C-8 aldehyde

SYNS ALDEHYDE C-8 C-8 ALDEHYDE FEMA No, 2797 OCTANALDEHYDE n-OCTYL ALDEHYDE... 

A series of deprotection, reduction, and reprotection steps provided a 69% yield of silyl ether 226, which was subjected to a hydroboration-oxidation sequence to afford aldehyde 267 (87%) as a mixture of isomer at C-8. Aldehyde 267 was then converted to the Emmons reagent 268 via a sequence involving addition of lithium dimethyl methylphosphonate, oxidation to the keto phosphonate, deprotection, and oxidation in 65% overall yield. 

C(7)-phosphonium salt (ylide) + C(8)-aldehyde or C(7 )-phosphonium salt (ylide) + C(8 )-aldehyde (D C(11)-phosphonium salt (ylide) + C(12)-aldehyde or C(11 )-phosphonium salt (ylide) + C(12 )-aldehyde (D C(15)-phosphonium salt (ylide) + C(15)-aldehyde... 

Calcyanide. See Calcium cyanide C-8 aldehyde. See n-Octanal C-9 aldehyde. See Nonanal CIO aldehyde. See Decanal C-16 aldehyde. See Ethyl methylphenylglycidate C-12 aldehyde, lauric. See Laurie aldehyde C-14 aldehyde, myristic. See Myristaldehyde Calendula. See Calendula officinalis Calendula extract. See Calendula officinalis extract... 

Synonyms Aldehyde C-8 C-8 aldehyde Caprylaldehyde Caprylic aldehyde n-Octaldehyde... 

Alcohol Alcohol C -10 Alcohol C-8 Aldehyde C -10 Aldehyde-Collidine Aldehydine... 

When the monoacetate (XXIV) reacts with periodate cyclization between the C-1 hydroxyl and C-8 aldehyde groups in the initial product gives the hemiacetal (XXV). The free aldehyde group is readily oxidized to give an acid whose methyl ester (XXVII R = H) can be acetylated to give the diacetate (XXVII R = Ac). The NMR-spectral data show... 

In other work, sulfone chemistry plays an integral part of the syntheses of both -carotene and vitamin A by workers at Kuraray. In this approach, the anion of C q P-cyclogeranyl sulfone (36) is condensed with the C q aldehyde (37). The resulting P-hydroxy sulfone (38) is treated with dihydropyran followed by a double elimination to yield vitamin A acetate. Alternatively, the P-hydroxy sulfone (38) can be converted to the 5-halo sulfone (39) and a similar double elimination scheme is employed (23,24) (Fig. 8). 

It was decided to construct a D-ring acylating agent bearing a latent C-8 vinyl group. To this end, benzylation of the known 5-bromo-orr/to-vanillin (22),14 followed by protection of the aldehyde carbonyl in the form of a cyclic acetal (1,3-dioxane), affords com-... 

Another synthesis, shown in Scheme 13.9, that starts with the same aldehyde (perillaldehyde) was completed more recently. The C(8)—C(9) bond was established by an allylic chlorination and addition of the corresponding zinc reagent to isobu-tyraldehyde. In this synthesis, the C(7) stereochemistry was established by a homogeneous hydrogenation of a methylene group, but this reaction also produces both stereoisomers. 

V.C.8.1. Alkenes and Alcohol Functions. Although TS-1 and other titanosi-licates oxidize alcohols to the corresponding aldehydes and ketones, the rates are suppressed in the presence of compounds containing C=C bonds. CH3OH, for example, is not oxidized at all during epoxidations of alkene reactants. Higher alcohols, however, are partially oxidized. The oxidation of unsaturated alcohols in the presence of TS-1 is shown in Table XVII (193). 

The cycloaddition of aldehydes and ketones with ketene under the influence of quinine or quinidine produce chiral 2-oxetanones [46,47]. Solvolytic cleavage of the oxetanone, derived from chloral, and further solvolysis of the trichloromethyl group leads to (5)- and (R)-malic acids with a 98% ee [46] (the chirality of the product depends on the configuration of the catalyst at C-8 and, unlike other alkaloid-induced reactions, it is apparently independent of the presence of the hydroxyl group). No attempts have been made to catalyse the reaction with chiral ammonium salts. 

In addition to the lack of sequence homology, ULPs have little structural homology to other DUB classes except in the active site. The structure of ULPl (see Figure 8.2) in complex with the C-terminal aldehyde of yeast SUMO (SMT3) illustrates that, like most other DUBs, ULPs are thiol proteases, utilizing a conserved catalytic triad consisting of an active-site cysteine, histidine, and aspartate [40]. 

Perlmutter used an oxymercuration/demercuration of a y-hydroxy alkene as the key transformation in an enantioselective synthesis of the C(8 ) epimeric smaller fragment of lb (and many more pamamycin homologs cf. Fig. 1) [36]. Preparation of substrate 164 for the crucial cyclization event commenced with silylation and reduction of hydroxy ester 158 (85-89% ee) [37] to give aldehyde 159, which was converted to alkenal 162 by (Z)-selective olefination with ylide 160 (dr=89 l 1) and another diisobutylaluminum hydride reduction (Scheme 22). An Oppolzer aldol reaction with boron enolate 163 then provided 164 as the major product. Upon successive treatment of 164 with mercury(II) acetate and sodium chloride, organomercurial compound 165 and a second minor diastereomer (dr=6 l) were formed, which could be easily separated. Reductive demercuration, hydrolytic cleavage of the chiral auxiliary, methyl ester formation, and desilylation eventually led to 166, the C(8 ) epimer of the... 

Since ketone R)-16 was prepared in a non-selective way when an achiral imino enolate was alkylated, it was considered whether alkylation of chiral enolates, such as that of oxazoline 18, with benzyl bromide 14, would provide stereoselective access to the corresponding alkylation product 19 with R-configuration at C(8) (Scheme 4). Indeed, alkylation of 18 with 14 gave the biaryl 19 and its diastereoisomer almost quantitatively, in a 14 1 ratio. However, reductive hydrolysis using the sequence 1. MeOTf, 2. NaBH4, and 3. H30", afforded hydroxy aldehyde 20 in 25% yield at best. Furthermore, partial epimerization at C(8) occurred (dr 7.7 1). An alternative route, using chiral hydrazones, was even less successful. 

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