Methyl senecioate

Pachybasin, 2-methyl-4-hydroxyanthra-9,10-quinone has been obtained in 73% yield by Diels-Alder addition from 2-bromonaphthoquinone and the vinylketene mixed acetal, 1-trimethylsiloxy-1-methoxy-3-methylbuta-1,3-diene, by reaction in dichloromethane containing potassium carbonate, heating with sodium acetate and finally aromatisation of the crude product by refluxing in ethanol The diene was accessible from methyl senecioate (methyl 3-methylbut-2-enoate) by treatment with lithium diisopropylamide and trimethylchlorosilane (ref.25). 

The preparation of all-rran -retinoic acid labeled with carbon-14 in positions 13 and 14 has been described (Kaegi et aL, 1980) and is depicted in Fig. 4. The methyl senecioate-2,3- C was prepared from acetone-2- C and the labeled phosphonoacetate (XIV) by a Homer-Emmons reaction. The preparation of the methyl diethyl phosphonoacetate-2- C (XIV) was simplified by using a novel... 

The Matsui condensation of p-ionylideneacetaldehyde (I) and methyl senecio-ate-2,3- " C2 (XV), carried out in anhydrous ether (Manchand et al, 1965) with potassium amide, furnished a crude product in 76% yield containing dXVtrans-retinoic-13,14- " 2 acid (Vllb) and its 13-cis isomer in a ratio of about 2 1. The pure all-trans acid, with a specific activity of 51 mCi/mmol, was obtained by crystallization. 

Nucleophilic addition of ester-derived enolate to the bicyclo[3.3.0]octan-2-one system of diacetone glucos-3-ulose usually occurs at the convex jS-face of the carbonyl (as for other nucleophiles), except for senecioate-derived enolate (from 3-methyl cro-tonate) for which a-attack in diethylether solvent is in contrast to the jS-face attack in THF the reason for this anomalous behaviour is not clear. 

Most of the new source reports concern species from the Asteraceae, with many of the flavonols being isolated from aerial parts, where they are accumulated externally. They range from simple to more complex structures. There appears to be a tendency towards 6-methox-ylation rather than towards 8-methoxylation, in addition to possible OMe-substitution of other positions of the flavonol molecule. Flavonols with 6,8-di-O-methylation and additional OMe-groups are also found in several genera such as Senecio, Psiadia, or Inula, to cite but a few examples. 

In the first reports on the use of esters of 4-bromo-2-butenoic acid (191a and b, crotonic acid) and of 4-bromo-3-methyl-2-butenoic acid (191c, senecioic acid), the corresponding Reformatsky reactions with benzaldehyde were performed with the old-fashioned procedure, which required heating the haloester, the aldehyde and granulated zinc in benzene/ether mixtures at reflux temperature. 

Moving from 195 to senecioate enolate 196, the introduction of a methyl group leads to strong regiochemical effects only y-adducts are obtained at — 78 °C with 194a... 

A double ir-face selective aptotic Michael addition of the lithium dienolate, derived from the chiral senecioate (119), to cyclopentenone served for the total synthesis of (-)-kushimone (120 Scheme 45).137-138 The selectivity of the key reaction was rationalized by the assumption of a transition state as shown in (121a). A related approach involves the Michael addition of enolates, derived from chiral propionates, to methyl ( )-crotonate (Scheme 46).139 The formation of the threo isomer (122) as the major product indicates a transition state structure as shown in (121b). This method was utilized in the synthesis of the marine natural product 7,20-diisocyanoadociane (123 Scheme 47).140... 

In agreement with frontier orbital considerations, crotonic esters add to nitrones to produce p-o o esters regioselectively. This reaction provides the basis for a synthesis of the Senecio alkaloid supinidine (7). Reaction of 1 with methyl 4-hydroxycrotonate yields the isoxazolidinone 5, which is easily converted to the... 

C5H9F 4-fluoro-3-methyl-1-butene 66213-82-9 309.31 26.103 2 5216 C5H9NO senecioic acid amide 4479-75-8 444.47 38.576 2... 

E.28) (E.28) 2-Butenoic acid, 3-methyl-, 3-methylbut-2-enoic acid, 3,3-dimethylacrylic acid, senecioic acid [541-47-9] FEMA 3187... 

F.45) 2-Butenoic acid, 3-methyl-, ethyl ester, ethyl 3-methylbut-2-enoate, ethyl 3-methylcrotonate, ethyl 3,3-dimethylacrylate, ethyl isobutenoate, ethyl senecioate [638-10-81... 

