A new set of completely green methods utilising air, light, water and spirulina to transform readily accessible furan substrates into a diverse range of synthetically useful polyoxygenated motifs commonly found in natural products is presented herein.
4-Methylpent-4-en-2-yn-1-ols and 6-hydroxy-2,3-dihydro-6H pyran 3-ones are condensed in different ways to a series of tricyclic dioxadienones which contain the basic framework of the cadlinolides. A mechanism of the intramolecular enyne-ene cycloisomerization and the origin of the resulting type I and type II dienes is proposed.
New procedures for the enantioselective oxidation of sulfides under stoichiometric and catalytic conditions
作者:Antonio Massa、Francesca R Siniscalchi、Valeria Bugatti、Alessandra Lattanzi、Arrigo Scettri
DOI:10.1016/s0957-4166(02)00326-9
日期:2002.7
Acid-catalyzed oxidation of 2-furylcarbinols with hydrogen peroxide affords alternatively 2-(1-hydroperoxyalkyl)furans 2 or 6-hydroperoxy-2H-pyran-3(6H)-ones 3. Compounds of the type 2 and 3 have been used Lis oxygen donors in efficient stoichiometric or catalytic procedures for the asymmetric sulfoxidation of prochiral sulfides in the presence of Ti(O-i-Pr)(4)/L-DET or Ti(O-i-Pr)(4)/(R)-BINOL/H2O systems. Positive non linear effects, (+)-NLE, were observed in the enantioselective oxidation of methyl p-tolyl sulfide, promoted by enantiomierically enriched Ti(IV)/BINOL/H2O complexes. (C) 2002 Elsevier Science Ltd. All rights reserved.
Scope and Limitations of the Photooxidations of 2-(α-Hydroxyalkyl)furans: Synthesis of 2-Hydroxy-<i>exo</i>-brevicomin
Photooxygenation of 2-(alpha-hydroxyalkyl)furans at 5 degrees C in MeOH followed by in situ reduction affords, in one synthetic operation, 6-hydroxy-3(2H)-pyranones and/or 5-hydroxy-2(5H)-furanones. The relative ratio of the final products is highly dependent on the substitution of the starting furan substrate. Photooxygenation of 2-(alpha,beta-dihydroxyalkyl)furans followed by in situ reduction and ketalization with acid rapidly provides the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework. This new methodology was successfully applied to the synthesis of 2-hydroxy-exo-brevicomin.
Synthetic Approach to Analogues of the Original Structure of Sclerophytin A
作者:Michael E. Jung、Joseph Pontillo
DOI:10.1021/jo016246j
日期:2002.9.1
is described. The beta-anomer of dideoxyribosyl nitriles 10a,b (prepared from glutamic acid) was converted into the methylketone 11. Addition of a silylated acetylide to 11 in diethyl ether/trimethylamine gave mainly 22a. Alkylation with methallyl halide and ozonolysis gave the ketone 24, which was then converted by hydrogenation and a second ozonolysis into the keto aldehyde 26. A two-step aldol process