the structure of p‐RNA.The English Footnotes to Schemes 1–11 provide an extension of this summary.
Asymmetric Alkylations of a Sultam‐Derived Glycine Equivalent: Practical preparation of enantiomerically pure α‐amino acids
Authors: Oppolzer Wolfgang , Moretti Robert , Zhou Changyou 
Published: December 2004

AbstractAlkylation of the chiral glycine derivative 2 with “activated” organohalides under ultrasound‐assisted phasetransfer catalysis or with activated and nonactivated organohalides in anhydrous medium provides (mostly crystalline) alkylation products 3. Acidic hydrolysis of the pure products 3 gives (aminoacyl)sultams 4 which by mild saponification furnish pure α‐amino acids 5 in good overall yields from 2, along with recovered auxiliary 1 (Scheme 1). Pure ω‐protected α,ω‐diamino acids and α‐amino‐ω‐(hydroxyamino)acids 12–16 are readily accessible from (ω‐haloacyl)sultams 3 via reaction with N‐nucleophiles followed by acidic and basic hydrolyses (Scheme 2). A reliable determination of the enantiomeric purity of α‐amino acids using HPLC analysis of their N‐(3,5‐dinitrobenzoyl)prolyl derivatives 17 is presented.
The Enantioselective Synthesis of the ‘Southern Part’ of Soraphen A
Authors: Loubinoux Bernard , Sinnes Jean‐Luc , O'Sullivan Anthony C. , Winkler Tammo 
Published: December 2004

AbstractUsing a series of enantioselective aldol condensations followed by an ester enolate addition, the cyclic hemiacetal 2 was prepared stereospecifically. Hemiacetal 2 represents the synthetically most challenging ‘southern part’ of the antifungal macrolide soraphen A (1). Spontaneous enolisation of 26, the C(2) epimer of 2, revealed that 2 is the most stable diastereoisomer at room temperature.
Oligosaccharide Analogues of Polysaccharides. Part 2. Regioselective deprotection of monosaccharide‐derived monomers and dimers
Authors: Alzeer Jawad , Vasella Andrea 
Published: December 2004

AbstractThe Me3SiC(1) bond of the bis‐(trimethylsilyl)ethynylated anhydroalditol 2 is selectively cleaved with BuLi to yield 3/4, while AgNO2/KCN in MeOH cleaves the Me3SiC(2′) bond, leading to 5 (Scheme 1). Both Me3Si groups are removed with NaOH in MeOH (→ 7), the (i‐Pr)3Si group is selectively cleaved with HCl in aq. MeOH ( →6); all silyl substituents are removed with Bu4NF ( →8). Acetolysis transformed 9 into 13, which was desilylated to 14, while thiolysis of 9 led to a mixture 11/12. The tetraacetate 14 has also been obtained from 9 via 10. Oxidative dimerisation of either 3 or 5, or of a mixture 3/5 yields only the homodimers 15 and 16 (Scheme 2); treatment of 16 with AgNO2/KCN yielded 17, deprotection proceeding much more slowly than the cleavage of the Me3SiC(2′) group of 2. The iodoalkyne 20, required for the cross‐coupling with 5 according to Cadiot‐Chodkiewicz, was prepared by deprotection of 3/4 to 18, methoxymethylation (→19), and iodination. Cross‐coupling yielded mostly 21, besides the homodimer 22. Similarly, cross‐coupling of 20 and 23 (obtained from 5) led to 24 and 22. The structure of 24 was established by X‐ray analysis (Fig.), showing a C(6)–C(5′) distance of 5.2 Å. The conditions for deprotecting 2 were applied to 21, and led to 25 (AgNO2/KCN), 26 (aq. NaOH), 27 (Bu4NF), and 29 (HCl/MeOH; Scheme 3). Attempted deprotection of the propargylic‐ether moiety with BuLi, however, failed. The dimer 27 was further deprotected to 28. Acetolytic (Ac2O/Me3SiOTf) debenzylation of the dimer 30, obtained from 10, gave 31 (83%) which was deacetylated to 32 (Scheme 4). Cross‐coupling of 5 and the bromoalkyne 33, obtained from 10, yielded 34; again, acetolysis proceeded well, leading to 35. The cellobiose derivative 38 was prepared from the lactone 36 via 37. The glycosidic linkage of 38 proved resistant to the conditions of acetolysis, leading to 39. Acetolysis of the benzylated thiophene 40 (from 30 with Na2S) yielded the octaacetate 41, but proceeded in substantially lower yields (50%).
Oligosaccharide Analogues of Polysaccharides. Part 1. Concept and synthesis of monosaccharide‐derived monomers
Authors: Alzeer Jawad , Cai Chengzhi , Vasella Andrea 
Published: December 2004

