Ketones, functional group

Ketose (Section 25.1) A carbohydrate with a ketone functional group. 

Based on a known synthesis of spiro compounds with six-membered rings [63] we succeeded in the stepwise assembly of terminal substituted mono-[64] and dispiranes [65]. Hereby the cyclisation of the dibromide 35 with TOSMIC (Iter. 1) is the keystep of the reaction sequence as the initial ketone functional group (36) is recovered. Four subsequent reactions led to the spirodibromide 40 (Iter. 2). Final spirocyclisation afforded the dispirane 41, representing a precursor for new calamitic liquid crystals (Fig. 16) [66]. 

Derivatives of hydrazine, especially the hydrazide compounds formed from carboxylate groups, can react specifically with aldehyde or ketone functional groups in target molecules. Reaction with either group creates a hydrazone linkage (Reaction 44)—a type of Schiff base. This bond is relatively stable if it is formed with a ketone, but somewhat labile if the reaction is with an aldehyde group. However, the reaction rate of hydrazine derivatives with aldehydes typically is faster than the rate with ketones. Hydrazone formation with aldehydes, however, results in much more stable bonds than the easily reversible Schiff base interaction of an amine with an aldehyde. To further stabilize the bond between a hydrazide and an aldehyde, the hydrazone may be reacted with sodium cyanoborohydride to reduce the double bond and form a secure covalent linkage. 

It is easily seen why it is called MEK (methyl ethyl ketone). There is a methyl group to the left of the ketone functional group and an ethyl group to the right of the ketone group. 

For most of the reactions of monosaccharides that involve the aldehyde or ketone functional group, the presence of open chain form is crucial, as only in this form do these functional groups exist. A sugar solution contains two cyclic anomers and the open chain form in an equilibrium. Once the aldehyde or ketone group of the open chain form is used up in a reaction, the cyclic forms open up to produce more open chain form to maintain the equilibrium. 

The diazomethyl ketone functional group was first observed to be an affinity label by Buchanan and co-workers who showed that the antibiotic azaserine, an O-diazoacetyl derivative, 9 inhibited an enzyme in the biosynthesis of purine by alkylation of a cysteine residue. 10 The acid protease pepsin was then observed to be inhibited by peptidyl diazomethyl ketones in the presence of copper ions with the resulting esterification of an aspartate residue. 11 Two peptidyl diazomethyl ketones, Z-Phe-CHN2 and Z-Phe-Phe-CHN2, were found to irreversibly inactivate papain, a cysteine protease. 12 Since these reports, many peptidyl diazomethyl ketones have been prepared primarily as inhibitors of various cysteine proteases. 7 Peptidyl diazomethyl ketones are also synthetic intermediates and have been used to prepare chloromethyl ketones (Section 15.1.3), 13 bromomethyl ketones (Section 15.1.3), acyloxymethyl ketones, 14 and (i-peptides. 15 A few peptidyl diazoalkyl ketones have been reported. 16,17 ... 

Only one method has been used to prepare various peptidyl diazomethyl ketones. A protected amino acid or peptide acid is activated as the mixed anhydride and reacted with ethereal diazomethane at low temperature. Generally a peptide with the desired sequence is prepared first and then converted into the diazomethyl ketone in the final step of the synthesis. Since the diazomethyl ketone functional group is stable to alkali but unstable to acid, acidic conditions used to deprotect many peptide protecting groups must be avoided. 

Aldehyde and ketone functional groups are also present in many biologically important compounds. Glucose and most other sugars contain aldehyde groups, for instance. Testosterone and many other steroid hormones contain ketone groups. 

A carbohydrate contains many V f hydroxyl groups and either an aldehyde or ketone functional group. A simple carbohydrate (monosaccharide or sugar) is an aldose if it contains an aldehyde group, or a ketose if it contains a ketone group. 

Hydrazide groups directly react with aldehyde and ketone functional groups to form relatively stable hydrazone linkages (Chapter 2, Section 5.1). Two fluorescein derivatives are commonly available that contain hydrazide groups off their No. 5 carbons on the lower ring structure. Both may be used to label fluorescently aldehyde- or ketone-... 

In solution, very few sugar molecules exist with free aldehyde or ketone functional groups. Aldehydes and hydroxyls in a sugar... 

You can also catalytically reduce aldehydes and ketones to produce 1° and 2° alcohols. Reduction conditions are very similar to those used to reduce alkene double bonds. If a molecule possesses both a double bond and an aldehyde or ketone functional group, reduction of the aldehyde or ketone group is best carried out using sodium borohydride. The reduction of cyclohexanone by hydrogen gas with a platinum catalyst produces cyclohexanol in good yield. 

Methyl-2-butanone can in fact be simplified to 3-methylbutanone because there is only one possible place for the ketone functional group in this molecule. In case the carbonyl C = O group is at the end of the chain it would be an aldehyde and not a ketone. Numbering is also not necessary in locating an aldehyde group since it can only be at the end of a chain ... 

First we note that it is necessary to form a carbon-carbon bond because the starting material has only two carbons and the target has seven. Because the starting material is an alkyne, we can probably use an acetylide anion as the nucleophile to form the carbon-carbon bond (see Section 10.8). How can a ketone functional group be introduced Section 11.6 described the hydration of an alkyne to produce a ketone. Our retrosynthetic analysis then becomes ... 

Most of the compounds that you have encountered in this text so far have been fairly simple. In addition to any carbon-carbon double or triple bonds, they have contained only one functional group and could be named by using suffixes such as -ynol or -dienone. However, for a compound that contains more than one heteroatom functional group, only one of these functional groups can be designated in the suffix. For example, consider the following compound, which has both alcohol and ketone functional groups ... 

Peptide Chloromethyl Ketones. Peptide chloromethyl ketone inhibitors have been studied extensively and a fairly detailed picture of the inhibition reaction (see Figure 3) has emerged from numerous chemical and crystallographic studies (30,31). The inhibitor resembles a serine protease substrate with the exception that the scissile peptide bond of the substrate is replaced with a chloromethyl ketone functional group in the inhibitor. The inhibitor binds to the serine protease in the extended substrate binding site and the reactive chloromethyl ketone functional group is placed then in the proper position to alkylate the active-site histidine residue. In addition, the serine OH reacts with the inhibitor carbonyl group to form a hemiketal. 

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