Baeyer-Villiger type

Levitt MS, RE Newton, SM Roberts, AJ Willetts (1990) Preparation of optically active 6 -fluorocarbocyclic nucleosides utilising an enantiospecific enzyme-catalysed Baeyer-Villiger type oxidation. J Chem Soc Chem Comm 619-620. 

The pseudobenzylisoquinoline alkaloids are fairly widespread in nature, being found among members of Berberidaceae, Annonaceae, Fumariaceae, and Ranunculaceae. The biogenesis of the pseudobenzylisoquinoline alkaloids assumes their formation from protoberberinium salts by C-8—C-8a bond scission in a Baeyer-Villiger-type oxidative rearrangement to produce the enamides of type 73 and 74. These amides may be further biotransformed either to rugosinone (76) type alkaloids by hydrolytic N-deformylation followed by oxidation or to ledecorine (75) by enzymatic reduction. These transformations were corroborated by in vitro studies (80-82). It is suggested that enamide seco alkaloids may be precursors of aporphine alkaloids (80), on one hand, and of cularine alkaloids (77), on the other. 

It was postulated (169) that these amides are 8,8a-secobenzophenanthridine alkaloids produced by oxidative cleavage of ring B of the corresponding benzophenanthridines. The success of Baeyer-Villiger-type oxidations of the immonium bond of benzophenanthridine skeletons (168,171,172,175) indicates that this type of oxidation could be a real biological pathway. 

Optically Active Lactones from Metal-Catalyzed Baeyer-Villiger-Type Oxidations Using Molecular Oxygen as the Oxidant... 

Alphand, V., Archelas, A. andFurstoss, R., Microbial transformations 16. One-step synthesis of a pivotal prostaglandin chiral synthon via a highly enantioselective microbiological Baeyer-Villiger-type reaction. Tetrahedron Lett., 1989, 30, 3663. 

The intermediate dioxetane 36 is probably formed via ring opening and subsequent Baeyer-Villiger-type oxidation [2]. 

A Baeyer-Villiger type oxidation of ketonic substrates occurs exclusively at the carbonyl function under aprotic conditions by use of BTSP and a catalytic amount of McsSiOsCCFs (MesSiOTf) (equation 28). C—C bonds are not affected (Table 5). ... 

This homologous Baeyer-Villiger type oxidative ring expansion represents a conceptually new protocol illustrating the substantial value of one-pot, four-component annulations as a flexible and simple new synthetic method. 

Further information is available on the biosynthesis of vinblastine-type alkaloids (cf. Vol. 11, p. 19 Vol. 10, p. 19). Anhydrovinblastine (61) was found to be metabolized to leurosine (63) and Catharine (64) in cultures of a C. roseus cell-line that do not normally produce these alkaloids.55 Ring-opening in the conversion of the skeleton of anhydrovinblastine (61) into that of Catharine (64) has been suggested to occur by Baeyer-Villiger-type oxidation of an imine las (62). The alternative 21 -imine could give catharinine.56... 

Ans. Carbonium ion (Baeyer-Villiger type) and Beckmann rearrangements. 

Cyclic ketones may be converted to cyclic ethers via the oxidation of the corresponding diethyl ketal using MCPBA.257 This reaction is formally a double Baeyer-Villiger type oxidation followed by elimination of diethylcarbonate (Figure 3.58). 

A final oxidation type that has been observed is the catalysis of Baeyer-Villiger-type oxidations of cyclic ketones to lactones.53 Understandably, the strained cyclobutanone is the best substrate, giving 80% conversion after 24 h at 25°C (tert-butanol solvent). Larger ring ketones proceed more slowly, although selectivity remains high. Elevated temperatures increase the rate without sacrificing selectivity cyclopentanone is converted to the lactone in 72% yield after 1 h at 70°C in THF. Complex 4 was presumed to be the active species. 

When the norditerpenoid alkaloid imine 360 was subjection to reaction with MeI-NH40H and MCPBA, oxaziridine 361 was formed in 50% overall yield <2002H(57)2357>. Key steps in the proposed mechanism for the formation of 361 involve formation of a quaternary ammonium salt with Mel and peracid oxidation through a Baeyer-Villiger-type process. 

Several types of flavoprotein monooxygenases exist. One group catalyzes electrophilic aromatic substitution or heteroatom oxidation reactions, whereas the other group catalyzes Baeyer-Villiger-type oxidations of ketones (Fig. 2) (13, 17). 

In the second study, the above one-step mechanism was discounted and a two-step mechanism (a Baeyer-Villiger type) was advanced. Although the rates are summarized as r" =/fobs [C= N] [perbenzoic acid], the reaction exhibits complex kinetics because of the two adverse effects, acceleration by carboxylic acids and pro tic solvents, and retardation by basic solvents including ethers and alcohols (Scheme II). 

Trost also found that treatment of these cyclobutanones with sodium methoxide and diphenyl disulfide leads to in situ bisulfenylation and ring cleavage (secosulfenylation). This was applied to the total synthesis of verrucarol, a complex tetrahydrochromanone substituted at the ring junction by a hydroxymethyl substituent. The synthetic strategy twice used the cyclobutanone formation from 1-lithiocyclo-propyl phenyl sulfide and a ketone, followed by the secosulfenylation process and Baeyer-Villiger type rearrangement of cyclobutanone. Only this part of the synthesis is described in Scheme 28. 

Work on alkaloid isolation is summarized in Table 11.3 2—396 Arnottianamide (145 R = H, R = Me) and isoarnottianamide (145 R = Me, R = H) have been isolated as minor constituents of Zanthoxylum cuspidatum. These amides can be obtained chemically by Baeyer-Villiger-type oxidation of the immonium group in chelery-thrine and nitidine respectively and a similar biogenesis is suggested. Three Argemone subfusiformis taxa and A, polyanthemos contained mainly the same... 

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