Synthese und Chiralität der stereoisomeren Achillene,Achillenole und Hymentherene

(+)-cis-Achillene ( 10 ) and (?)-trans-achillenol (7), two monoterpenes recently isolated [1] from the essential oil of Achilleafilipendulina, were synthesized, together with their stereoisomers (?)-(9) and (+)-(8), starting from (S)-(+)-2,6-trans-dimethylocta-1,3, 7-triene ( 1 ). The isomeric ß-hymen thereties ((?)- 3 and (+)-4), often quoted [2] [3] [4] but never isolated, were obtained as intermediates. The mode of synthesis chosen establishesis (R)-chirality for naturally occurring (?)-trans-achillenol (7) and (+)-cis-achillene ( 10 ) as well as for the purely synthetic 4, 7-diene derivatives described in this paper.     

Synthese von 1-Ary1-4-methylthio-2-azetidinonen

TheN-arylthioformimidates4 a-e, which may be obtained byS-alkylation of the thioformanilides3 a-e, react with chloroacetylchloride/triethylamine to yield the (3R,4S/3S,4R)-1-aryl-3-chloro-4-methylthio-2-azetidinones5 a-e and the formanilides6 a-e. Dehalogenation of5 b-e with tri-n-butyltinhydride yield the title compounds7 b-e. Hydrogenolysis of7 b and7 c yields7 f and7 g.

     

Stereochemical Analysis of an Aromatic Triplet Di-π-methane Rearrangement

It is shown that (−)-(S)-N,N-dimethyl-2-(1′-methylallyl)aniline ((−)-(S)- 4 ), on direct irradiation in MeCN at 20°, undergoes in its lowest-lying triplet state an aromatic di-π-methane (ADPM) rearrangement to yield (−)-(1′R,2′R)- and (+)-(1′R,2′S)-N,N-dimethyl-2-(2-methylcyclopropyl)aniline ((−)-trans- and (+)-cis- 7 ) in an initial trans/cis ratio of 4.71 ± 0.14 and in optical yields of 28.8 ± 5.2% and 15 ± 5%, respectively. The ADPM rearrangement of (−)-(S)- 4 to the trans- and cis-configurated products occurs with a preponderance of the path leading to retention of configuration at the pivot atom (C(1′) in the reactant and C(2′) in the products) for (−)-trans- 7 and to inversion of configuration for (+)-cis- 7 , respectively. The results can be rationalized by assuming reaction paths which involve the occurrence of discrete 1,4- and 1,3-diradicals (cf. Schemes 10, 12, and 13). A general analysis of such ADPM rearrangements which allows the classification of these photochemical reactions in terms of borderline cases is presented (Scheme 14). It is found that the optical yields in these ‘step-by-step’ rearrangements are determined by the first step, i.e. by the disrotatory bond formation between C(2) of the aromatic moiety and C(2′) of the allylic side chain leading to the generation of the 1,4-diradicals. Moderation of the optical yields can occur in the ring closure of the 1,3-diradicals to the final products, which may take place with different trans/cis-ratios for the individual 1,3-diradicals. Compounds (−)-trans- 7 as well as (+)-cis- 7 easily undergo the well-known photochemical trans/cis-isomerization. It mainly leads to racemization. However, a small part of the molecules shows trans/cis-isomerization with inversion of configuration at C(1′), which is best explained by a photochemical cleavage of the C(1′)–C(3′) bond.     

Zur Synthese von Imidazo(2,1-b)-1,3,4-thiadiazolo(3,2-a)-pyrimidonen-(6)

2-Amino-6-aryl-imidazo(2,1-b)-1,3,4-thiadiazoles (1 a-f) were condensed with 1,3-ketocarboxylates e. g. ethyl-butyroacetate, ethyl-benzoylacetate, 4-nitrobenzoylacetate or ethyl-cyclopentanone(2)-carboxylate and ethyl-cyclohexanone(2)-carboxylate directly to imidazo(2,1-b)-1,3,4-thiadiazolo(3,2-a) pyrimidones-(6) (4 a-f, 5 a-f, 6 d, e, 7 a-f, 8 a, d).

