Yu-Lin Wu

Convenient syntheses of tonghaosu and two thiophene substituted spiroketal enol ether natural products

A convenient synthetic method of spiroketal enol ether by dehydration-spiroketalization reaction from furan intermediate and its application for the syntheses of three natural products, tonghaosu (1) and 2, 3, was reported.

A STRAIGHTFORWARD SYNTHETIC APPROACH TO THE SPIROKETAL-ENOL ETHERS SYNTHESIS OF NATURAL ANTIFEEDING COMPOUND TONGHAOSU AND ITS ANALOGS

Abstract Tonghaosu 1 , a natural product discovered from several plants of tribe Athemdeae , is a [4.4]spiroketal with an enediyne side-chain and shows interesting insect antifeeding activity. In this paper a general and convenient synthetic methodology for the synthesis of 1, 2 and its spiroketal-enol ether derivatives is described. Thus, 3-(2′-furyl)-propan-1-ol 7a or 4-(2′-furyl)-butan-1-ol 7b prepared from furaldehyde was treated with n -butyl lithium and unsaturated aldehyde to provide the diol 5 . Diol 5 could also be obtained from 5-(3-acetoxypropyl)-2-furaldehyde or 5-(4-acetoxybutyl)-2-furaldehyde and alkynyllithium. By careful treatment of 5 or 7 with acid, dehydration-cyclization occurred to give the desired spiroketal-enol ether in moderate to excellent yields.

A stereospecific synthesis of L-deoxyribose, L-ribose and L-ribosides

Abstract Using an inexpensive d -galactose from the chiral pool, l -deoxyribose, l -ribose and their derivatives were synthesized via mild reaction conditions. During the synthesis of l -deoxyribose, the key deoxygenation of the 2-hydroxy group of 3,5-O-dibenzyl-methyl- l -arabinofuranoside was performed by reduction of the corresponding triflate with tetrabutylammonium borohydride in high yield. During the synthesis of l -ribose, the key step of inversion of the 2-hydroxy group in the same substrate was carried out by intramolecular SN2 tandem reaction. Then the l -ribosyl donors were submitted to glycosidations according to Vorbruggens conditions to give l -ribosides ( l -uridine, l -5-fluorouridine, l -iodouridine, l -thymidine, l -puridine, l -adenosine and l -guanosine) in excellent yields.

An efficient method for synthesis of α-keto acid esters from terminal alkynes

α-Keto acid esters can be easily prepared in high yields in two steps from terminal alkynes via bromination and oxidation. This strategy provides a versatile access to the synthesis of biologically important natural products with an α-keto acid moiety.

Structure determination and synthesis of a new cerebroside isolated from the traditional Chinese medicine Typhonium giganteum Engl.

Abstract A new cerebroside with C18-4,8-sphingadienine as the long chain base has been isolated from the traditional Chinese medicine Typhonium giganteum Engl., and its structure was determined by 2D NMR and MS methods. It was then synthesized using d -xylose and ascorbic acid as the chiral starting materials.

Synthesis of 3-deoxy-2-ulosonic acid KDO and 4-epi-KDN, a highly efficient approach of 3-C homologation by propargylation and oxidation

Through the introduction of a pyruvate segment by asymmetric propargylation and oxidation of terminal alkynes, both KDO and 4-epi-KDN have been concisely synthesized in the furanose form from readily available sugars in high overall yields.

A stereospecific synthesis of l-ribose and l-ribosides from d-galactose

Abstract An inexpensive d -galactose was converted into l -ribose and its derivatives via mild reaction conditions. The l -ribosyl donor was submitted to a glycosidation according to Vorbruggens conditions to give l -ribosides in high yields.

Study on the mechanism of action of artemether against schistosomes: the identification of cysteine adducts of both carbon-centred free radicals derived from artemether.

Reaction of the antimalarial and anti-schistosome drug artemether (1) and catalytic amount of ferrous ion in the presence of excess cysteine gave two adducts of cysteine and previous postulated primary and secondary carbon-centred free radicals besides their other rearrangement products. This piece of further evidence for the presence of carbon-centred radicals, especially the secondary carbon-centred free radical for the first time by the isolation of its coupling adduct, will be help to understand the mechanism of action of artemether and other qinghaosu derivatives against parasites.

Synthetic study on chiral building block of vicinal diol, chiron approach to the precursors of all sphingosine stereoisomers

Abstract All enantiomeric stereoisomers of 1,2,3-trihydroxy-4E-octadecene, key intermediates for the syntheses of sphingosines were prepared using sugar as chiral pool

Synthesis and glycosylation of thio-D-fructofuranoside donors

Two ethyl thioglycosides of D-fructofuranose 4a and 4b, synthesized from D-arabinose and differentially protected at position 1 and 6, react with bulky acceptors in the presence of IDCP giving only α-frucofuranosides in essentially quantitative yields.