Retinoic acid methyl ester

There have been many reports on the use of this method for the syntheses of vitamin A, methyl retinoic acid methyl ester, related derivatives, and polyenes300-310. 

Besler et al. [671] studied retinal and retinol isomer retention on a silica column (A = 325nm or 371 nm) with hexane/MlBE (97/3 and 93/7), hexane/dioxane (93/7 and 94/6), and heptane/MrBE (94/6 and 93/7) mobile phases. The purpose of this work was to find an accq)table replacement for dioxane, namely, MrBE. The best overall chromatography resulted when 94/6 hexane/dioxane resolved 11,13-di-cis-, 13-CIS-, 9,11-13-tri-cis-, 9,13-di-cis-, 11-cis-, 7,1 l-di-c , 9-cis-, 7,9-di-cis, and all-tra s retinol in 15 min. Broader peaks but better resolution were obtained for the same solute set when 93/7 hexane/MtBE was used (elution was complete in 21 min), MlBE in hexane also gave excellent resolution of 13-c/s-retinoic acid and z -trans retinoic acid methyl esters on a silica column (A = 340 nm) in <5 min, whereas dichloromethane/hexane (35/65) required 17 min and toluene/hexane (45/55) required 10 min. It was found that for the toluene/hexane mobile phase, very small changes in the water content of the system dramatically and adversely affected the chromatography. The MrBE/hexane mobile phase provided more overall stability with respect to these changes. 

E7 Retinoic acid methyl ester [339-16-2] Methyl retinoate... 

Baillet, A., Corbeau, L., Rafidson, R, and Ferrier, D., Separation of isomeric compounds by reversed-phase high-performance liquid chromatography using Ag+ complexation. Application to cis-trans fatty acid methyl esters and retinoic acid photoisomers, /. Chromatogr., 634, 251, 1993. 

Also based on the nomenclature rules for carotenoids is the use of the prefix nor for those retinoids that, compared with a standard structure, lack carbon atoms. The retinoic acid derivative (32) below is accordingly named 19,20-dinorretinoic acid methyl ester and retinoid (28) 5-acetyl-4,18-dinorretinoic acid. 

Fig. 3. Chromatogram of the methyl esters of three polar metabolites of all-tra/i5-retinoic acid Column, Partisil PXS (5 p-m) mobile phase, hexane 2-propanol (99.5 0.5), flow rate, l.l ml/min peak (1) l3-c -4-oxoretinoic acid methyl ester peak (2) all-/ra/t 4-oxoretinoic acid methyl ester peak (3) all-rranj-4-hydroxyretinoic acid methyl ester. (C. A. Frolik, unpublished results.)...

FI Etretinate [54350-48-0] (all- )-9-(4-Methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoic acid ethyl ester Ethyl 3-methoxy-2-methyl-17-nor-l,2,3,4-tetradehydroretinoate TMMP analog of retinoic acid ethyl ester... 

Base-induced elimination of sulphinate from homoallylic sulphones , from y-ketosulphones , and from 1,2-bissulphones has been used in synthetic sequences ranging from the preparation of retinoic acid and of its methyl ester , to a novel pentannulation sequence that leads to a range of cross-conjugated dienes , as exemplified by equation (69). The overall yield for the two steps was 63%. 

Several papers have described the synthesis of epoxyretinoids. The 5,6-epoxides of fmns-retinal (88) and its (9Z)-, (IIZ)-, and (13Z)-isomers were prepared by direct epoxidation of retinal with w-chloroperbenzoic acid. The 7,8-epoxides (89) of retinal, retinol, and retinoic acid and its methyl esters were synthesized from the jS-ionone epoxide (90). The exceedingly labile methyl 13,14-epoxy-13,14-dihydroretinoate (91) was made by addition of the epoxyaldehyde (92) to the phosphorane (93). Chromogen 574 , a product of the epoxidation of retinol first described in 1945, has now been identified as the... 

KNH2, large excess of methyl tiglate, NH3(1), Et20, -33°C It. (24 h) different carotenoic esters and, after subsequent reactions, acids and aldehydes e.g. torularhodin (428) and retinoic acid... 

Wittig olefination was discovered in 1953 during studies on the reactions of pentaphenyl-phosphorane, and was described in the following year as a widely suitable method for olefin synthesis [33]. As early as 1956 a patent application appeared [34], in which the synthesis of retinoic acid esters from p-ionylideneacetaldehyde and (3-alkoxycarbonyl-2-methyl)allyl-triphenylphosphonium bromide was claimed, evidence of the fact that the inventors had rapidly realized the economic potential and industrial practicability of this novel reaction [35,36]. 

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). 

A better method was available. It consisted of the reduction of retinal-11- H with lithium borohydride at ambient temperature, followed by acetylation of the obtained retinol-11- H with pyridine and acetyl chloride to give all-rran -reti-nyl-ll- H acetate in good yield (Kaegi et al., 1982a). This easily executed reduction proceeds smoothly, avoiding all the complications of the more usual reduction of the methyl ester of retinoic acid with lithium aluminum hydride at low temperature. Reduction of retinal on a 0.1-mmol scale always furnished retinyl-11- H acetate in yields better than 60% after recrystallization from methanol at low temperature. 

Dissolve retinoic acid m diethyl ether, and cool on ice. To this solution, add a slight excess (>1 1 molar ratio) of cold ethereal solution of diazomethane. Allow the solution to warm to room temperature, and evaporate the solvent under an inert gas or in a rotary evaporator. Dissolve the residue of methyl retinoate in an appro-pnate solvent. Confirm the formation of methyl retinoate by TLC (methyl retinoate migrates more rapidly than does retinoic acid) add more diazomethane if not all of the retinoic acid has reacted. Check the purity of the methyl ester by HPLC or TLC confirm purity and detemune concentration by absorbance spectrophotometry. 

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