Butenolides hydroxy

The reaction of vinyloxiranes with malonate proceeds regio- and stereose-lectively. The reaction has been utilized for the introduction of a 15-hydroxy group in a steroid related to oogoniol (265)(156]. The oxirane 264 is the J-form and the attack of Pd(0) takes place from the o-side by inversion. Then the nucleophile comes from the /i-side. Thus overall reaction is sT -StM2 type, in the intramolecular reaction, the stereochemical information is transmitted to the newly formed stereogenic center. Thus the formation of the six-membered ring lactone 267 from 266 proceeded with overall retention of the stereochemistry, and was employed to control the stereochemistry of C-15 in the prostaglandin 268[157]. The method has also been employed to create the butenolide... 

Butenolide, 2-hydroxy — see Isotetronic acids Butenolide, 3-hydroxy — see Tetronic acids But-2-enolide, 4-alkylidene-synthesis, 4, 697 Butenolides H NMR, 4, 578 mass spectrometry, 4, 585 structure, 4, 551 synthesis, 1, 416 trimethylsilylation... 

Diastereoselective aldol condensations. This furan (1) can undergo condensation with aldehydes as a butenolide to form 8-hydroxy-a,(3-unsaturated--y-lactones (2). The diastereoselectivity can be controlled by the choice of catalyst. Lewis... 

A stereoselective osmylation approach was applied to the synthesis of C(l)—C(7) and C(7)—C(13) subunits of erythronolide A41. A key synthon of the erythronolide A seco acid, 30, was prepared in an enantiomerically pure form by utilizing a stereoselective osmylation of the chiral hydroxy (Z, )-diene ester 31 and subsequent hydrogenation of the resulting butenolide 32 (equation 24). 

ButenoUdes. 4-Substituted 2-butenoIides can be prepared by reaction of organolithium reagents with 4-hydroxy-2-butenolide (1), easily prepared from furfural (equation I). The reaction of 1 with 2 equivalents of RLi or ArLi in-THF at... 

PCC will oxidize 2-hydroxymethyl-5-bromofuran derivatives (90) to -y-hydroxy-butenolides (91) (79TL1507). This simple, high yield procedure thus provides an important route to these synthetically useful intermediates (equation 2). 

Photosensitized oxidation offurans.3 The endoperoxide (2) formed in photosensitized (methylene blue) oxidation of 3-substituted or 3,4-disubstituted furans in acetone at -40° rearranges at 20° to 4-hydroxy-2-butenolides in 30-97% yield. Example ... 

OLyfi-Butenolides.1 Reaction of (E)-y-hydroxy-a, (3-unsaturated esters with thiophenol results in cyclization to 3-phenylthiobutyrolactones, which can be converted into 3-phenylthiobutenolides or butenolides. 

If the halide and the hydroxy group are present in the same molecule, reaction (107) leads to the synthesis of lactones.484 With complex (102) as catalyst a series of butenolides were prepared in good yields from vinyl iodides (equation 110). Four- and six-membered ring lactones and a-methylene lactones were prepared. 5,486 The mechanism proposed was analogous to that of Scheme 37. This cyclization has been used in the synthesis of the natural product zearalenone.487 PdCl2 was the catalyst. 

Thus, 1.7-octadiene (79), which was subjected to monohydroboration followed by asymmetric dihydroxylation of the remaining double bond to give triol 80 with approximately 80% ee. Further transformations then afforded the desired butenolide 81. Double asymmetric dihydroxylation of diene 83 and subsequent protection gave hydroxy lactone 84 [98], which was then converted into acetylenic bis(hydroxy)bistetrahydrofuran 82 as the required intermediate for the (+)-asimicin synthesis. Mitsunobu inversion at C-24 gave rise to the diastereomeric (+)-bullatacin precursor. 

Butenolides. The fmnal steps in a synthesis of jolkinolide E (4) involve formation of the butenolide ring by reaction of the a-hydroxy ketone 1 with the mixed anhydride of trichloroacetic acid amd a-(diethylphosphono)propionic acid (2) with catalysis by DMAP. The ester 3 undergoes an intramolecular Wittig-Horner reaction in the presence of NaH to give 4. ... 

Butenolides. 21-Hydroxy-20-keto steroids react with 1 to form cardenolides by an intramolecular Wittig reaction (equation I).2... 

The above-described problem demonstrates the first enantioselective synthesis of dysidiolide, a C25 isoprenoid antimitotic agent. The central transformations are the sulfenylation-dehydrosulfenylation sequence to prepare an a,/5-tnone, the biomimetic cationic 1,2-rearrangement to form stereoselectively the bicyclic scaffold, vinyl cuprate displacement of an iodide furnishing the C-l side chain and the photochemical oxidation of furan to generate the j hydroxy-butenolide functionality. 

