Concise total synthesis of (+)-carpamic acid

We report herein an efficient enantioselective synthesis of (+)-carpamic acid, with nine steps as the longest linear sequence, the key strategy being based on a novel sequence of a cross-metathesis (CM) reaction and a subsequent cyclizing reductive amination to form the piperidine ring.     

Concise total synthesis of flavone C-glycoside having potent anti-inflammatory activity

The total synthesis of anti-inflammatory active flavone C-glycoside isolated from oolong tea extract is achieved. Introducing a C-glucosyl moiety to an aryl system and constructing a fused tetracyclic ring characteristic to this natural product were conducted based on the O-to-C rearrangement of sugar moiety and the successive intramolecular Mitsunobu reaction, respectively. This concise and efficient synthetic pathway is applicable to the large-scale synthesis of target flavone and for constructing a large library of related compounds.     

Concise synthesis of ether analogues of lysobisphosphatidic acid

We describe a versatile, efficient method for the preparation of ether analogues of (S,S)-lysobisphosphatidic acid (LBPA) and its enantiomer from (S)-solketal. Phosphorylation of a protected sn-2-O-octadecenyl glyceryl ether with 2-cyanoethyl bis-N,N-diisopropylamino phosphine and subsequent deprotection generated the bisether LBPA analogues. By simply changing the sequence of deprotection steps, we obtained the (R,R)- and (S,S)-enantiomers of 2,2'-bisether LBPA. An ELISA assay with anti-LBPA monoclonal antibodies showed that the bisether LBPAs were recognized with the same affinity as the natural 2,2'-bisoleolyl LBPA. [reaction: see text]     

Concise enantioselective synthesis of abscisic acid and a new analogue

Short and high-yielding syntheses of enantiomerically pure (S)-(+) and (R)-(-)-abscisic acid are described. The syntheses proceed through key intermediates that preferentially recrystallise as single diastereoisomers for each enantiomer. This route allows the preparation of either enantiomer of abscisic acid in ca. 30% overall yield, and as demonstrated, gives access to an enantiomerically pure abscisic acid analogue.     

Concise synthesis of acyl migration-blocked 1,1-difluorinated analogues of lysophosphatidic acid

Lysophosphatidic acid (LPA, 1- or 2-acyl-sn-glycerol 3-phosphate) is an important phospholipid mediator produced by activated platelets and by ovarian cancer cells. Efforts to understand LPA signaling through G-protein-coupled receptors are hampered by the facile acyl migration that results in equilibration to a mixture of the 1- or 2-acyl species under physiological conditions. We describe a new and efficient route to enantiomerically homogeneous lysophospholipid analogues from D-mannitol 1,2:5,6-bis-acetonide to give two 1,1-difluorodeoxy analogues of (2R)-acyl-sn-glycerol 3-phosphate. These compounds are migration-blocked analogues of the labile sn-2 LPA species. The (19)F NMR of diastereotopic fluorines of the difluoromethyl group shows an unexpected solvent dependence.     

Concise synthesis of dl-febrifugine

Racemic compound (1) of the antimalarial agents febrifugine (d-1) was synthesized using an stereoselective Michael reaction of an omega-amidoenone (5) which was prepared by the Wittig reaction of piperidinediol (7).     

脂肪酶催化合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯

用固定化脂肪酶Lipozyme 435作催化剂,分别用直接酯化法和酯交换法合成L-抗坏血酸脂肪酸酯和D-异抗坏血酸脂肪酸酯.产物结构经IR、1HNMR、13CNMR和MS表征.结果表明,对于同一目标化合物,相似条件下,直接酯化法的效果优于酯交换法,原料脂肪酸和脂肪酸甲酯均可回收循环使用.     

Concise and highly selective asymmetric synthesis of acosamine from sorbic acid

Diastereoselective conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to tert-butyl sorbate and subsequent chemo- and diastereoselective ammonium-directed olefinic oxidation of the resultant conjugate addition product {tert-butyl (3S,αR)-3-[N-benzyl-N-(α-methylbenzyl)amino]hex-4-ene} have been used as the key steps in a concise and highly selective asymmetric synthesis of the 2,3,6-trideoxy-3-aminohexose l-acosamine. This sequence of two chemical operations allows rapid assembly of the molecular architecture and facilitates the de novo asymmetric synthesis of methyl N,O-diacetyl-α-l-acosaminide in only 7 steps from commercially available sorbic acid in 15% overall yield.     

