Bifunctional building blocks

The enantioselective isomerization of bifunctional Cs-isoprenoid allylamines to optically active bifunctional aldehydes was developed by using Rh(l)+/( )-BIPHEMP as the catalyst (Scheme 2).17 These aldehydes are useful optically active bifunctional building blocks for isoprenoid homologation. 

In addition, ortto-lithiation of halopyridines with bulky bases such as LDA was followed by reaction with RsSnCl to produce the desired halostannylpyridines as bifunctional building blocks [54,55]. 

Fig. 22 Lithocholic acid-derived homo-bifunctional building blocks... 

Keywords Cyclopeptides Depsipeptides Peptoids Macrocycles Diketopiper-azines Benzodiazepines Ugi-reaction Polycyclic compounds Orthogonal reactivity Sequential reactions Iteration Bifunctional building blocks Medium sized rings Beta-turn motif... 

SCHEME 15. Synthesis of bifunctional building blocks through copper/Taniaphos-catalyzed allyhc alkylation... 

The utility of the copper/Taniaphos-catalyzed allylic alkylation was further illustrated in two subsequent reports. The application of aliphatic allylic bromides containing protected alcohols and amines leads to the efficient synthesis of bifunctional building blocks (Scheme 15) . ... 

Abstract How to access efficiently the macrocyclic structure remained to be a challenging synthetic topic. Although many elegant approaches/reactions have been developed, construction of diverse collection of macrocycles is stiU elusive. This chapter summarized the recently emerged research area dealing with multi-component synthesis of macrocycles, with particular emphasis on the approach named multiple multicomponent reaction using two bifunctional building blocks . 

Multiple Multicomponent Macrocyclization Using Two Bifunctional Building Blocks... 

Scheme 17 Synthesis of macrocycles by multiple multicomponent reactions including bifunctional building blocks (MiBs)...

Mediated enzyme electrodes were also realized on combined microscale and nanoscale supports [300]. Bioelectrocatalytic hydrogels have also been realized by co-assembling electron-conducting metallopolypeptides with bifunctional building blocks [301]. More recently, redox-modified polymers have been employed to build biofuel cells [25, 70, 302, 303]. In 2003, an enzymatic glucose/02 fuel cell which was implanted in a living plant was introduced [147]. 

Wheeldon, I.R., Barton, S.C., and Banta, S. (2007) Bioactive proteinaceous hydrogels from designed bifunctional building blocks. Biomacromolecules, 8, 2990-2994. 

Lactone Cleavage, Analogous to esters, lactones are also efficiently cleaved with TMS-I to provide ta-iodocarboxylic acids, which may be further functionalized to afford bifunctional building blocks for organic synthesis (eq 7). Diketene reacts with TMS-I to provide a new reagent for acetoacylation. ... 

For selected examples, see (a) G. Zhao, X. Sun, H. Bienayme, J. Zhu, J. Am. Chem. Soc. 2001, 123, 6700-6701. Activation of a terminal carboxylic acid by an internal oxazole a novel synthesis of macrocyclodepsipeptide. (b) P. Janvier, M. Bois-Choussy, H. Bienayme, J. Zhu, Angew. Chem. Int. Ed. 2003, 42, 811-814. A one-pot four-component (ABC ) synthesis of macrocycles, (c) L. A. Wessjohann, E. Ruijter, Mol. Divers 2005, 9, 159-169. Macrocycles rapidly produced by multiple multicomponent reactions including bifunctional building blocks (MiBs). (d) C. Bughin, G. Zhao, H. Bienayme, J. Zhu, Chem.-Eur. J. 2006, 12, 1174-1184. 5-Aminooxazole as an internal traceless activator of C-terminal carboxylic acid rapid access to diversely functionalized cyclodepsipeptides. (e) T. Pirali, G. C. Iron, J. Zhu, Org. Lett. 2006,8,4145 148. One-pot synthesis of macrocycles by a tandem three-component reaction and intramolecular [3 +2] cycloaddition. 

F. Leon, D. G. Rivera, L. A. Wessjohann, J. Org. Chem. 2008, 73, 1762-1767. Multiple multicomponent macrocychzations including bifunctional building blocks (MiBs) based on Staudinger and Passerini three-component reactions. 

In a fundamental research context, the directionality and strength of the interactions are of prime importance. When a single type of interaction dominates the interaction between bifunctional unimers, it is easy to understand and describe the relation between molecular structure and macroscopic properties. While the directionality and strength of the interactions between unimers are also important when developing applications for supramolecular polymers, the use of multifunctional instead of bifunctional building blocks is often an efficient way to achieve the desired properties. However, for applications there are a number of requirements that are sometimes difficult to meet. The most challenging of these are synthetic availability, cost, and stability of appropriate functional groups. 

Propargylic alcohols, which possess inherent alkynyl and hydroxyl functional groups, are one of the most valuable bifunctional building blocks in the field of organic synthesis. Very recently, Zhan and co-workers described the synthesis of substituted pyrazoles 40 via AgOTf-catalyzed cascade propargylic... 

One-pot macrocyclization can start from either symmetric or unsymmetrical bifunctional monomers. As discussed in Sect. 9.3.1 and for symmetric bifunctional building blocks, it was demonstrated by Gong and his co-workers that longer oligomers such as a trimeric diamine and a trimeric diacid chloride preferentially... 

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