Ozonolysis, reductive

Conceptually closely related, cefroxadi ne (40) can be prepared by several routes, including one in which the enol (33) is imethylated with diazomethane as a key step. A rather more involved route starts with comparatively readily available phenoxymethylpenicillin sulfoxide benzhydryl ester (36). This undergoes fragmentation when treated with benzothiazole-2-thiol to give Ozonolysis (reductive work-up) cleaves the... 

Low -molecular-weight ozonides are explosive and are theretore not isolated. Instead, the ozonide is immediately treated with a reducing agent such as zinc metal in acetic acid to convert it to carbonyl compounds. The net result of the ozonolysis/reduction sequence is that the C=C bond is cleaved and oxygen becomes doubly bonded to each of the original alkene carbons. If an alkene with a letrasubstituted double bond is ozonized, two ketone fragments result if an alkene with a trisubstituted double bond is ozonized, one ketone and one aldehyde result and so on. 

The structure and carbon chain distribution of sodium vinylidenesulfonate (VOS) has been investigated by Hashimoto et al. [119] using NMR, IR, and chromatographic techniques. The double-bond distribution of VOS was determined using ozonolysis-reduction-GLC. The position of the sulfonic acid groups... 

Hoye and Richardson have published an ingeneous synthesis of the tricyclic iridoid sarracenin (170) which relied on the Paterno-Buchi cycloaddition between acetaldehyde and cyclopentadiene as the intial step (Scheme 38)79. This reaction provided a 5 1 mixture of adducts 166a and 166b. The major adduct was opened with camphor-10-sulfonic acid (CSA) in methanol and the alcohol was tosylated to give 167. Displacement with malonate 168 and decarboalkoxylation/demethylation steps gave 169. Ozonolysis, reductive workup and acid-catalyzed acetalization then furnished 170. 

The syntheses of (-l-)-mww,a ri,m -dicyclohexano-18-crown-6, i+)-trans-cyclohexano-15-crown-5, and (-l-)-r wis-cyclohexano-18-crown-6 (115) ftom (-l-)-mi/w-cyclohexane-l,2-diol (Figure 15) have been described. They involve base-promoted cyclizations with the appropriate ditosylates after chain extension of the chiral diol using the allylation-ozonolysis-reduction procedure. 

The Staudinger [2+2] cycloaddition of chiral carbohydrate Schiff base with phthalimidoacetyl chloride has yielded the sugar-based monocyclic (3-lactam as a single isomer [88]. This latter could be transformed in several (3-lactams variously functionalized through ozonolysis, reduction, hydrolysis, and acetylation reactions, (Scheme 26). 

The four related compounds oxalomycin (157), neooxalomycin (158), cur-romycin A (159), and curromycin B (160) were reported in 1985 157 and 158 were isolated from a yet to be identified Streptomyces species (79, 80) and 159 and 160 from an ethidium bromide-treated strain of S. hygroscopicus (81, 82). The absolute configuration of oxalomycin (157) and neooxalomycin (158) has been determined by application of a combination of X-ray crystallography and chemical correlation to degradation products, the important derivatives being the p-bromobenzoate 161, obtained from 157 by ozonolysis-reduction, acetylation, partial hydrolysis, and reacylation with p-bromobenzoyl chloride, and the erythro acetate 162 which was obtained along with the threo compound 163 after acetylation of the ozonolysis products of 157 (79, 80). No stereochemical infor-... 

One of the most common uses of ozonolysis has been for determining the positions of double bonds in alkenes. For example, if we were uncertain of the position of the methyl group in a methylcyclopentene, the products of ozonolysis-reduction would confirm the structure of the original alkene. 

Ozonolysis-reduction of an unknown alkene gives an equimolar mixture of cyclohexane-carbaldehyde and butan-2-one. Determine the stmcture of the original alkene. 

Give structures of the alkenes that would give the following products upon ozonolysis-reduction, (a) O O... 

Both permanganate and ozonolysis break the carbon-carbon double bond and replace it with carbonyl (C=0) groups. In the permanganate cleavage, any aldehyde products are further oxidized to carboxylic acids. In the ozonolysis-reduction procedure, the aldehyde products are generated in the dimethyl sulfide reduction step (and not in the presence of ozone), and they are not oxidized. 

The cleavage of a carbon-carbon bond through oxidation. Carbon-carbon double bonds are commonly cleaved by ozonolysis/reduction or by warm, concentrated permanganate, (p. 366) The addition of aqueous mercuric acetate to an alkene. (p. 340)... 

Diols (glycols), such as those formed by dihydroxylation of alkenes, are cleaved by periodic acid (HI04). The products are the same ketones and aldehydes that would be formed by ozonolysis-reduction of the alkene. Dihydroxylation followed by periodic acid cleavage serves as a useful alternative to ozonolysis, and the periodate cleavage by itself is useful for determining the structures of sugars (Chapter 23). 

The relative stereochemistry of the substituents attached to the cyclopropane ring of presqualene alcohol received further confirmation by a synthesis of the triacetate (13), obtainable from (1) by ozonolysis, reduction, and acetylation. Treatment of 3-methyl-truns-hex-2-ene-l,6-diacetate (14) with ethyl diazoacetate in the presence of copper powder gave two isomers (15) and (16) whose stereochemistry was assigned by n.m.r. The triacetate derived from synthetic (15) by reduction and acetylation was identical in all respects with the triacetate (13) from natural presqualene alcohol. Presqualene alcohol has a c.d. curve similar to, but of opposite sign to, that of (li ,2i )-trans-chrysanthemyl alcohol (17). The mechanism for the stereospecific biosynthesis of squalene from farnesol via presqualene alcohol has received detailed comment. ... 

Asymmetric crotylboration and subsequent methylation furnishes 1105 with >20 1 dia-stereoselectivity. Introduction of the protected terminal hydroxyl group is accomplished by ozonolysis, reductive work-up, and j 7-methoxybenzylation. The epoxide is formed by intramolecular cyclization of the deprotected primary alcohol with the mesylated secondary alcohol. 

Fig. (14). The diol (137) was converted to the ketone (157) by the standard organic reactions. Photoaddition of allene to (157) affords the methylene cyclobutene (158) which is converted to the aldol (162) by ketalization, ozonolysis, reduction and hydrolysis respectively. The derivative (164) prepared from (162) undergoes a chugaev reaction affording the alcohol (165) whose mesyl derivative (166) suffered rearrangement furnishing the allylic alcohol (167) which is converted to the ketone (168). Itis subjected tl lithium ammonia reduction to obtain (169) wich can be converted to aphidicolin (148) by reaction already desccribed.

With respect to polymer synthesis and to the development of biologically active compounds in recent years, the ozonolysis/reductive cleavage of OA or MO or the fragmentation of the intermediary carbonyl oxide to 9-oxononanoic acid and its respective methyl ester gained attention again [33-39]. 9-Oxononanoic acid can be easily converted to 9-amino- or 9-hydroxynonanoic acid as sources for polyamides and polyesters [40]. A French patent claimed the synthesis of oxo-nonanoic acid via homometathesis of OA, followed by reductive ozonolysis of the unsaturated C18 diacid obtained [41]. 

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