Bayer-Villiger oxidations

Finally, we mention here recent progress made in the Bayer-Villiger oxidation. Zeolite Sn-Beta (1.6 wt.% Sn) was found to be an excellent catalyst [25], Thus, the monoterpene dihydrocarvone gives - with Sn-Beta and H202 - exclusively the lactone (Scheme 5.7), whereas m-chloroperbenzoic acid and Ti-Beta/H202 give the epoxide as the main product. 

In the past few years, new approaches for the enantioselective synthesis of / -benzyl-y-butyrolactones appeared in the literature. Some of these approaches involve the asymmetric hydrogenation of 2-benzyl-2-butenediols (j [34]), the radical mediated rearrangement of chiral cyclopropanes (r [35]), the transition metal catalyzed asymmetric Bayer-Villiger oxidation of cyclobutanones n [36]), or the enzymatic resolution of racemic succinates (g [37]). 

The key step in the biosynthesis of brassinosteroids is the conversion of castasterone to brassinolide. This reaction is a lactonization of the steroidal B-ring or a Bayer-Villiger-oxidation. Tomato cell suspension cultures have been extensively studied in respect to the metabolism of 24-< / i-castasterone and 24-ep/-brassinolide [21, 22, 32, 33]. A microsomal fraction of tomato cell cultures, induced by 24-epi-castasterone, was able to convert this substrate into 24-epi-brassinolide (Fig. (11)). The specific enzyme activity was determined to be 230 fkat/mg protein with NADPH serving as the only accepted electrondonor [24],... 

The chemical properties of cyclic ketones also vary with ring size. Lower members (addition reactions, than corresponding acyclic ketones. The Cg—C12 ketones are unreactive, reflecting the strain and high enol content of medium-sized ring systems. Lactones are prepared from cyclic ketones by the Bayer-Villiger oxidation reaction with peracids. S-Caprolactone is manufactured from cyclohexane by this process ... 

The two oxidoreductase systems most frequendy used for preparation of chiral synthons include bakers yeast and horse liver alcohol dehydrogenase (HLAD). The use of baker s yeast has been recendy reviewed in great detail (6,163) and therefore will not be covered here. The emphasis here is on dehydrogenase-catalyzed oxidation and reduction of alcohols, ketones, and keto acid, oxidations at unsaturated carbon, and Bayer-Villiger oxidations. 

Bayer-Villiger oxidation of the Ferrier carbocyclization products 69 and 70, derived from D-glucose, gave the isomeric 5-deoxyhexofuranosiduronic... 

G. R. Krow, The Bayer-Villiger Oxidation of Ketones and Aldehydes, Org. React. 1993, 43, 251-798. 

Fig (9) Methyl dihydroabietate (64b) has been converted to compound (68). The standard organic reactions have been utilized for its conversion to nitrite (72) which on irradiation followed by oxidation yields lactone (74). Cleavage of lactone ring followed by hydrogenation and esterification produced (76) which was converted to (77) by Friedel-Crafts acylation and Bayer-Villiger oxidation. This yields psiferic acid (1) tty hydrolysis. 

Arvai, G, Fattori, D, Vogel, P, Substituent effects on the regioselectivity of the Bayer-Villiger oxidation of 7-oxabicyclo[2.2.1]heptan-2-ones, Tetrahedron, A i, 10621-10636, 1992. 

Bayer-Villiger oxidation. The oxidation of 3-methoxy-16/3-acetyl-D-nor-l,3,5(10)-estratriene (1) to the acetate (2) presented difficulties the usual per-... 

Oxidation of aldo- or keto-phenols to polyphenols by H202 (a Bayer-Villiger oxidation) (see 1st edition). 

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