AbstractIt is proposed to study the influence of interresidue H‐bonds on the structure and properties of polysaccharides by comparing them to a series of systematically modified oligosaccharide analogues where some or all of the glycosidic O‐atoms are replaced by buta‐1,3‐diyne‐1,4‐diyl groups. This group is long enough to interrupt the interresidue H‐bonds, is chemically versatile, and allows a binomial synthesis. Several approaches to the simplest monomeric unit required to make analogues of cellulose are described. In the first approach, allyl α‐D‐galactopyranoside (1) was transformed via 2 and the tribenzyl ether 3 into the triflate 4 (Scheme 2). Substitution by cyanide (→ 5–7) followed by reduction with DIBAH led in high yield to the aldehyde 9, which was transformed into the dibromoalkene 10 and the alkyne 11 following the Corey‐Fuchs procedure (Scheme 3). The alkyne was deprotected via 12 or directly to the hemiacetal 13. Oxidation to the lactone 14, followed by addition of lithium (trimethylsilyl)acetylide Me3SiCCLi/CeCl3 (→ 15) and reductive dehydroxylation afforded the disilylated dialkyne 16. The large excess of Pd catalyst required for the transformation 11 → 13 was avoided by deallylating the dibromoalkene 10 (→ 17 → 18), followed by oxidation to the lactone 19, addition of Me3SiCCLi to the anomeric hemiketals 20 (α‐D/β‐D 7:2), dehydroxylation to 21, and elimination to the monosilylated dialkyne 22 (Scheme 3). In an alternative approach, treatment of the epoxide 24 (from 23) with Me3SiCCLi/Et2AlCl according to a known procedure gave not only the alkyne 27 but also 25, resulting from participation of the MeOCH2O group (Scheme 4). Using Me3Al instead of Et2AlCl increased the yield and selectivity. Deprotection of 27 (→ 28), dibenzylation (→ 29), and acetolysis led to the diacetate 30 which was partially deacetylated (→ 31) and oxidized to the lactone 32. Addition of Me3SiCCLi/TiCl4 afforded the anomeric hemiketals 33 (α‐D/β‐D 3:2) which were deoxygenated to the dialkyne 34. This synthesis of target monomers was shortened by treating the hydroxy acetal 36 (from 27) with (Me3SiCC)3Al (Scheme 5): formation of the alkyne 37 (70%) by fully retentive alkynylating acetal cleavage is rationalised by postulating a participation of HOC(3). The sequence was further improved by substituting the MeOCH2O by the (i‐Pr)3SiO group (Scheme 6); the epoxide 38 (from 23); yielded 85% of the alkyne 39 which was transformed, on the one hand, via 40 into the dibenzyl ether 29, and, on the other hand, after C‐desilylation (→ 41) into the dialkyne 42. Finally, combined alkynylating opening of the oxirane and the 1,3‐dioxolane rings of 38 with excess Et2Al CCSiMe3 led directly to the monomer 43 which is thus available in two steps and 77% yield from 23 (Scheme 6).
Oligosaccharide Analogues of Polysaccharides. Part 3. A new protecting group for alkynes: Orthogonally protected dialkynes
Authors: Cai Chengzhi , Vasella Andrea 
Published: December 2004

