Construction of side chain

Alkylation of chiral triflates with organomagnesium or organolithium reagents for construction of side chains of naturally occurring heterocycles, antibiotics, and enzyme inhibitors 99YGK334. 

Stereoselective synthesis of heterocyclic amino alcohols 82S6O5. Stereospecific construction of side chains in syntheses of natural hetero-... 

N. L. Summers, M. Karplus. Construction of side-chains in homology modelling Application to the C-terminal lobe of rhizopuspepsin. J. Mol. Biol. 1989, 210, 785-811. 

Binder and Kluger [41, 42] utilized the Hamilton wedge and THY as molecular recognition handles in the construction of side-chain-functionalized poly(oxanorbornene dicarboximides) using a ROMP/click methodology. Monomers functionalized with azido or alkynyl side chains were polymerized to either homopolymers or block copolymers and subsequently subjected to Cu-catalyzed azide-alkyne cycloaddition [72] to install the desired H-bonding motifs. 

Scheme 1-292. Stereoselective construction of side chains based on [3,2]-migrations.

In many ways, the molecular models that we have used as the basis for our CAMD studies describe coal structure very well. However, none of the models investigated thus far contains explicit three-dimensional covalent cross-links. Actualfy, the models we have studied are primarily constructed of long chains of one-dimensionally-linked clusters with a number of short side-chains. However, it has been established on the basis of solvent swelling studies (11.15.16) that bituminous coal is primarily made up from a three-dimensional network of clusters held together by covalent bonds and by an even higher density of hydrogen bonds. These macromolecular models of coal, which are less concerned with the molecular structure than with the ways that clusters are bonded to one another, provide a complementary way of describing coal structure. 

A recent synthesis of zincophorin methyl ester by Cossy and coworkers employs allenylzinc methodology to construct a side chain anti,syn stereotriad (Figure l)26. 

A key contribution of molecular dynamics simulations to the imderstanding of mechanisms of selectivity and affinity in TBP-DNA complexes is the discovery of the active role of TBP in the formation of the complex. The view derived from crystal structures was that of a passive role for the TBP which only imposed a steric constraint on DNA shape. It appears now from the simulations that TBP can respond to the dynamics of the bound DNA sequence by adjusting its interdomain geometry, and this might be relevant for the construction of the final preinitiation complex. Furthermore, many of the contacts characterized in the crystal structures were found in the simulations to have an important dynamic component, as side chains switch rotamers rather frequently. This conformational freedom makes it possible for TBP to achieve suitable binding contacts with a variety of DNA moieties in a dynamic mode which contributes to enthalpic stabilization. However, the extent of preservation of side chain dynamics in the complex is dependent on the local structure. As it reduces the entropy loss upon complex formation, it provides an additional source of sequence-dependent gain in affinity that is revealed for the first time from the results of the molecular dynamics simulations. 

In our synthesis of brassinosteroids, organoaluminum chemistry was proved to be useful in constructing the side-chain double bond with the desired geometry, and the stereoselective cleavage of epoxides was shown to be an excellent method to generate the correct configuration of the side-chain. 

The Wittig reaction has been used to construct the side-chain in a synthesis of (-)-sirenin (208), a water mold sperm-attacking hormone.ii The intermediate (206) was generated, without competing formation of the structural isomer (207), by reaction of the ylide (205) with (204) under salt-free conditions in DME. Standard Wittig methods have been used to construct the side-chain in an enantioselective synthesis of (+)-(7 , 9Z)-methyl trisporate (209) and its (9E)-isomer.l 12 The reaction of triphenyl-(vinylimino)phosphorane derivatives (210) with tropones provides a convenient synthesis of 1-aza-azulenes (211) and (212) in either one or two steps (Scheme 28).H The mechanism of the one-step reaction was investigated using deuterium-labelled tropane derivatives. 

The ylide (158) and dimethyl 4>(methoxycarbonyl)-2 (oxobutyl)phosphonate have been used to construct the side chains in the first reported synthesis of the major metabolite (159) of PGDg. Wittig reactions with polyether ylides, e.g., (160), have been used to construct the side chains in the synthesis of a variety of furan-based secoprostacyclins. ... 

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