11. Mitt. über Heterocyclen; 10. Mitt.Paul, H., Sitte, A., Wessel, R., Arch. Pharm. (Weinheim), im Druck.     

synthesis of sempervirine,a pentacyclic anhydronium indole alkaloid

Summary Sempervirine (2,3,4,13-tetrahydro-1H-benz[g]indolo[2,3-a]quinolizin-6-ium,1) the pentacyclic anhydronium indole alkaloid ofGelsemium sempervirens Ait. f. (Loganiaceae), has been synthesized in three steps from hexahydroisochroman-3-one (6) and N-2-(3-indolyl)-ethylamine (tryptamine,7). The condensation product, N-2-(3-indolyl)-ethyl-2-(hydroxymethyl)-trans-hexahydrophenylacetamide (8) arising from6 and7 on double cyclization with phosphoryl chloride yielded the 3,4-dehydroyohimbane derivative9. Aromatization of rings C and D of compound9 with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in glacial acetic acid, followed by basification, generated sempervirine (1).

---

Synthese von Sempervirin, einem pentacyclischen Anhydronium-Indolalkaloid

Zusammenfassung Sempervirin (2,3,4,13-Tetrahydro-1H-benz[g]indolo[2,3-a]chinolizin-6-ium,1), das pentacyclische Anhydronium-Indolalkaloid vonGelsemium sempervirens Ait f. (Loganiceae) wurde ausgehend von Hexahydroisochroman-3-on (6) und N-2-(3-Indolyl)-ethylamin (Tryptamin,7) in 3 Stufen synthetisiert. Das durch doppelte Cyclisierung von6 und7 mit Phosphorylchlorid entstehende Kondensationsprodukt N-2-(3-Indolyl)-ethyl-2-(hydroxymethyl)-trans-hexahydrophenylacetamid (8) ergab das 3,4-Dehydroyohimbanderivat9. Aromatisierung der Ringe C und D von9 mit 2,3-Dichlor-5,6-dicyanobenzochinon (DDQ) in Eisessig und anschließende Einstellung eines basischenpH-Werts lieferte Sempervirin (1).

     

Natural product synthesis from (8aR)- and (8aS)-bicyclofarnesols: synthesis of (+)-wiedendiol A, (+)-norsesterterpene diene ester and (−)-subersic acid

Both enantiomers (8aR)-7 and (8aS)-7 of bicyclofarnesol were synthesized from the enzymatic resolution products (1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-5 (98% ee) and acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aS)-6 (>99% ee), respectively. The formal synthesis of (+)-wiedendiol 1 was achieved via a coupling reaction of an ate complex derived from 1,2,4-trimethoxybenzene with allyl bromide (8aS)-8 derived from (8aS)-7. The total synthesis of (+)-norsesterterpene diene ester 2 was achieved, based on the synthesis of (13E,10S)-α,β-unsaturated aldehyde 12, derived from (8aS)-7, followed by the selective construction of the (3E,5E)-diene moiety including a C(2)-stereogenic centre in (+)-2. The total synthesis of (−)-subersic acid 3 was carried out based on a Stille coupling between allyl trifluoroacetate congener 25c, derived from (8aR)-7, corresponding to the diterpene part, and aryl stannane congener 26 in the presence of Pd catalyst and CuI as an additive.     

Hetero-Diels-Alder reaction of some 1,3-diaza-1,3-butadienes with ketenes. Synthesis of functionalized pyrimido[1,2-b]-benzothiazoles and 1,3,4-thiadiazolo-[3,2-a]pyrimidines

Summary Reaction of 1,3-diaza-1,3-butadienes (1a–c) with various ketenes and chloroketenes results in the formation of substituted 4-oxo-pyrimido[2,1-b]benzothiazoles (4a–d) and 1,3,4-thiadiazolo[3,2-a]pyrimido-4-ones (4e,f). Reaction of 1,3-diaza-1,3-butadienes1d,e with ketenes and chloroketenes leads to the 2-morpholine-substituted compounds7 and15, respectively. All reactions proceedvia formation of [4+2] cycloadducts that eliminate methylthiol, methylsulfenyl chloride, or morpholine.

---

Hetero-Diels-Alder-Reaktion einiger 1,3-Diaza-1,3-butadiene mit Ketenen. Synthese funktionalisierter Pyrimido[1,2-b]benzothiazole und 1,3,4-Thiadiazolo[3,2-a]pyrimidine

Zusammenfassung Die Reaktion der 1,3-Diaza-1,3-butadiene1a–c mit verschiedenen Ketenen und Chlorketenen führt zu substituierten 4-Oxo-pyrimido[2,1-b]benzothiazolen (4a–d) und 1,3,4-Thiadiazolo[3,2-a]pyrimido-4-onen(4e,f). Die 1,3-Diaza-1,3-butadiene1d,e ergeben mit Ketenen und Chlorketenen die 2-Morpholin-substituierten Verbindungen7 und15. Alle Reaktionen verlaufen über [4+2]-Cycloaddukte, die Methylthiol, Methylsulfenylchlorid oder Morpholin eliminieren.

