Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Verbindungen. III. Synthese von (+)-Abscisinsäure, (−)-Xanthoxin, (−)-Loliolid, (−)-Actinidiolid und (−)-Dihydroactinidiolid

Synthesis of optically active natural carotenoids and structurally related compounds. III. Synthesis of (+)-abscisic acid, (?)-xanthoxin, (?)-loliolide, (?)-actinidiolide, and (?)-dihydroactinidiolide The syntheses of (+)-abscisic acid ( 1 ), (?)-xanthoxin ( 2 ), (?)-loliolide ( 3 ), (?)-actinidiolide ( 4 ), and of (?)-dihydroactinidiolide ( 5 ) from one common starting material are reported. The syntheses yield also some enantiomeric or diastereomeric analogues.     

Sesquiterpenoids from Costus Root Oil (Saussurea lappa CLARKE)

Apart from the well-known constituents (+)-β-selinene ( 2 ), (?)-β-elemene ( 4 ), (+)-β-costol ( 7 ), (?)-caryophyllene ( 17 ), and (?)-elemol ( 19 ) the following sesquiterpenoids have been isolated for the first time from costus root oil (Saussurea lappa CLARKE ): (?)-α-selinene ( 1 ), (+)-selina-4, 11-diene ( 3 ), (?)-α-trans-bergamotene ( 5 ), (?)-α-costol ( 6 ), (+)-γ-costol ( 8 ), (?)-elema-1,3,11 (13)-trien-12-ol ( 9 ), (?)-α-costal ( 11 ), (+)-γ-costal ( 12 ), (+)-γ-costal ( 13 ), (?)-elema-1,3,11 (13)-trien-12-al (elemenal, 14 ), (?)-(E)-trans-bergamota-2, 12-dien-14-al ( 15 ), (?)-ar-curcumene ( 16 ), and (?)-caryophyllene oxide ( 18 ). Compounds 6 , 8 , 9 , and 13 are new sesquiterpenoids. IR. and NMR. spectra of 12 sesquiterpenoids are reproduced.     

3,5,6-三-氧-甲基-D-葡萄糖与N-取代甘氨酸乙酯反应中的Amadori重排

Amadori重排是胺(包括氨基酸)与还原糖间一系列复杂反应中的很重要的一步,反应。一级胺以及二级芳香胺与还原糖反应中的Amadori 重排已有大量报道,但对涉及二级脂肪胺特别是 N-取代氨基酸的报道却为数甚少。Anet 曾报道了 N-取代甘氨酸与葡萄糖作用后,得到 Amadori 重排产物的结果,但对其作用机制及反应中间产物无详细描述。本文研究了 N-取代甘氨酸乙酯与3,5,6-三-氧-     

Preparation and Absolute Configuration of (−)-(E)-α-trans-Bergamotenone

The synthesis, absolute configuration, and olfactive evaluation of (?)-(E)-α-trans-bergamotenone (= (?)-(1′S,6′R,E)-5-(2′,6′-dimethylbicyclo[3.1.1]hept-2′-en-6′-yl)pent-3-en-2-one; (?)- 1 ), as well as its homologue (?)- 19 are reperted. The previously arbitrarily attributed absolute configuration of 1 and of (?)-α-trans-bergamotene (= (?)-(1 S,6R)-2,6-dimethyl-6-(4-methylpent-3-enyl)bicyclo[3.1. 1]hept-2-ene; (?)- 2 ), together with those of the structurally related aldehydes (?)- 3a,b and alcohols (?)- 4a,b , have been rigorously assigned.     

An easy preparation of (−) and (+)-β-piperonyl-γ-butyrolactones,key-intermediates for the synthesis of optically active lignans

Methyl α-piperonylhemisuccinate was resolved into both its (R)-(+) and (S)-(?)-antipodes by (?) and (+)-ephedrine, respectively. Calcium borohydride reduction of the (R)-(+) and (S)-(?)-hemiesters afforded the crystalline, optically pure, (R)-(+) and (S)-(?)-β-piperonyl-γ-butyrolactones, respectively, and in high yields. The latter were converted into (?) and (+)-isodeoxypodophyllotoxin, respectively.     

Redox Divergent Synthesis of Fawcettimine‐Type Lycopodium Alkaloids

A new approach for synthesis of fawcettimine‐type Lycopodium alkaloids is described. A divergent strategy was achieved by applying stereoselective Diels–Alder reaction followed by redox‐controlled elaboration. Eventually, (?)‐8‐deoxyserratinine, (+)‐fawcettimine, (?)‐lycopoclavamine‐A, (?)‐serratine, (?)‐lycopoclavamine‐B and (?)‐serratanidine were successfully accessed.     

Kinetic determination of microquantities of D(−)-arabinose

A kinetic method for the determination of microquantities of d(?)-arabinose is presented. The method is based on the accelerating effect of d(?)-arabinose on the reaction between molybdenum(VI) and hydrogen peroxide in solution containing 50 vol% of acetonitrile. In order to find optimum experimental conditions for the determination of d(?)-arabinose, the kinetics of the reaction between molybdenum(VI) and hydrogen peroxide in the presence, as well as in the absence, of d(?)-arabinose was studied. d(?)-Arabinose was determined photometrically by following the rate of the colored reaction product formation. The concentrations of d(?)-arabinose which were determined ranged from 46 to 135 μg/ml, and the standard deviation was lower than 10%.     