AbstractDialkynes of the type 3 (Scheme 1) are regioselectively deprotected by treating them either with base in a protic solvent (→4), or– after exposing the OH group– by catalytic amounts of base in an aprotic solvent (→5 and 8). The Me3Si‐protected 12 (Scheme 2) is inert to catalytic BuLi/THF which transformed 11 into 9, while K2CO3/MeOH transformed both 10 into 9, and 12 into 13, evidencing the requirement for a more hindered (hydroxypropyl)silyl substituent. C‐Silylation of the carbanions derived from 17–19 (Scheme 3) with 15 led to 20–22, but only 22 was obtained in reasonable yields. The key intermediate 27 was, therefore, prepared by a retro‐Brook rearrangement of 23, made by silylating the hydroxysulfide 16 with 15. The OH group of 27 was protected to yield the {[dimethyl(oxy)propyl]dimethylsilyl}acetylenes (DOPSA's) 21, 28, and 29. The orthogonally protected acetylenes 20–22, 28, and 29 were de‐trimethylsilylated to the new monoprotected acetylene synthons 30–34. The scope of the orthogonal protection was checked by regioselective deprotection of the dialkynes 39–42 (Scheme 4), prepared by alkylation of 35 (→39), or by Pd0/CuI‐catalyzed cross‐coupling with 36–38 (→40–42). The cross‐coupling depended upon the solvent and proceeded best in N,N,N′,N′ ‐teramethylethylenediamine (TMEDA). Main by‐product was the dimer 43. On the one hand, K2CO3/MeOH removed the Me3Si group and transformed 39–42 into the monoprotected 44–47; catalytic BuLi/THF, on the other hand, transformed the alcohols 48–51, obtained by hydrolysis of 39–42, into the monoprotected dialkynes 52–55, all steps proceeding in high yields. Addition of the protected DOPSA groups to the lactones 56 (→57–59) and 62 (→63) (Schemes 5 and 6) gave the corresponding hemiketals. Reductive dehydroxylation of 57 and 58 failed; but similar treatment of 59 yielded the alcohol 61. Similarly, 63 was transformed into 64 which was protected as the tetrahydropyranyl (Thp) ether 65. In an optimized procedure, 62 was treated sequentially with lithiated 31, BuLi, and Me3SiCl (→66), followed by desilyloxylation to yield 60% of 67, which was protected as the Thp ether 68. Under basic, protic conditions, 68 yielded the monoprotected bisacetylene 69; under basic, aprotic conditions, 67 led to the monoprotected bisacetylene 70. These procedures are compatible with the butadiynediyl function. The butadiyne 73 was prepared by cross‐coupling the alkyne 69 and the iodoalkyne 71 (obtained from 70, together with the triiodide 72) and either transformed to the monosilylated 76 or, via 77, to the monosilylated 78. Formation of the homodimers 74 and 75 was greatly reduced by optimizing the conditions of cross–coupling of alkynes.
Macrocyclic Tetraethynylethene Molecular Scaffolding: Perethynylated aromatic dodecadehydro[18]annulenes, antiaromatic octadehydro[12]annulenes, and expanded radialenes
Authors: Anthony John , Boldi Armen M. , Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice , Seiler Paul , Knobler Carolyn B. , Diederich François 
Published: December 2004

