Identification de la damascénone et de la β-damascone dans le tabac Burley

The successful identification of damascenone (I)

1 DORICENONE (trade mark of Firmenich & Cie, Geneva).

and β-damascone (III)

2 DORINONE (trade mark of Firmenich & Cia, Geneva)

in Burley tobacco oil was achieved through the use of an efficient vapour phase chromatography/mass spectrometry combination. Thus, the occurrence of β-damascone in nature and the presence of damascenone in an essential oil not related to rose oil were demonstrated.     

New Preparation Methods for α‐Damascone, γ‐Damascone,and β‐Damascenone using Pyronenes

γ‐ and δ‐Pyronenes are terpenic synthons easily available from myrcene. They are used as intermediates in the synthesis of α‐damascone, γ‐damascones, and β‐damascenone.     

Convenient procedure for the preparation of alkyl and aryl substituted N-(aminoalkylacyl)sulfonamides

A convenient synthesis of N-(aminoalkylacyl)sulfonamides from CBZ potected glycine, β-alanine and GABA is described.     

Enantioselective total synthesis of macrosphelides A and E

Enantioselective synthesis of 16-membered trilactone macrolides, macrosphelide A and E from (S)-lactic acid is described. Key features of the synthesis include the utility of a hitherto unexplored β-ketophosphonate derived from lactic acid and Yamaguchi lactonization leading to the title compounds.     

A new synthesis of thioflavones

A new synthesis of thioflavones from β-keto sulphoxide (12) is described.     

A one-pot combination of amine and heterocyclic carbene catalysis: direct asymmetric synthesis of β-hydroxy and β-malonate esters from α,β-unsaturated aldehydes

The one-pot combination of amine and heterocyclic carbene catalysis (AHCC) enabled the synthesis of β-hydroxy, β-malonate and β-amino esters from α,β-unsaturated aldehydes with high enantioselectivity (91-97% ee).     

One pot direct synthesis of β-ketoesters via carbonylation of aryl halides using cobalt carbonyl

A direct method for the synthesis of β-ketoesters from aryl halides (iodide, bromide) has been described by using cobalt carbonyl as carbon monoxide source in microwave irradiation. Using this protocol, a wide variety of substituted aryl halides has been successfully converted to corresponding β-ketoesters.     

Enantioselective synthesis of (-)-basiliskamide A

Basiliskamide A is an antifungal polyketide natural product isolated by Andersen and co-workers from a Bacillus laterosporus isolate, PNG-276. A nine-step enantioselective synthesis of (-)-basiliskamide A is reported, starting from commercially available β-hydroxy ester 7. The synthesis features a highly diastereoselective mismatched double asymmetric δ-stannylallylboration reaction of aldehyde 5 with the bifunctional allylborane reagent 4.     

A synthesis of (−)-ebelactones A and B

A synthesis of the β-lactone esterase inhibitors (−)-ebelactones A and B is described. The synthesis features the use of a Hoppe homoaldol reaction and a Cu(I)-mediated 1,2-metallate rearrangement of a metallated enol carbamate as key fragment linkage reactions.     

Bioinspired total synthesis and human proteasome inhibitory activity of (-)-salinosporamide A, (-)-homosalinosporamide A, and derivatives obtained via organonucleophile promoted bis-cyclizations

A full account of concise, enantioselective syntheses of the anticancer agent (-)-salinosporamide A and derivatives, including (-)-homosalinosporamide, that was inspired by biosynthetic considerations is described. The brevity of the synthetic strategy stems from a key bis-cyclization of a β-keto tertiary amide, which retains optical purity enabled by A(1,3)-strain rendering slow epimerization relative to the rate of bis-cyclization. Optimization studies of the key bis-cyclization, enabled through byproduct isolation and characterization, are described that ultimately allowed for a gram scale synthesis of a versatile bicyclic core structure with a high degree of stereoretention. An optimized procedure for zincate generation by the method of Knochel, generally useful for the synthesis of salino A derivatives, led to dramatic improvements in side-chain attachment and a novel diastereomer of salino A. The versatility of the described strategy is demonstrated by the synthesis of designed derivatives including (-)-homosalinosporamide A. Inhibition of the human 20S and 26S proteasome by these derivatives using an enzymatic assay are also reported. The described total synthesis of salino A raises interesting questions regarding how biosynthetic enzymes leading to the salinosporamides proceeding via optically active β-keto secondary amides, are able to maintain the stereochemical integrity at the labile C2 stereocenter or if a dynamic kinetic resolution is operative.     

Concise synthesis and revision of the proposed biogenesis of helicascolides

A concise synthesis of helicascolides A, B and C was achieved in three to five steps from commercially available materials. The key transformations of the synthesis include an Evans-Metternich anti-aldol reaction of the known β-keto imide 10 and strategic base-mediated one-pot cyclization/alkylation. Based on the new chemical evidence of ring-opening reaction of β-keto ester under biocompatible basic conditions, Krohn’s proposal for the biosynthetic relationship between helicascolide A (1) and a naturally co-existing acyclic dienone 4 was suggested in a reverse manner.     