     

Darstellung,absolute Konfiguration und optische Reinheit von 2,2′-Spiro-biindan-1,1′-dion

The absolute configuration of 2.2-spirobiindane-1.1-dione (2) was established as (+)-(2S) by correlation with a centrochiral key intermediate, namely by cyclization of (+)-(2R)-2-benzyl-2-methoxycarbonyl-1-indanone (9) withPPA.9 was obtained by oxidation of either methyl (+)-cis- ortrans-1-hydroxy-2-benzyl-indane-2-carboxylate (8 a, 8 b), whose absolute configurations were determined as (+)-(1S, 2R) and (1R, 2R), resp., byHoreau's method and whose optical purities by the NMR-method employing the esters with -methoxy--trifluoromethylphenyl-acetic acid. The active methyl esters8 were prepared starting from the corresponding racemic ethyl ketocarboxylate4, which on reduction afforded the stereoisomeric ethylcis- andtrans-1-hydroxyindane-2-benzyl-2-carboxylates (5 a, 5 b); their relative configurations were determined by NMR. The corresponding acids7 were resolvedvia the cinchonidine salts and obtained in high optical purity (100% fortrans, 80% forcis).Levorotatory2 was also prepared by resolution of the bis-aminoxyacetic acid derivative (via its bis-cinchonidine salt) and subsequent cleavage. [a] _D ^max of2 was determined as ±240° (benzene) by means of a chiral shift reagent. The racemization of2 withPPA under the conditions of the asymmetric synthesis was studied.

---

---

Mit 4 Abbildungen     

Synthesis, resolution and assignment of absolute configuration of trans 3-amino-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (POAC), a cyclic, spin-labelled β-amino acid

Racemic trans 3-(9-fluorenylmethyloxycarbonylamino)-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (Fmoc-POAC-OH), prepared by conventional methods, was resolved upon esterification with (aR)-2,2′-dihydroxy-1,1′-binaphthyl. Separation of the obtained diastereomeric monoesters Fmoc-(±)-trans-POAC-O-(aR)-binaphthol by crystallization/chromatography, and removal of the chiral auxiliary by saponification of the aryl ester function furnished both enantiomers (+)-(3R,4R)-Fmoc-POAC-OH and (−)-(3S,4S)-Fmoc-POAC-OH. The absolute configuration of the asymmetric C³, C⁴ carbons of POAC were assigned from the induced circular dichroism of a flexible biphenyl probe present in the terminally protected dipeptide derivatives Boc-Bip-(+)-POAC-OMe and Boc-Bip-(−)-POAC-OMe (Bip, 2′,1′:1,2;1″,2″:3,4-dibenzcyclohepta-1,3-diene-6-amino-6-carboxylic acid). This assignment was confirmed by X-ray diffraction analysis of the diastereomeric monoester Fmoc-(+)-trans-POAC-O-(aR)-binaphthol, shown to be (aR,3R,4R). Solution synthesis of peptides to the hexamer level, based on the (3R,4R)-POAC enantiomer combined with (1S,2S)-2-aminocyclopentane-1-carboxylic acid, was carried out to examine coupling conditions at both C- and N-termini of the POAC residue, in view of further syntheses and 3D-structural investigations.     

Synthesis of (+)-1,3:2,5-dianhydroviburnitol ((+)-(1R,2R,3S,5R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol)

Epoxidation of (?)-(1R,2R,4R)-2-endo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((?)-5) followed by saponification afforded (+)-(1R,4R,5R,6R)-5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7). Reduction of (+)-7 with diisobutylaluminium hydride (DIBAH) gave (+)-1,3:2,5-dianhydroviburnitol ( = (+)-(1R,2R,3S,4R,6S)-4,7-dioxatricyclo[3.2.1.0^3,6]octan-2-ol; (+)-3). Hydride reductions of (±)-7 were less exo-face selective than reductions of bicyclo[2.2.1]heptan-2-one and its derivatives with NaBH₄, AlH₃, and LiAlH₄ probably because of smaller steric hindrance to endo-face hydride attack when C(5) and C(6) of the bicyclo-[2.2.1]heptan-2-one are part of an exo oxirane ring.     