AbstractTetraethynylethene (3,4‐diethynylhex‐3‐ene‐1,5‐diyne) molecular scaffolding provided access to novel macrocyclic nanometer‐sized C‐rich molecules with unusual structural and electronic properties. Starting from cis‐bis‐deprotected cis‐bis(trialkylsilyl)protected tetraethynylethenes, the per(silylethynyl)ated octadehydro[12]annulenes 1 and 2 and the corresponding dodecadehydro[18]annulenes 4 and 5 were prepared by oxidative Hay coupling. X‐Ray crystal‐structure analyses of (i‐Pr)3Si‐protected 2 and Me3Si‐protected 4 showed that both annulene perimeters are perfectly planar. Electronic absorption spectral comparisons provided strong evidence that the macro rings in the deep‐purple‐colored 1 and 2 are antiaromatic (4n π‐electrons), whereas those in yellow 4 and 5 are aromatic ((4n + 2) π‐electrons). Although unstable in solution, the antiaromatic compound 2 gave high‐melting crystals in which the individual octadehydro[12]annulene chromophores are isolated and stabilized in a matrix‐type environment formed by the bulky (i‐Pr)3Si groups. Electrochemical studies demonstrated that the antiaromatic octadehydro[12]annulene 2 undergoes two stepwise one‐electron reductions more readily that the aromatic chromophore 5. This redox behavior is best explained by the formation of an aromatic (4n + 2) π‐electron dianion from 2, whereas 5 loses its aromaticity upon reduction. The Me3Si derivative 4 was deprotected with borax in MeOH/THF to give the highly unstable hexaethynyl‐dodecadehydro[18]annulene 6, a C30H6 isomer and macrocyclic precursor to a two‐dimensional all‐C‐network. Deprotection of 2 did not give isolable amounts of tetraethynyl‐octadehydro[12]annulene 3 due to the extreme instability of the latter. Starting from dimeric and trimeric acyclic tetraethynylethene oligomers, a series of expanded radialenes were obtained. They possess large C‐cores with silylethynyl‐protected peripheral valences and can be viewed as persilylated C40 (7), C50 (8), and C60 (9) isomers. These expanded C‐sheets are high‐melting, highly stable, soluble materials which were readily characterized by laser‐desorption time‐of‐flight (LD‐TOF) mass spectrometry. Due to inefficient macrocyclic cross‐conjugation and/or non‐planarity, the extent of π‐electron delocalization in 7–9 is limited to the longest linearly conjugated π‐electron fragment. In agreement with these properties, all three expanded radialenes exhibited similar redox behavior; they are difficult to oxidize but undergo several reversible one‐electron reductions in similar potential ranges. Presumably, the reduced π‐electron delocalization is also at the origin of the particularly high stability of 7–9.
Über die Biosynthese von γ‐Dodecanolacton in reifenden Früchten: Aroma‐Komponenten der Erdbeere (Fragaria ananassa) und des Pfirsichs (Prunus persica)
Authors: Schöttler Michael , Boland Wilhelm 
Published: December 2004

On the Biosynthesis of γ‐Dodecanolactone in Ripening Fruits: Flavor Constituents from Strawberries (Fragaria ananassa) and Peaches (Prunus persica)Administration of deuterium‐labelled 9,10‐expoxy[8,8‐2H2]heptadecanoic acid 8a/b and 9,10‐dihydroxy‐[8,8‐2H2]methylheptadecanoate 9 as lower analogues of oleic acid 1 to ripening fruits of strawberries (Fragaria ananassa) and peaches (Prunus persica) results in the emission of labelled γ‐undecanolactone (5) as the lower analog of γ‐dodecanolactone (2). The transformation proceeds with loss of a single D‐atom from C(8) of the precursors. Early precursors, like the C17‐epoxy‐acids 8a/b yield (4R)‐γ‐undecanolactone (5) of high enantiomeric purity, while later intermediates results in (4R)‐γ‐undecanolactone (5) of low purity. The data support a biosynthetic sequence involving the consecutive action of an epoxide hydrolase and β‐oxidation to generate the correct chain length of the lactone percursor. The final steps proceed via cyclization of the 3,4‐dihydroxyundecanoic acid 13 to the 3‐hydroxy‐γ‐undecanolactone 14. Elimination of H2O and reduction of the intermediate γ‐undec‐2‐enolactone 15 terminate the biosynthesis of 5. The sequence is representative for the biosynthesis of naturally occurring γ‐dodecanolactone (2).
Optisch aktive 3‐Amino‐2H‐azirine als Bausteine für enantiomerenreine α,α‐disubstituierte α‐Aminosäuren: Synthese des α‐Methylphenylalanin‐Synthons and Einbau in Modell‐Peptide
Authors: Bucher Christoph B. , Linden Anthony , Heimgartner Heinz 
Published: December 2004