Enantioselective synthesis of orthogonally protected (2R,3R)-(−)-epicatechin derivatives,key intermediates in the de novo chemical synthesis of (−)-epicatechin glucuronides and sulfates

Ten orthogonally protected (?)-epicatechin and 3′- or 4′-O-methyl-(?)-epicatechin derivatives were prepared in a regiospecific and enantioselective manner. For each orthogonally protected (?)-epicatechin derivative, one specific phenolic hydroxyl was protected with a methoxymethyl (MOM) or p-methoxybenyzl (PMB) group and the remainder were protected as benzyl ethers. These uniquely protected (?)-epicatechin derivatives were designed to facilitate the regiospecific installation of a glucuronic acid or sulfate unit onto (?)-epicatechin after selective removal of the MOM or PMB protecting group to provide authentic standards of (?)-epicatechin glucuronides and sulfates.     

Synthesis of [4.3.3]Propellanes by Carbenium‐Ion Rearrangement and Their Olfactory Characterization

Treatment of (+)‐sclareolide ( 1 ) with polyphosphoric acid or Eaton's reagent furnished, besides the anticipated cyclopentenone (?)‐ 12 and its isomer (?)‐ 15 , two diastereoisomeric [4.3.3]propellanes (?)‐ 13 and (?)‐ 14 , which possess interesting woody‐ambery odors. The hydrogenated derivative (?)‐ 17 possessed an even more‐powerful odor reminiscent of natural ambergris tincture. Mechanistic insight into this rearrangement was provided by a by‐product 24 of the reaction of sclareolide ( 1 ) with Eaton's reagent. The carbenium ion rearrangement was then employed in the synthesis of four related [4.3.3]propellanes 40 – 43 , illustrating the utility and scope of this reaction. The olfactory properties of the synthesized [4.3.3]propellanes as well as of the original target structures 10, 33 , and 34 , prepared from (?)‐ 12 and (?)‐ 15 , are discussed. Especially the pronounced ambra odor of (?)‐ 17 vividly contradicts the ‘triaxial rule of amber sensation' and provides new insight into the structural requirements for ambra odorants.     

Reaction of sulphoximides with diazomalonate in the presence of Cu-salt : A new synthesis and stereochemistry of optically active oxosulphonium ylides

Sulphoximides (Ia–Ie) were found to react with dimethyl diazomalonate (DDM) in the presence of a catalytic amount of Cu-salts affording the corresponding oxosulphonium ylides in moderate yields. The reaction did not proceed at all under irradiation of UV light. (?)-Methylphenyloxosulphonium bis(methoxycarbonyl)-methylide ((?)-IIb) was obtained from (+)-(S)-methylphenylsulphoximide ((+)-(S)-Ib) together with (?)-(S)-methyl phenyl sulphoxide ((?)-(S)-IIIb) by this reaction. Hydrolysis of (?)-IIb gave (+)-methylphenyloxosulphonium methoxycarbonylmethylide ((+)-IIf) which was converted to (?)-(S)-IIIb upon treatment with dibenzoylethylene. Stereochemical cycle starting from (+)-(S)-Ib to (?)-(S)-IIIb was established and the absolute configurations of both ylides, (?)-IIb and (+)-IIf were assigned as (R)-configuration. The stereochemical courses, namely from (+)-(S)-Ib or (?)-(S)-IIIb to (?)-(R)-IIb or (+)-(R)-IIf to (?)-(S)-IIIb were determined as retention processes. The optical purities of the oxosulphonium ylides obtained from both reactions, (+)-(S)-Ib→(?)-(R)-IIb and (?)-(S)-IIIb→(?)-(R)-IIb, were almost equal. These results indicate that the mechanism of the reaction of sulphoximides with carbenes (or carbenoids) involves the initial formation of the sulphoxides which react subsequently with carbenes to afford the final products.     

The racemization of an optically active sulfilimine and optically active aminosulfonium salts

The racemization of an optically active sulfilimine and optically active aminosulfonium salts was kinetically measured. The mechanism of the racemization of optically active sulfilimine (?)-1 has been established. The activation parameters for the racemization of (?)-1 and (?)-7 were calculated. A plausible pathway for the decomposition of (?)-6, (?)-7 and (?)-8 with tetra-n-butylammonium bromide in the presence of methyl ethyl ketone to provide 3-p-tolylthio-2-butanone 22 is proposed.     

Synthesis and optical properties of polyethylenimine containing L-proline and optically active thymine derivatives

Preparation and optical properties of linear polyethylenimine (PEI) containing L -(?)-N-[(?)-2-(thymin-1-yl) propionyl] prolyl group as grafting pendant, [P-(?)Pro-(?)T], and its related monomer and dimer model compounds are described. Hypochromic effects and circular dichroism of these compounds were compared with those of PEI containing (?)-2-(thymin-1-yl) propionyl group as grafting pendant, [P-(?)T], which has no L -proline ring as a spacing group. P-(?)Pro-(?)T showed no exciton coupling of B_2u π-π^* transition although it showed large hypochromicity in neutral aqueous solution, implying that the stacking of the bases has no screw sense.     