Binapacryl. 3-Methyl-2-butenoic acid 2-(i-meth-ylpropyl)-4,6-dinitrophenyl ester 3-methylcrotonic acid 2-seC butyl-4,6-dinitrophenyi ester 2-sec-butyl-4,6-dinitro-phenyi 3,3-dimethylacrylate 2-sec-butyl-4,6-dinitrophenyl 3-methyl-2-butenoate 2 sec-butyl-4,6-dinilrophenyl 3-methylcrotonate 2 -see-butyl-4,6-dinitrophenyl senecioate 3,3-dimethylacrylic acid 2-sec-butyl-4,6-dinitrophenyl es. ter 4,6-dinitro-2-sec-butylphenyl P,P-dimethylacrylate 3-methyl-2-butenoic acid 2-sec-butyl-4,6-diniirophenyl ester dinoseb methacrylate senecioic aeid 2-sec-butyl-4,6-dinitrophenyl ester ENT 25793 HOE 2784 Acricid Am-box Endosan Morocide Niagara 9044. mol... 

Extraction of Senecio othonnae gave otosenine in 0.07% 3neld. The presence of one hydroxyl and one iV-methyl group was indicated by analysis. 

The nature of the acyl residues follows from the proton n.m.r. spectrum. INDOR measurements were used, wherein the methyl signals at 5 1.83,1.90, and 2.18 were chosen as monitoring lines. The methyl signal at d 1.83 is coupled with the olefinic proton at S 6.82, while the two others couple with that at 5 5.67, indicating exclusively allylic couplings. The former spin-system corresponds to the dicarboxylic acid. The chemical shifts fit mesaconic acid (5 6.69 and 5.76, respectively). The second spin-system is congruent with senecioic acid (5 1.87,... 

Butenoic acid, 3-methyl-, ethyl ester. See Ethyl senecioate... 

Citronellyl 3-methylcrotonate CAS 20770-40-5 EINECS/ELINCS 244-019-4 Synonyms Citronellyl senecioate 3,7-Dimethyl-6-octenyl trans-3-methyl-2-butenoate Properties Flash pt. (CC) > 130 C Toxicology TSCA listed Uses Fragrance in cosmetics Manuf./Distrib. Grau Aromatics http //www.grau-aromatics.de Citronellyl nitrile... 

Ethyl methyl benzene. See Ethyl toluene N-Ethyl-p-methylbenzene sulfonamide. See Ethyl toluenesulfonamide Ethyl p-methylbenzenesulfonate. SeeEthyl-p-toluenesulfonate Ethyl 4-methyl benzoate Ethyl p-methylbenzoate. See Ethyl p-toluate Ethyl 2-methyl-2-butenate. See Ethyl tiglate Ethyl 3-methyl-2-butenoate. See Ethyl senecioate... 

Aldol condensation of the retro Cj5 aldehyde (284) with ethyl senecioate (285) in the presence of potassium amide gave 4,6-retroretinoic acid (286). This compound reacted with methyl iodide to give the methyl ester, which was reduced with lithium aluminum hydride to 4,6-retroretinol (287) ( a-vitamin A ). Treatment of (287) with triphenylphosphine hydrochloride gave the C20 phos-phonium salt (288), while oxidation of (287) with manganese(IV) oxide produced the aldehyde (282) (Isler, 1971). 

The Ci5 aldehyde (4) condensed with ethyl senecioate (285) in the presence of sodium amide or lithium amide to give (13Z)-retinoic acid (17), which was converted to the methyl ester and then reduced to give (13Z)-retinol (346). Oxidation of the latter gave (13Z)-retinaldehyde (41) (Matsui et aL, 1958). 

When, however, the chain-lengthening reactions with the pure Cj5 aldehyde isomers (349) and (350) were carried out using methyl 4-diethylphosphono-senecioate ( /Z = 1.3), conventional secondary reactions gave mixtures of the aldehydes (354) and (356) and of the aldehydes (355) and (356), and these mixtures were separated by chromatography (Asato and Liu, 1975 Ramamurthy and Liu, 1975 Ramamurthy et aL, 1975 Liu and Asato, 1982). ... 

Condensation of the Cj5 aldehyde (347) with ethyl senecioate (285) in liquid ammonia or anhydrous ether in the presence of potassium amide gave (9Z)-retinoic acid (348), which was methylated in a conventional manner with diazomethane to give methyl (9Z)-retinoate (357). Reduction of (357) with lithium aluminum hydride gave (9Z)-retinol (132), which was oxidized with man-... 

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