Concise synthesis of the xenibellols core

We describe herein a concise synthesis of an intermediate, via 2,3-Wittig rearrangement and Williamson etherification, en route to the natural products, xenibellols A and B.     

A new three-step procedure for the synthesis of cyanuric acid from urea

A new procedure for preparing high-purity cyanuric acid from urea was suggested and experimentally checked. The procedure is based on urea silylation, followed by pyrolysis of the silyl derivative and fractional distillation of the trimethylsilyl isocyanate formed, for which the temperature limits of mild hydrolysis were determined.     

Simple thin-layer chromatographic purification procedure for the determination of cholesterol ester fatty acid compositions

A mild procedure for the purification of methyl esters of the fatty acid components of cholesterol esters, from interfering free cholesterol and other contaminating residues, is described. Methyl esters and free cholesterol are formed during the methylation of cholesterol esters. When co-extracted, cholesterol and other contaminating residues interfere with the methyl esters because minute proportions of these residues tend to elute at the same retention times as palmitoleic and stearic acids, to yield unreliable but significantly higher values for palmitoleic (p less than 0.001) and stearic acids (p less than 0.0001), and correspondingly lower values for oleic acid (p less than 0.0001). Purification of methyl esters by thin-layer chromatography eliminates this problem and yields reliable analysis of cholesterol ester fatty acids, without measurable oxidation of unsaturated fatty acids.     

Concise enantioselective synthesis of furocaulerpin

The first total synthesis of both enantiomers of furocaulerpin was accomplished in good yields with a high control of the stereogenic center by enzymatic resolution, a total control of the configuration of the central double bond and the construction of the dienyne moiety via a Stille cross-coupling.     

Concise synthesis of omega-borono-alpha-amino acids

A short protocol for the practical scale synthesis of several omega-borono-alpha-amino acids is described via the alkylation of benzophenone glycinimines with various electrophiles.     

Concise synthesis of 1-epi-castanospermine

1-epi-Castanospermine (5) was synthesized from readily available 2,3,4,6-tetra-O-benzyl-1-deoxynojirimycin (11) in 9 steps and 21% overall yield, with selective debenzylation, Barbier reaction and reductive amination as the main reaction steps.     

Rapid procedure for the isolation and analysis of fatty acid and fatty alcohol fractions from wax esters of marine zooplankton

A rapid and simple method for the isolation of fatty acid methyl esters and fatty alcohols from the lipid fraction of marine zooplankton is described. Wax esters are the dominant lipid class in most calanoid copepods and trans-esterification results in a high fatty alcohol content in the analytical extract. Current procedures for the separation and purification of lipid classes by preparative thin-layer chromatography are time-consuming and are subject to low recovery of the analytes. In this method, fatty acid methyl esters and fatty alcohols were separated by liquid chromatography using silica or honded amino-silica as the stationary phase. The procedure is equally applicable to the analysis of zooplankton with low wax ester (and hence fatty alcohol) content, for example, a number of species of euphausiid and, generally, for samples of low mass.     

Concise synthesis of two advanced intermediates for the asymmetric synthesis of polyhydroxylated indolizidine alkaloids

A concise five-step approach to indolizidinones 10 and 11, two advanced intermediates for the asymmetric synthesis of polyhydroxylated indolizidine alkaloids, has been developed by using N-Cbz pyrrolidin-2-yl pyridin-2-yl sulfide 13 as the chiral building block. The method features a SmI₂-mediated coupling of sulfide 13 with functionalized aldehyde 14 and a tandem N-deprotection-lactamization, which constitutes a stepwise “2 + 4” annulation method for the construction of the indolizidinone ring system of 12a.     

Preparation and thin-layer chromatography of bromo-derivatives of unsaturated fatty acid esters. A simple and rapid procedure for fatty acid analysis.

Bromo-addition products of unsaturated long-chain fatty acid esters have been prepared and chromatographed on thin layers of unmodified silica gel. The polarity of these derivatives was found to be directly related to the number of double bonds of the parent fatty acid from which they were derived. This has been made the basis of a simple method for assessing the relative proportions of the main fatty acid classes in a mixture.