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Ozonolytic cleavage

The ozonolytic cleavage of cycloalkenes in the presence of methanol produces a chain with an aldehyde and a methoxy hydroperoxide group at the termini.8 The unsymmetrical ozonolysis product is manipulated in several... [Pg.155]

Either photocatalysis or ozonation alone achieved rapid disappearance of aromatic pesticide. In contrast, mineralization (TOC removal) was slow for both. However, photocatalytic mineralization was enhanced considerably by ozone pretreatment (Fig. 9.16).31) This effect may be explained by ozonolytic cleavage of the aromatic ring and subsequent formation of aliphatic compounds which are more degradable by photocatalysis. Simultaneous use of photocatalyst and ozonation (illuminated by 254 nm light) showed synergetic effect on TOC removal (Fig. 9.17).32) In this process scavenging of electrons by ozone is considered to play the most important role. [Pg.271]

Carreira has reported that the aldol addition reaction to fiiran 2-carboxaldehyde may be performed on preparative scale (0.5 mol) with as little as 0.5 mol % catalyst (Scheme 8B2.12) [30], The adduct is isolated as a crystalline solid with 94% ee a single recrystallization allows access to 122 with >99% ee. Ozonolytic cleavage of the furan unmasks a carboxyl function, providing acid 124. This acid has been used in a convergent synthesis of the amphotericin C ]-C3 polyol portion. Moreover, 124 has been utilized in the synthesis of a number of pharmacologically important structures such as HMG CoA reductase inhibitors for the treatment of hypercholesterolemia [34],... [Pg.536]

Another source of potential antimalarial compounds has been the isolation of stable ozonides 67, produced via the ozonolytic cleavage of the bicyclic ketones 68 (Scheme 11.19).66 Variation of the groups R within 68 allows for formation of a wide range of stable ozonides 67 as exemplified by R = n-heptyl that has a melting point of 75°C to 76°C. The ozonolysis can be carried out in dichloromethane at -5°C to 0°C, and the ozonides 67 usually crystallize directly from the reaction mixture. [Pg.177]

Another example of ozonolysis being used in the production of penem-type antibiotics, which are regarded as a hybrid between penicillins and cephalosporins, has been demonstrated by Osborne and colleagues82 who describe the convenient and chiral synthesis of the triazolymethylene penem 85, from 6-aminopenicillanic acid (6-APA) (86), an inexpensive and readily available chiral synthon. The multi-step synthesis incorporates a key synthetic step involving the ozonolytic cleavage of a double bond in 87 to produce an amide 88 (Scheme 11.23). [Pg.180]

The ozonolytic cleavage of the double bond leads to the formation ofhydroperoxide and aldehyde species, which are subsequently reduced to the alcohol [50]. Semibatch... [Pg.247]

Other papers related to p-menthanes concern vinylaziridine formation from pulegone oxime and from carvone-NN-dimethylhydrazone methiodate,234 non-ozonolytic cleavage of 10-trichloromethyl-limonene,235 and the stereochemistry of 1-chloro-l-nitroso-p-menthanes236 and of dihydropinol rearrangements (cf. Vol. 2, p. 34).237... [Pg.31]

Carbon-carbon double bonds in oxabicydic systems are cleaved by ozonolysis. Moreover, tri-substituted olefins generate cyclic ethers bearing side chains with differentiated ends upon ozonolytic cleavage, thus allowing subsequent selective elaboration of each appendage. Naked sugars were used extensively by Vogel as furanosides and C-nucleoside derivatives [11a]. [Pg.39]

A key step in the recent synthesis of (+)-lauthisan by Cha was the ozonolytic cleavage of the olefinic bond of the tricyclic substrate 127 to afford the cyclic ether 128, Eq. 91 [115]. A series of transformations including an enzymatic desymmetrization completed the total synthesis. [Pg.39]

In Banwell s de novo synthesis of Neu5Ac [136] cis-1,2-dihydrocatechol 228, a product of microbial oxidation of chlorobenzene, has been converted into a protected form of Neu5Ac via a fifteen steps reaction sequence (Scheme 50). Synthesis started from azido alcohol 229, obtained from catechol 228 by an established procedure [137]. This was subjected to ozonolytic cleavage and a reductive work-up to afford diol 230. Protection-deprotection reaction sequence led to alcohol 232 which was then oxidized to D-mannosamine derivative 233 using the Swem protocol. Condensation with the organozinc reagent derived from... [Pg.462]

Similar protocol was applied in the first total synthesis of KDN from non-carbohydrate sources [138]. Catechol derivative 228 was transformed into protected tetraol 235, according to the literature method [139] (Scheme 51). This, in turn, underwent smooth ozonolytic cleavage to give after reductive work-up the ester alcohol, which was converted, over three steps, into the unstable D-mannose derivative 236. Reaction of compound 236 with pyruvate anion equivalent gave a syn product 237, accompanied by the another isomer (3 2). Conversion into KDN was performed in two steps involving ozonolytic cleavage of the double bond, then deprotection with concomitant cyclization using TFA-water mixture. [Pg.463]

While conceptually simple, this approach appeared flawed when ozonolytic cleavage of the % bond in the model substrate 129 failed miserably [46]. Fortunately, ruthenium tetraoxide, generated in situ from excess sodium periodate and 10 mol % ruthenium dioxide, worked splendidly [47]. After 10 minutes the reaction was complete, and the dione 130 was isolated in an 80% yield. [Pg.230]

To test the proposed route we capitalized upon our ability to use the intramolecular diyl trapping reaction to synthesize 95, the mono-ketal analog of 143. Ozonolytic cleavage of the C-C n bond of 95 followed by reduction with NaBIfy afforded diol 145 in an 85% yield. The primary alcohol was selectively protected as a silyl ether, and the secondary alcohol oxidized with PCC to provide ketone 146 as a 1 1 mixture of diastereomers. [Pg.236]


See other pages where Ozonolytic cleavage is mentioned: [Pg.113]    [Pg.204]    [Pg.616]    [Pg.764]    [Pg.162]    [Pg.1044]    [Pg.295]    [Pg.292]    [Pg.108]    [Pg.62]    [Pg.122]    [Pg.292]    [Pg.190]    [Pg.176]    [Pg.590]    [Pg.58]    [Pg.154]    [Pg.287]    [Pg.292]    [Pg.285]    [Pg.401]    [Pg.401]    [Pg.57]    [Pg.154]    [Pg.524]    [Pg.840]    [Pg.524]    [Pg.167]    [Pg.291]    [Pg.35]    [Pg.45]    [Pg.226]   
See also in sourсe #XX -- [ Pg.167 , Pg.291 ]

See also in sourсe #XX -- [ Pg.13 , Pg.258 , Pg.604 ]

See also in sourсe #XX -- [ Pg.226 , Pg.230 , Pg.236 ]

See also in sourсe #XX -- [ Pg.13 , Pg.258 , Pg.604 ]

See also in sourсe #XX -- [ Pg.188 ]




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