Synthesis and evaluation of a broad range of new chiral phosphine–carbene ligands for asymmetric hydrogenation

A straightforward and gram scale synthesis (six-step synthesis from enantioenriched β-hydroxy esters) of new structurally simple phosphine-carbene ligands bearing a single stereogenic centre has been achieved. Enantioselectivities of up to 60-63% could be achieved in the hydrogenation of methylstilbene and dehydroaminoacids when the reactions were performed under 20-50 bar hydrogen pressure.     

Practical synthesis of β-acyl and β-alkoxycarbonyl heterocyclic sulfones

A short and efficient synthesis for β-acyl and β-alkoxycarbonyl heterocyclic sulfones containing benzothiazol (BT) and phenyltetrazol (PT) heterocyclic core is presented here. The method seems to be general and provides the desired C-nucleophiles in very good to excellent yields from readily available starting materials.     

Simple, facile and one-pot conversion of the Baylis-Hillman acetates into 3,5,6-trisubstituted-2-pyridones

A facile route for the synthesis of novel 3,5,6-trisubstituted-2-pyridones from the acetylated Baylis-Hillman esters with β-enamino esters or β-enamino nitriles in one pot with good yields is described.     

Ionic catch and release oligosaccharide synthesis (ICROS)

A general and efficient chromatography-free ionic-liquid-supported "catch-and-release" strategy for oligosaccharide synthesis (ICROS) is reported. The methodology is compatible with current glycosylation strategies and amenable to protecting group manipulations. A series of β-(1→6) and β-(1→2)-linked glycan structures have been prepared to showcase the versatility of the strategy.     

Mild and efficient one-pot synthesis of chiral β-chalcogen amides via 2-oxazoline ring-opening reaction mediated by indium metal

A simple and efficient procedure for the synthesis of β-seleno and β-thio amides via the ring-opening reaction of chiral 2-oxazolines in the presence of indium metal has been developed. Features of this method include the following: (i) easily and accessible starting materials; (ii) indium metal is more stable and less expensive then its respective salts; (iii) useful to excellent yields of β-chalcogen amides derivatives.     

Synthesis of β-amino carbonyl compounds via a Zn(OTf)2-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds

A Zn(OTf)₂-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds was described. This one-pot three-component reaction afforded the corresponding β-amino carbonyl compounds, β-amino esters, and β-amino ketones in good to excellent yields. The reaction was also applied for the liquid-phase synthesis of β-amino carbonyl compound library using PEG as a support.     

Enantioselective conjugate addition of oximes to trisubstituted β-nitroacrylates: an organocatalytic approach to β(2,2)-amino acid derivatives

A highly enantioselective organocatalytic intermolecular conjugate addition of oximes to β-nitroacrylates has been developed. The highly functionalized adducts obtained are valuable precursors for asymmetric synthesis, as demonstrated by the synthesis of β(2,2)-amino acids and oxazolidin-2-ones.     

A method of synthesis of phosphinic acids on the basis of hypophosphites: VII. Synthesis of pseudo-γ-aminobutanoyl peptides and other phosphinic analogs of γ-aminobutyric acid

A method of synthesis of pseudo-γ-aminobutanoyl peptides and other phosphinic analogs of γ-aminobutyric acid from hypophosphites is suggested. Silyl phosphonites formed by in situ addition of bis-(trimethylsilyl) hypophosphite to the corresponding α-substituted acrylates, styrene, or vinyl phosphonate used as unsaturated components in the synthesis react in situ with N-(ω-bromoalkyl)phthalimides by an Arbuzov reaction scheme, affording ω-(phthalimido)alkylphosphinic acids possessing β-substituted β-(alkoxycarbonyl)ethyl, β-phenylethyl, or β-(diethoxyphosphinoyl)ethyl substituents. Acid hydrolysis of these reaction products gives the target aminophosphinic acids: phosphinic analogs of γ-aminobutyric acid.     

Haloacetylated enol ethers. 11. Synthesis of 1-methyl- and 1-phenyl pyrazole-3(5)-ethyl esters. A one-pot procedure

A one-pot synthesis of 1-methyl- and 1-phenylpyrazole-3(5)-ethyl esters 2,3a-e by the cyclocondensation of β-alkoxyvinyl trichloromethyl ketones 1a-e with methyl and phenyl hydrazine hydrochloride under mild conditions, is reported. A study using compounds 1a-e with different substituents proved that these are versatile building blocks for the synthesis of pyrazole derivatives, having a 3(5)-ethoxycarbonyl substituent in good yields (60–89%). The hydrazine and β-alkoxyvinyl trichloromethyl ketone substituent effects on the reaction regiochemistry on the formation of the 1,3- and 1,5-isomer were observed.