Methyl retinoate oxidation

Base-promoted desulphonylation of this compound provides methyl retinoate (19) (aIl- 13Z=5 l). The Cio-sulphone 28 also works as a coupling partner of 25 (Scheme 9) [11]. The Cio-disulphone 29 thus obtained is converted into 30 by successive oxidation, Pummerer reaction, NaBH4-reduction, Jones oxidation and methylation with diazomethane. Treatment of 30 with NaOMe in MeOH furnishes methyl retinoate (18) (all- 13Z=6 4). 

The direct oxidation of methyl retinoate (43) with manganese(IV) oxide to give methyl 4-oxoretinoate (317) has been described (Rao eta/., 1972 Henbest, 1957 Barua and Ghosh, 1972 Sokolova et al., 1980). In this manner, retinoids... 

Oxidation of methyl retinoate (43) with manganese(IV) oxide gave the 4-keto ester (317), which was converted to the acid (188), and to the 4-hydroxy ester (318). The latter compound has also been employed as an intermediate in the synthesis of 3,4-didehydro compounds (Henbest, 1957 Rao et aL, 1972 Barua and Ghosh, 1972). 

Two other metabolites (199) and (203) of (all-/ran5 )-retinoic acid (3) (Hanni et al., 1976 Hanni and Bigler, 1977) posses an oxidized methyl group in the ring. The carbon skeleton of (199) was built on the basis of a method that was successfully used for the synthesis of the trisporic acids, which have a similar structure (Yakovleva et al., 1978 Prisbylla et aL, 1979). 

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). 

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-... 

The carbon skeleton of the naphthalene compounds (563) and (564), which are structurally analogous to ethyl retinoate (24) and retinaldehyde (2), was obtained via the ketone (562) (Akhtar et al., 1982). The aldehyde (564), which binds, as the chromophore, to opsin, was obtained by reducing the ethyl ester (563) with lithium aluminum hydride/aluminum chloride and finally oxidizing the product with manganese(IV) oxide. The trans double bond of methyl (all- )-... 

---