Enantiomerically pure 7-oxabicylo[2.2.1]hept-5-en-zyl derivatives as synthetic intermediates. Part III. Total synthesis of D- and L-ribose derivatives

Enantiomerically pure methyl 5-bromo-5-deoxy-2,3-O- isopropylidene-β-D - (D - 5b ) and -β-l-ribofuranoside (l- 5b ) have been derived from (?)-(1R,2S,4R)-2-exo-cyano-7-oxabicylo[2.2.1]hept-5-en-endo,-yl (1′S)-camphanate ( 1 ) and (+)-(1S,2R,4S)-2-exo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl(1′R)-camphanate ( 2 ), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D-5b and L - 5b afforded methyl 2,3-O isopropylidene-β-D -ribofuranoside (D -5a) and methyl 2,3-O-isopropylidene β-L-ribofuranoside (L-5a), respectively. The intermediate (+)-(1R,4R,5R,6R) 5-exo,6-exo-(isopropylidenedioxy)- 7 -oxabicyclo[2.2.1]heptan-2-one ((+)- 7 ) and its enantiomer(–)-7 were also obtained enantiomerically pure by resolution of (=)- 7 by the Johnson-Zeller method. In bothe approaches, the chiral auxiliaries ((–)- and (+)-camphanic acids, or (+)-(S)-N,S-dimethyl-S-phenylsulfoximide) were recovered at an early stage of the synthesis.     

Compounds with bridgehead nitrogen. 42—1H NMR and stereochemistry of isomeric 6a-methylperhydroindolo[3,2,1-i,j]benzoxazines and the position of conformational equilibrium in perhydropyrrolo[1,2-c][1,3]oxazine

The ¹H NMR parameters of the NCH₂O protons in the spectrum of perhydropyrrolo[1,2-c][1,3]oxazine show its existence in solution at room temperature in the O-inside cis-fused conformation. rel-(3aS,6aS,6bR,10aS,11aS)-6a-Methylperhydroindolo[3,2,1-i,j]benzoxazine and rel-(3aS,6aS,6bS,10aR,11aS)-6a-methylperhydroindolo[3,2,1-i,j]benzoxazine are shown to adopt cis- and trans-fused conformations, respectively, for the corresponding bicyclic moiety.     

Circular Dichroism of Tricarbonyl(diene)iron Complexes. The Octant Rule Applied to Ketones Perturbed by Remote Fe(CO)3 Groups. Crystal Structure of (±)-Tricarbonyl[(1RS,4RS,5RS,6SR)-C5,6,C-η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron

The preparation and the CD spectra of optically pure (+)-trans-μ-[(1R,4S,5S,6R,7R,8S)-C,5,6,C -η : C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo [2.2.2]octanone)]bis(tricarbonyliron) ((+)- 7 ) and (+)-tricarbonyl[(1S,4S,5S,6R)-C-5,6,C-η-(5,6,7,8,-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron ((+)- 8 ), and of its 3-deuterated derivatives (+)-trans-μ-[(1R,3R,4S,5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C-η-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]-(octanone)]bis(tricarbonyliron) ((+)- 11 ) and (+)-tricarbonyl[(1S,3R,4S,5S,6R)-C-5,6,C- η-(5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone)]iron ((+)- 12 ) are reported. The chirality in (+)- 7 and (+)- 8 is due to the Fe(CO)₃ moieties uniquely. The signs of the Cotton effects observed for (+)- 7 and (+)- 8 obey the octant rule (ketone n→π*_CO transition). Optically pure (?)-3R-5,6,7,8-tetramethylidene(3-D)-2-bicyclo[2.2.2]octanone ((?)- 10 ) was prepared. Its CD spectrum showed an ‘anti-octant’ behaviour for the ketone n→π*_CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (?)-trans-μ-[(1R,2R,4S, 5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]bis(tricarbonyliron) ((?)- 2 ) and (?)-tricarbonyl- [(1S,2R,4S,5S,6R)- C,5,6,C- η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanol)]iron ((?)- 3 ) and of the 3-denterated derivatives (?)- 5 and (?)- 6 are also reported. The CD spectra of the complexes (?)- 2 , (?)- 3 , (+)- 7 , and (+)- 8 were solvent and temperature dependent. The ‘endo’-configuration of the Fe(CO)₃ moiety in (±)- 8 was established by single-crystal X-ray diffraction.     