Total Syntheses of (−)‐Strictosidine and Related Indole Alkaloid Glycosides

A collective synthesis of glycosylated monoterpenoid indole alkaloids is reported. A highly diastereoselective Pictet–Spengler reaction with α‐cyanotryptamine and secologanin tetraacetate as substrates, followed by a reductive decyanation reaction, was developed for the synthesis of (?)‐strictosidine, which is an important intermediate in biosynthesis. This two‐step chemical method was established as an alternative to the biosynthetically employed strictosidine synthase. Furthermore, after carrying out chemical and computational studies, a transition state for induction of diastereoselectivity in our newly discovered Pictet–Spengler reaction is proposed. Having achieved the first enantioselective total synthesis of (?)‐strictosidine in just 10 steps, subsequent bioinspired transformations resulted in the concise total syntheses of (?)‐strictosamide, (?)‐neonaucleoside A, (?)‐cymoside, and (?)‐3α‐dihydrocadambine.     

Notiz zur Konstitution des Laurepukins. 8. Mitteilung über natürliche und synthetische Isochinolin-Derivate

The alkaloid (?)-laurepukine is shown to possess one of the epimeric N-oxide structures 4 or 5 . Oxidation of (?)-pukateine ( 3 ) by hydrogen peroxide gives (?)-laurepukine and, as a second product, 6-epi-laurepukine.     

Stereoselective total synthesis of (−)-zeylenol,a key intermediate for the synthesis of (+)-pipoxide, (−)-uvarigranol G and (−)-tonkinenin A

Total synthesis of (?)-zeylenol, a key intermediate for the synthesis of (+)-pipoxide, (?)-uvarigranol G and (?)-tonkinenin A was achieved from commercially available starting material d-mannose. The key steps are mixed aldol condensation, Grignard reaction, ring closing metathesis and regioselective benzoylation.     

Structures and synthesis of some new antibacterial sesquiterpenoids from the gorgonian coral Pseudopterogorgia rigida

The antibacterial properties of extracts of the Caribbean gorgonian Pseudopterogorgia rigida have been shown to originate in three previously undescribed derivatives of the aromatic sesquiterpene α-curcumene. (?)-Curcuphenol, (?)-curcuquinone, and (?)-curcuhydroquinone were isolated in high yield (30% extract) and structurally defined by inter-conversion and by reduction of the mesylate derivatives to yield the parent hydrocarbon (?)α-curcumene. A high yielding synthesis (86% overall) of curcuphenol, the most active antibacterial metabolite, is described.     

Divergent Total Syntheses of (−)‐Daphnilongeranin B and (−)‐Daphenylline

(?)‐Daphnilongeranin B and (?)‐daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (?)‐daphnilongeranin B and a bioinspired synthesis of (?)‐daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late‐stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.     

Contribution à la connaissance des o-menthols et des o-menthones (carquéjanols et carquéjanones). 3e communication

The alcohols (+)-carquejanol, (?)-neocarquejanol, (?)-isocarquejanol, and (?)-neoisocarquejanol are described, and their conformations and configurations are studied by IR., NMR. and mass spectroscopies. Isocarquejanol is a mixture of conformers approximatively 50:50 with, respectively, axial and equatorial OH.     

Stereoselective synthesis of pinane-based β- and γ-amino acids via conjugate addition of lithium amides and nitromethane

Michael addition of dibenzylamine to (?)- and (+)-tert-butyl myrtenate, (?)-2 and (+)-2, derived from (?)- and (+)-myrtenal, furnished monoterpene-based β-amino acid derivatives in highly stereospecific reactions. The resultant amino esters (?)-3 and (+)-3 were transformed to unsubstituted, mono- and disubstituted and Fmoc-protected amino acids (?)-6-11 and (+)-6-11, which are promising building blocks for the synthesis of β-peptides and 1,3-heterocycles. The microwave-assisted conjugate addition of nitromethane to α,β-unsaturated esters (?)-12 and (+)-12 likewise resulted in nitro esters (?)-13 and (+)-13 in highly stereospecific reactions. Compounds (?)-13 and (+)-13 were successfully transformed into γ-amino acids (?)-16 and (+)-16 in two steps.     

Total Syntheses of (−)‐Isoschizogamine and (−)‐2‐Hydroxyisoschizogamine

Total syntheses of (?)‐isoschizogamine and (?)‐2‐hydroxyisoschizogamine are described. The synthesis employs two asymmetric Michael additions to establish chiral centers at C7 and the quaternary carbon C20. Regioselective reduction of the methylthioiminium cation rather than the enamine generates an isoschizogamine‐type pentacyclic skeleton. Acidic hydrolysis of the isoschizogamine‐type intermediate in the absence of oxygen provides natural (?)‐isoschizogamine. Conducting the reaction in the presence of oxygen leads to a multistep oxidative hydrolysis cascade that affords unnatural (?)‐2‐hydroxyisoschizogamine.