Synthetic routes to the piperolides, fadyenolides, epoxypiperolides, and related compounds

Abstract

Syntheses of the piperolides, the fadyenolides, epoxypiperolide, and related compounds are described.( f ) -Narthogenin is also efficiently produced.From the Mexican plant Piper sanctum' we have previously isolated and characterised piperolide (l),' methylenedioxypiperolide (2),' ( + )-(7S,SS)-epoxypiperolide (3),'-" (-)-erythro-7,8-dihydro-7,8-dihydroxypiperolide (4),5 as well as a possible photoisomerisation product (5E)-piperolide (5),6*7 From Piper fudyenolii, indigenous to Jamaica, we have isolated and characterised similar butenolides, the fadyenolides (6) and (7).'These compounds are of particular interest for two reasons.First they are unique tetronates (derivatives of 4-hydroxybut-3-enolides) derived from higher plants rather than from fungal, microbial, or marine source^.^*^-'^ Secondly some of them, as well as certain of our synthetic products, have strong sedative as well as other most interesting physiological properties.It is tempting to speculate on a New World mutation in Piper species that leads from the usual pyrone derivatives such as kawain (8a)14 and methysticin (8b)14 produced by * We thank Dr. R. Pardasani for these experiments.

A Rapid Entry to Diverse γ‐Ylidenetetronate Derivatives through Regioselective ­Bromination of Tetronic Acid Derived γ‐Lactones and Metal‐Catalyzed Postfunctionalization

“…The aldol adducts were converted directly into γ‐lactones 42 – 64 by a two‐step/one‐pot sequence that proceeded through an esterification with trifluoroacetic anhydride and an elimination reaction with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as the base5b,5c in dichloromethane. Compounds 42 ,1i,1j 43 ,3a and 51 1i are known compounds or have been previously reported in the literature. Compounds 42 , 44 , 47 – 54 , 56 , 58 , 60 , 61 , 63 , and 64 were obtained as the ( Z ) stereoisomer (in our preliminary communication,4 the ( Z ) stereochemistry of ferrocenyl derivative 50 was confirmed by single‐crystal X‐ray diffraction analysis).…”

“…The first approach (method A) to prepare γ‐ylidenetetronates I follows literature procedures that were developed for analogues of I 1j,5b,5c. Tetronates 1a – 1d were treated with n BuLi (1.1 equiv.)…”

Calixpyrrole Derivatives: “Multi Hydrogen Bond” Catalysts for γ-Butenolide Synthesis

“…The products of this versatile carbon-carbon bond forming reaction are butenolide-like compounds which represent a substructure of a more complex assembly found in numerous biologically important natural and synthetic products [ 20 , 21 , 22 , 23 ]. The diastereoselective addition of variously substituted furan-based silyloxydiene synthons to a variety of achiral aldehydes and acetals using Lewis acids as catalysts has been reported in a number of papers [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. MacMillan described the first enantioselective organocatalytic 1,4-addition of TMSOF to unsaturated aldehydes with high enantioselectivities [ 31 ].…”

Concise Synthesis of Key 3-Polyenoyl-5-methylenefuran-2,4-dione Putative Intermediates in Quartromicin Biosynthesis

“…14 Thus 5-[(dimethylamino)methylene]-4-methoxy-5H-furan-2-one (19) was prepared from commercially available 4-methoxy-5H-furan-2-one and dimethoxymethyl dimethyl amine according to the procedure of Pelter et al 15 and converted directly into 18 by reaction with five equivalents of sodium triacetoxyborohydride and acetic acid in refluxing dichloroethane (Scheme 3).…”