Amides conjugated esters

The photochemistry of linearly conjugated 2,4-cyclohexadiene-l-ones (e.g. 4) has been studied extensively7. These linearly conjugated systems generally photorearrange to a (Z)-dienylketene 5 (equation 1) this process is usually reversible, so that in the absence of a nucleophile little change is observed. In the presence of amines or alcohols, however, amides and esters are typically isolated. In the presence of weaker nucleophiles a slow formation of phenol derived products is usually observed. 

Amides are very weak bases, far too weak to attack alkyl halides, so they must first be converted to their conjugate bases. By this method, unsubstituted amides can be converted to N-substituted, or N-substituted to N,N-disubstituted, amides.914 Esters of sulfuric or sulfonic acids can also be substrates. Tertiary substrates give elimination. O-Alkylation is at times a side reaction.915 Both amides and sulfonamides have been alkylated under phase transfer conditions.916... 

The combinations of chlorotrimethylsilane-hexamethylphosphoramide (HMPA) or chlorotrimethylsi-lane-4-(dimethylamino)pyridine (DMAP) are also powerful accelerants for copper(I)-catalyzed Grignard conjugate additions,33 and stoichiometric organocopper and homocuprate additions (Scheme 21 ).36 However, these reactions must be performed in tetrahydrofuran instead of ether.37 These procedures are noted for their high yields with stoichiometric quantities of Grignard reagents, excellent chemoselectivity and efficiency with a,3-unsaturated amides and esters and enals.58 Typically, additions to enals proceed via the S-trans conformers to afford stereo-defined silyl enol ethers for example, enals (122) and (124) give the ( )-silyl enol ether (123) and (Z)-silyl enol ether (125), respectively. 

Geraldes, C. F.,A. D. Sherry, W. P. Cacheris, K.-T. Kuan, R. D. Brown, S. H. Koenic, M. Spillers. 1988. Number of inner-sphere water molecules in feteland Ei + complexes of DTPA-amide and -ester conjugates. Magn. Reson. MedB 191-199. 

The amine function served also as the starting point for the first covalent linkage of Pcs to single-walled carbon nanotubes (SWNTs) [94], The pipes with open-end and surface-bound acyl chloride moieties were used to prepare the Pc-SWNTs system by amide-bond formation (Fig. 14). Accordingly, statistical reaction of 4-aminophthalonitrile with 4-tcr/-bu(yIph111alonitrile in the presence of zinc ions delivered the monoamino Pc that was then employed in the conjugation with the acid chloride modified carbon nanotubes (CNTs). Here, it should also be mentioned that other functions have been applied to the covalent modification of CNTs, i.e., amide [95], ester [96,97], or click chemistry [98],... 

Conjugate addition of a silylcuprate reagent (34) to the a,(3-unsaturated acid amide or ester of a pertinent chiral amine or alcohol, respectively, is an alternative route to (3-silyl amides and esters. Conjugate addition of a cuprate reagent to a P-silyl acrylamide also gives a chiral P-silyl amide. The diastereomeric excess of the newly produced chiral center is fairly high, as summarized in Scheme 14." ... 

Using a chiral auxiliary via an amide or ester leads to asymmetric induction. Aryl aldehydes and conjugated ketones were condensed using proline, leading to modest enantioselectivity. °° Chiral biaryl catalysts have been used with trialkyl-phosphines, giving good enantioselectivity. ° Chiral quinuclidine catalysts lead to... 

Fig. 3 A tumor-targeted polymer-drug conjugate. The major elements include (i) a polymeric drug-carrier that is water-soluble, bicompatible or biodegradable, non-immunogenic (ii) targeting moieties (iii) a linker between a drug and the carrier. The linker can be a) a chemical bond such as ester or amide. An ester bond is more stable at lysosomal pH than at plasma pH (7.4) while an amide bond is stable at both lysosomal and plasma pH b) an oligopeptide linker that is degradable by specific enzymatic hydrolysis and c) an acid labile linker that is degradable at lysosomal pH but stable at plasma pH.

Reagent (42) is readily prepared " by the treatment of primary and secondary amines and hydrazines (substituted or unsubstituted) or the corresponding hydrochlorides with trimethylaluminum. The aluminum amide reagents (42) readily react with a variety of ester substrates, such as conjugated esters (entries 2,5 and 11, Table 16 " ), N-blocked amino acid esters (entry 10, Table 16), as well as alkyl esters (en-... 

FIGURE 40.18 Structures of BPAA/CyD amide and ester conjugates. 

---