Stereochemistry of planarchiral compounds,XIV. Static and dynamic stereochemistry of 3,3′-dimethoxy-2,2′-bi(1,6-methano[10]annulenyl)

Summary The title compound6 was prepared from 3-methoxy-1,6-methano[10]annulene (4)via lithiation and oxidative coupling of the intermediate5 with copper(II)chloride. Three stereoisomers (two rotamers of the racemate,6a and6b, and themeso-form6c) were obtained and their configurations assigned both by¹H NMR spectroscopy and by X-ray crystal structure analysis of6a.Starting the reaction sequence from optically active 2-bromo-1,6-methano[10]annulene, (–)-3, of known absolute chirality (S)_p established the absolute stereochemistry of (+)-6a as (R)_p(R)_a(R)_p and (R)_p(S)_a(R)_p for the dextrorotatory rotamer6b. 3-Methoxy-1,6-methanol[10]annulene (4) as well as6a and6b were easily resolved by enantioselective chromatography of the racemic mixtures on cellulose triacetate (CTA) in ethanol. A rotational barrier of G ^#=132 kJ·mol^–1 between6a and6b was determined both by thermal equilibration and by CD-kinetics.Finally, also themeso-form6c — because of its high rotational barrier (118 kJ) — could be resolved onCTA in its enantiomers ([]_D=200° in ethanol). From chiroptical comparison (CD) with6a and6b, resp., the chirality (R)_p(S)_a(S)_p was deduced for (+)-6c.

---

Stereochemie planarchiraler Verbindungen, 14. Mitt. Statische und dynamische Stereochemie von 3,3-Dimethoxy-2,2-bi(1,6-methano[10]annulenyl)

Zusammenfassung Die Titelverbindung6 wurde aus 3-Methoxy-1,6-methano[10]annulen (4) durch Lithiierung und anschließende oxidative Kupplung des Zwischenproduktes5 mit Kupfer(II)chlorid erhalten. Dabei entstanden3 Stereoisomere (2 Rotamere des Racemates,6a und6b, und diemeso-Form6c), deren Konfiguration sowohl durch¹H-NMR-Spektroskopie als auch durch Röntgenstrukturanalyse von6a bestimmt wurden.Ausgehend von optisch aktivem 2-Brom-1,6-methano[10]annulen, (–)-3, bekannter Absolutkonfiguration (S)_p, konnte durch diese Reaktionsfolge die absolute Chiralität von (+)-6a als (R)_p(R)_a(R)_p [und (R)_p(S)_a(R)_p für (+)-6b] ermittelt werden. Sowohl4 als auch6a und6b waren durch enantioselektive Chromatographie an Cellulose triacetat (CTA) in Ethanol glatt in ihre Enantiomeren trennbar. Die Rotationsbarriere zwischen6a und6b wurde sowohl durch thermische Äquilibrierung als auch CD-Kinetik zu G ^#=132 kJ·mol^–1 bestimmt.Schließlich ließ sich auch die Mesoform6c wegen ihrer hohen Rotationsbarriere von 118 kJ·mol^–1 anCTA glatt in ihre Enantiomeren trennen ([]_D=200° in Ethanol). Aus einem chiroptischen Vergleich mit6a bzw.6b (CD) wurde für (+)-6c die Chiralität (R)_p(S)_a(S)_p abgeleitet.

     

Synthesis of decalin type chiral synthons based on enzymatic functionalisation and their application to the synthesis of (−)-ambrox and (+)-zonarol

Stereoselective syntheses of (−)-ambrox 2 and (+)-zonarol 3 were achieved based on the enzymatic syntheses of (8aS)- and (8aR)-decalin-type 1,3-diols 1, respectively. Non-racemic intermediates such as (8aS)-1 and (8aR)-1 were obtained based on the enantioselective hydrolyses of the phenolic acetal derivative (±)-7 by acylase I.     

Oxazepines and thiazepines,XXIV synthesis of optically active 2,3-dihydro-2-methyl-1,5-benzoxazepin-4(5H)-ones

Summary 2,3-Dihydro-2(R)-methyl-1,5-benzoxazepin-4(5H)-one [(R)-3] and its enantiomer (S)-3 have been synthesized via the optical resolution and subsequent chemical transformations of (±)-3-(2-nitrophenoxy)butyric acid (1). Compounds (R)-3 and (S)-3 were converted into optically active 1,5-benzoxazepines (R)-7–(R)-14 and (S)-15–(S)-32.