For example, N-(2-hydroxyphenyl)imines 9 (R = alkyl, aryl) together with chiral zirconium catalysts generated in situ from binaphthol derived ligands were used for the asymmetric synthesis of a-amino nitriles [17], the diastereo- and/or enantioselective synthesis of homoallylic amines [18], the enantioselective synthesis of simple //-amino acid derivatives [19], the diastereo- and enantioselective preparation of a-hydroxy-//-amino acid derivatives [20] or aminoalkyl butenolides (aminoalkylation of triisopropylsilyloxyfurans, a vinylogous variant of the Mannich reaction) [21]. A good example for the potential of the general approach is the diastereo- and enantioselective synthesis of (2R,3S)-3-phenylisoserine hydrochloride (10)... 

Patil, S.N., Stephens, B.E. and Liu, F. (2008) A tandem Baylis-Hillman-singlet oxygen oxidation reaction for facile synthesis of "/-substituted y-hydroxy-butenolides. Tetrahedron, 64 (48), 10831-10836. 

Hydroxymethylation of ketone (155) was followed by protection of the aliphatic hydroxy group (2-methoxypropyl ether) and addition of an a-benzyloxymethylene group at C-4. Acidic workup at the last stage of the reaction sequence produced (156). Its transformation to aldehyde (157) was carried out by successive treatment with methoxypropyl ether, acetic anhydride and pyridine, hydrochloric acid and methanol, and finally chromic acid, pyridine and hydrochloric acid. Dehydration of (157) led to the formation of (158) in 20% yield. Reagents other than the mentioned produced appreciable quantities of the cis A/B isomer. The butenolide (159) was finally synthesized by oxidation and hydrogenolysis. In order to complete the synthesis of triptolide it was necessary to introduce the... 

Ried and Bodenstedt345 obtained an interesting a,)S-unsaturated butenolide, when the diazofuran (60) was warmed with water. It is possible that the a-hydroxy derivative forms first, which then dimerizes at the -position in its keto form. The reaction might proceed by a radical mechanism. 

The structure of the epoxy-dialdehyde (15), from Afromomum daniellii (Zingiberaceae), was established by correlation with c -12-norambreinolide. The hydroxy-acid (16), salvic acid from Eupatorium salvia,and the ring B seco-labdane jhanic acid (17) from Eupatorium jhanii are two further diterpenoids from these species of the Compositae. The structure of the latter rests on interpretation of the H and C n.m.r. data. Gutierrezia lucida (Compositae) contains the 13-epimeric acids (18) related to agathic acid together with the butenolide (19). Some esters of 6-hydroxylabdane-17-carboxylic acids were detected in G. mandonii. The investigation of Cistus species has continued. The ent-labdane acetyl-laurifolic acid (20) is a component of Cistus laurifolius ... 

Acylation of alkenes and alkynes. Dienes and alkynes can be acylated under phase-transfer conditions by carbon monoxide and methyl iodide in the presence of -catalytic amounts of Co2(CO)s. The reaction with alkynes results in a 4-hydroxy-2-butenolide the probable mechanism is shown in equation (I). 

Synthesis of P-Keto Sulfoxides. Optically active p-keto sulfoxides are very useful building blocks (eq 4) because they can be stereoselectively reduced to afford either diastereomer of the corresponding p-hydroxy sulfoxide under appropriate conditions (Diisobutylaluminum Hydride or Zinc ChloridefDlBALf and thus give access to a wide variety of compounds chiral carbinols by desulfurization with Raney Nickel or LithiumJethyhmme ini the case of allylic alcohols epoxides via cyclization of the derived sulfonium salt butenolides by alkylation of the hydroxy sulfoxide 1,2-diols via a Pummerer rearrangement followed by reduction of the intermediate. ... 

The condensation of the dilithio derivative of (R)-(+)-3-(p-tolylsulfinyl)propionic acid with protected glycoaldehy-des (O-r-butyl and 0-benzyl) gives 5-alkoxy-4-hydroxy-3-(p-tolylsulfinyl)pentanoic acids, which spontaneously cyclize to the corresponding 3-sulfinyl-4-alkoxymethyl butanolides (eq 4). Pure diastereomers can be separated by flash chromatography and are obtained in comparable amounts. The corresponding optically pure butenolides are obtained by pyrolytic elimination of the sulfoxides and then transformed into natural (-i-)-(/ )-umbelactone (eq5). 

---