Rapid parallel liquid-phase synthesis of pyrazoles has first been developed. The 1,3-dipolar cycloaddition be-tween nitrilimines generated in situ and soluble polymer-supported alkynyl or alkenyl dipolarophiles in parallel one-pot fashion gave the corresponding PEG-supported regioisomeric pyrazoles or regiospecific pyrazolines. The latter was assuredly oxidated by DDQ to PEG-supported regiospecific pyrazoles. Cleavage from the support under mild conditions afforded pyrazoles in good yields and high purity.
A rapid and facile synthesis of N-substituted 2,3,3a,4,7,7a-hexahydroisoindole-l,3-dione derivatives via microwave-promoted Beller three-component domino reaction of α,β,-unsaturated aldehydes, amides and N-substituted maleimides was described.
A novel method for the enantioselective synthesis of β-lactams is described in this study. 2,3-Dihydrobenzooxazin-4-one derived from salicylamide and L-menthone was used as the chiral auxiliary, which reacted with a-bromo-acyl bromides in the presence of pyridine to give carboximides 2. The stereo-controlled Reformatsky-type reactions of carboximides with imines yielded the corresponding trans β-lactams with high enantioselectivities（e.e. 75%-86%） and high chemical yields（63%-85%）, meanwhile, the chiral auxiliary dihydrobenzooxazin-4-one was released and recovered.
Recent evidence has accumulated suggesting that free radicals are involved in many deterioration processes. They attack the unsaturated fatty acids in the biomembranes resulting in membrane lipid peroxidation, which is strongly connected with aging, carcinogenesis and atherosclerosis.[1] Free radicals also attack DNA and cause mutation leading to cancer.[2] Thus it is desirable to look for effective radical scavengers. In 1999, Gao et al.[3] isolated incanosides C, D and E from the whole plant of Caryopteris incana (THUNB.). These natural products were proved to exhibit good radical scavenging activities against DPPH radical and inhibitory activities against the oxidation of linoleic acid.[4] Herein, for the first time we report the synthesis of trisaccharide phenyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl-(1→2)-3,4-di-O-benzoyl-α-L-rhamno-pyranosyl-(1→3)-2-O-acetyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside (1), which is the common carbohydrate moiety of incanosides C, D and E.……
A facile, rapid and regioselective method for the 1-O-deacylation of peracylated glycopyranoses is described which occurs under mild conditions by absorption onto alumina using microwave irradiation.
Jia Qiang DONG, Shu Jia ZHANG, Yan Guang WANG Department of Chemistry, Zhejiang University, Hangzhou 310027