Optically Active 3‐Amino‐2H‐azirines as Synthons for Enantiomerically Pure αα‐Disubstituted α‐Amino Acids: Synthesis of the α‐Methylphenylalanine Synthons and Some Model PeptidesThe synthesis of a novel 2‐benzyl‐2‐methyl‐3‐amino‐2H‐azirine derivative with a chiral amino group is described. Chromatographic separation of the diastereoisomer mixture yielded the pure diastereoisomers 9a and 9b (Scheme 4) which are the D‐ and L‐2‐methylphenylalanine ((α‐Me)Phe) synthons, respectively. The reaction of 9a and 9b with thiobenzoic acid and with Z‐leucine yielded the monothiodiamides 10a and 10b (Scheme 5) and the dipeptide derivatives 11a and 11b (Scheme 6), respectively. Methanolysis of 11b yielded 12b. The absolute configuration of 10a was established by X‐ray crystallography. The absolute configuration of (α‐Me)Phe in 12b has been deduced from the known configuration of L‐leucine.
Enantioselektive Synthese von Allyl‐, Propargyl‐ und 4‐En‐2‐inyl‐aminen durch 1,2‐Addition von Organocer‐Reagenzien an chirale Aldimine
Authors: Enders Dieter , Schankat Jürgen 
Published: December 2004

Enantioselective Synthesis of Allyl‐, Propargyl‐, and 4‐En‐2‐ynyl‐amines via 1,2‐Addition of Organocerium Reagents to Chiral Aldehyde Imines(E)‐ and (Z)‐Allyl‐, propargyl‐, and 4‐en‐2‐ynyl‐amines 5 and 14, useful bifunctional building blocks and of pharmaceutical interest, are synthesized in high enantiomeric purity (e.e. ≥ 97%). Key step is the diastereoselective 1,2‐addition (d.e. 86 to ≥ 98%) of organocerium reagents to chiral α,β‐unsaturated aldehyde imines 3 or 8 to produce adduct amines 4 and 9 (Schemes 1 and 4, resp.). The propargylamine 9 is a substrate for Pd‐catalyzed coupling with alkenyl halides to produce the enynylamine 11a and the thienyl‐substituted alkynylamine 11b. The chiral auxiliary (S,S)‐2 is removed from 4 and 11 in 3 steps affording the title compounds 5 and 14. Diastereoisomer enrichment of the hydrochloride of 6 by crystallization is possible.
Bildung von 1,2,4‐Trithiolanen in Dreikomponenten‐Gemischen aus Phenyl‐azid, aromatischen Thioketonen und 2,2,4,4‐Tetramethylcyclobutanthionen: Eine Schwefel‐Transfer‐Reaktion unter Bildung von ‘Thiocarbonylthiolaten’ ((Alkylidensulfonio)thiolaten) als reaktive Zwischenstufen
Authors: Mlostoń Grzegorz , Heimgartner Heinz 
Published: December 2004