---

Oxazepine und Thiazepine, XXIV: Darstellung optisch aktiver 2,3-Dihydro-2-methyl-1,5-benzoxazepin-4(5H)-one

Zusammenfassung 2,3-Dihydro-2(R)-methyl-1,5-benzoxazepin-4(5H)-on [(R)-3] und sein Enantiomeres (S)-3 wurden durch Racemattrennung und weitere chemische Umsetzungen von (±)-3-(2-Nitrophenoxy)buttersäure (1) dargestellt. Die Verbindungen (R)-3 und (S)-3 wurden in die optisch aktiven 1,5-Benzoxazepine (R-7 bis (R)-14 und (S)-15 bis (S)-32 übergeführt.

     

Total syntheses and antimicrobial activities of pyridine alkaloids from Rubiaceae

Summary Pyridine alkaloids from Rubiaceae were prepared by palladium-catalyzed cross-coupling reactions of methyl 5-bromonicotinate (6) with various organometallic reagents. Baker's yeast reduction of the ketone8 gave the levorotatory alcohol (S)-1. On this basis, the naturally occurring alcohol (+)-1 was assigned to be (R)-configurated. The alkaloids1 and4 show weak antimicrobial activities.

---

Totalsynthesen und antimikrobielle Aktivität von Pyridin-Alkaloiden aus Rubiaceen

Zusammenfassung Pyridin-Alkaloide aus Rubiaceen wurden durch palladium-katalysierte Kupplungsreaktionen von 5-Bromnicotinsäuremethylester (6) mit verschiedenen organometallischen Verbindungen hergestellt. Reduktion des Ketons8 mit Bäckerhefe ergab den linksdrehenden sekundären Alkohol (S)-1. Daher weist der natürlich vorkommende Alkohol (+)-1(R)-Konfiguration auf. Die Alkaloide1 und4 besitzen schwache antimikrobielle Aktivität.

     

Ozonolyse von Olefinen,III: Säurekatalysierte Ozonolyse von 3-Hexen-1,6-und 2-Penten-1,5-dicarbonylderivaten

Summary The ozonolysis of mono-unsaturated compounds containing the structural element =CH-CH₂-R [R=COOH, COOCH₃, CH(OCH₃)₂] was investigated. Reductive ozonolysis of (E)-3-hexene-1,6-dioic acid gives methyl 3,3-dimethoxypropanoate (2), whereas ozonolysis of dimethyl (E)-3-hexene-1,6-dioate (1a) and (Z)-1,1,6,6-tetramethoxy-3-hexene (1b) in a methanolic solution of HCl leads to a mixture of2, dimethyl malonate (3 a) and 1,1,3,3-tetramethoxypropane (3 b). The homologuos derivatives, dimethyl glutaconate (4 a) and 1,1,5,5-tetramethoxy-2-pentene (4 b), were ozonized to give mixtures of2, 3, dimethyl oxalate (5), methyl 2,2-dimethoxyacetate (6 a), and 1,1,2,2-tetramethoxyethane (6 b). The ratios of the various reaction products were determined by gas chromatography. In each case the formation of the bifunctional derivatives2 and6 a was favoured.

     

Syntheses of pyridin-4-ylium chirons: applications in a synthesis of (+)-coniine

The compounds (3R,5S)-(+)-5-methyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide 4 and (3R,5S)-(+)-5-n-propyl-3-phenyl-2,3,5,6,7,8-hexahydro-oxazolo[3,2-a]pyridin-4-ylium iodide 5 were synthesized in two steps starting from the bicyclic thiolactam trans (3R,2aS)-(−)-5-thio-3-phenyl-2,3,6,7,8,2a-hexahydro-oxazolo[3,2-a]pyridine 1. In addition, starting from 5 an enantiospecific synthesis of (+)-coniine 7 was achieved.     

Total syntheses of the sesquiterpenoids (+)-trans-dracunculifoliol and (+)-4-hydroxyoppositan-7-one

Sesquiterpenoids (+)-trans-dracuncuflifoliol (1) and (+)-4-hydroxyoppositan-7-one (2) were prepared stereoselectively from enantiomerically pure (7aR)-7a-methyl-1,2,5,6,7,7a-hexahydro-4H-inden-4-one ((−)-6), whose synthesis was described herein. Conjugate addition of the organocopper (I) reagent 10 to (−)-6, followed by epimerization of the ring junction, generated 3 of the 4 contiguous chiral centers of both natural products.