Organocatalytic Enantiospecific Total Synthesis of Butenolides

Biologically important, chiral natural products of butenolides, (−)-blastmycinolactol, (+)-blastmycinone, (−)-NFX-2, (+)-antimycinone, lipid metabolites, (+)-ancepsenolide, (+)-homoancepsenolide, mosquito larvicidal butenolide and their analogues were synthesized in very good yields in a sequential one-pot manner by using an organocatalytic reductive coupling and palladium-mediated reductive deoxygenation or organocatalytic reductive coupling and silica-mediated reductive deamination as the key steps.     

Vinylogous Mannich reactions. Additions of trimethylsilyloxyfuran to fluorinated aldimines

Trifluoromethyl aldimines reacted with trimethylsilyloxyfuran in presence of Lewis acids to provide butenolides in high yields with total diastereoselectivity (>98%). The configuration of these products is anti. The butyrolactone 4a, substituted with a 2-trifluoromethyl ethyl amine, could be converted into a trans α-trifluoromethyl piperidine derivative.     

Enantiodivergent syntheses of γ-substituted butenolides with tertiary and quaternary asymmetric centers

Continuous nucleophilic addition with several organometallic reagents to tricyclic lactone (−)-1 proceeded diastereoselectively. Newly generated tertiary and quaternary asymmetric centers were controlled by the order in which the nucleophilic reagents were added. Using this methodology, enantiodivergent syntheses of several γ-substituted butenolides with tertiary and quaternary asymmetric centers were established from a single chiral material.     

Synthesis of Polysubstituted γ‐Butenolides via a Radical Pathway: Cyclization of α‐Bromo Aluminium Acetals and Comparison with the Cyclization of α‐Bromoesters at High Temperature

Polysubstituted butenolides were obtained in good to high yields from α‐bromoesters derived from propargyl alcohols by a one‐pot reaction involving the radical cyclization of α‐bromo aluminium acetals, followed by the oxidation of the resulting cyclic aluminium acetals in an Oppenauer‐type process and migration of the exocyclic C?C bond into the α,β‐position. Comparison with the direct cyclization of α‐bromoesters at high temperature and under high dilution conditions is described. Deuterium‐labelling experiments allowed us to uncover “invisible” 1,5‐hydrogen atom transfers (1,5‐HATs) that occur during these cyclization processes, together with the consequences of the latter in the epimerization of stereogenic centres. Compared to the classical approach, the cyclization of aluminium acetals proved to be highly chemoselective and its efficiency was illustrated by the short total syntheses of optically enriched γ‐butenolides isolated from Plagiomnium undulatum and from Kyrtuhrix maculans.     

5-(艹孟)氧基-3,4-二取代丁烯内酯NMR的研究

报道了光学纯5-(1-(艹孟)氧基)-3,4-二取代-2(5H)-呋喃酮的¹H NMR和¹³C NMR数据,研究了不同取代基对结构以及核磁参数的影响.     

Asymmetric synthesis of (3S) 3-benzoyloxymethylisobenzofuranone and its 3R enantiomer as analogues of α,β-butenolides

Both enantiomers of 3-benzoyloxymethylisobenzofuranone have been obtained in good yield in six steps from phthalaldehyde using a d-xylose derivative as a chiral protecting group. The two chiral heterocycles are γ-hydroxymethyl-α,β-butenolide analogues having a benzene ring in positions 2 and 3. The key step was the dihydroxylation using both OsO₄ and AD-mix developed by Sharpless. The asymmetric dihydroxylation using AD-mix required a double diastereoselectivity and gave excellent diastereoisomeric excess.     

Efficient synthesis of functionalized spiro-2,5-dihydro-1,2-λ-oxaphospholes

The reaction of ethyl propiolate with triphenylphosphine (Ph₃P) in the presence of N-alkylisatins led to ethyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ⁵-oxaphosphole-4-carboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones in good yield. The reaction of dialkyl acetylenedicarboxylates with Ph₃P in the presence of N-alkylisatins led to dialkyl 2,2,2-triphenyl-2,5-dihydro-1,2-λ⁵-oxaphosphole-3,4-dicarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones and alkyl 4-(alkoxy)-5-oxo-2,5-dihydro-3-furancarboxylate-spiro-1-alkyl-1,3-dihydro-2H-indol-2-ones.