Formation of 1,2,4‐Trithiolanes in Three‐Component Reactions of Phenyl Azide, Aromatic Thiones, and 2,2,4,4‐Tetramethylcyclobutanethiones: A Sulfur‐Transfer Reaction to ‘Thiocarbonyl‐thiolates’ ((Alkylidenesulfonio)‐thiolates) as Reactive IntermediatesThe reaction of PhN3 and aromatic thioketones 18 (two‐component reaction) at 80° yields only the corresponding imines 22, S, and N2. Under similar conditions, in the presence of sterically crowded 2,2,4,4‐tetramethyl‐cyclobutanethiones 19 (three‐component reaction), 1,2,4‐trithiolanes of type 20 are formed in good yields in addition to imines 22 (Scheme 4). In case of 19a and 19c (X = CO, CS), the symmetrical trithiolanes 21a and 21b, respectively, are also isolated. With 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5(4H)‐thione (24) instead of aromatic thioketone 18, imine 25, trithiolane 21a, and 1,4,2‐dithiazolidine 26 are formed (Scheme 5). A reaction mechanism for the formation of 1,2,4‐trithiolanes 20 and 21, including an S‐transfer to generate ‘thiocarbonyl‐thiolates’ 2b and/or 2c and 1,3‐dipolar cycloaddition with a thioketone, is proposed in Scheme 7.
Novel open‐chain and cyclic conformationally constrained (R)‐ and (S)‐α,α‐disubstituted tyrosine analogues
Authors: Obrecht Daniel , Lehmann Christian , Ruffieux Ruth , Schönholzer Peter , Müller Klaus 
Published: December 2004

AbstractA series of novel open‐chain and cyclic conformationally constrained (R)‐ and (S)‐α,α‐disubstituted tyrosine analogues 1a–e were synthesized in good yields and high optical purities (Schemes 1 and 2). The absolute configurations of these tyrosine analogues were unambiguously determined based on the X‐ray structures of the precursor diastereoisomeric peptides of type 4 and 5. Four of these structures are described (Figs. 1–4), showing β‐turn type‐I geometries for dipeptides 4a, 5b, and 4c and an extended conformation for peptide 5c (Table 3). The conversion of the free amino acids 1a–c into suitably protected building blocks 11a–d and 15d,e for peptide synthesis is discussed (Schemes 3 and 4).
Synthesis and Reductive Complexation Properties of a Cone‐Configurated Tetra[p‐(tert‐butyl)]calix[4]arene incorporating bipyridyl and pyridine subunits. NMR characterization and crystal structure of its chiral copper(I) complex
Authors: Regnouf De Vains Jean‐Bernard , Lamartine Roger , Fenet Bernard , Bavoux Claude , Thozet Alain , Perrin Monique 
Published: December 2004

AbstractThe hetero‐armed p(tert‐butyl)calix[4]arene 1 was synthesized by a stepwise procedure. This ligand presented a very strong complexing behavior towards Cu1, giving the chiral complex 2 and parent species when reacted with CuII salts. High‐resolution NMR techniques were employed for the characterization of 2, demonstrating notably exchange processes between its two enantiomeric forms. The racemic nature of 2 was confirmed by X‐ray crystal‐structure analysis.
Bortrifluorid‐katalysierte Umsetzungen von 3‐Amino‐2H‐azirinen mit Aminosäure‐estern und Aminen
Authors: Hugener Martin , Heimgartner Heinz 
Published: December 2004

Boron‐Trifluoride‐Catalyzed Reactions of 3‐Amino‐2H‐azirines with Amino‐acid Esters and AminesAfter activation by protonation or complexation with BF3, 3‐amino‐2H‐azirines 1 react with the amino group of α‐amino‐acid esters 3 to give 3,6‐dihydro‐5‐aminopyrazin‐2(1H)‐ones 4 by ring enlargement (Scheme 2, Table 1). The configuration of 3 is retained in the products 4. With unsymmetrically substituted 1 (R1 ≠ R2), two diastereoisomers of 4 (cis and trans) are formed in a ratio of 1:1 to 2:1. With β‐amino‐acid esters 5 and 7, only openchain α‐amino‐imidamides 6 and 8, respectively, are formed, but none of the seven‐membered heterocycle (Scheme 3). Primary amines also react with BF3‐complexed 1 to yield α‐amino‐imidamides of type 9 (Scheme 4, Table 2). Compound 9b is characterized chemically by its transformation into crystalline derivatives 10 and 12 with 4‐nitrobenzoyl chloride and phenyl isothiocyanate, respectively (Scheme 5). The structure of 12 is established by X‐ray crystallography. Mechanisms for the reaction of activated 1 with amino groups are proposed in Schemes 6 and 7.