Synthesis functional group interconversion

The synthesis of both haliclamines A (64) and B (65) has been achieved (Scheme 6). The first synthesis of both 64 and 65 [35,36] was a convergent approach starting from the monoprotection and functional group interconversions (FGls) of 1,4-butanediol (66) to the monoprotected iodide (67), which... 

The heart of organic synthesis is the orchestration of functional group interconversions and C—C bond forming steps. 

Hydrogen atom transfer implies the transfer of hydrogen atoms from the chain carrier, which is the stereo-determining step in enantioselective hydrogen atom transfer reactions. These reactions are often employed as a functional group interconversion step in the synthesis of many natural products wherein an alkyl iodide or alkyl bromide is converted into an alkane, which, in simple terms, is defined as reduction [ 19,20 ]. Most of these reactions can be classified as diastereoselective in that the selectivity arises from the substrate. Enantioselective H-atom transfer reactions can be performed in two distinct ways (1) by H-atom transfer from an achiral reductant to a radical complexed to a chiral source or alternatively (2) by H-atom transfer from a chiral reductant to a radical. 

So far we have discussed only the use of molecular imprinting for the synthesis of enzyme-like catalytic polymers with hydrolytic and carbon-carbon bond forming properties. However, in the past decade, a number of research groups have worked on another important application, the functional groups interconversion. The next section will describe some of the most significant reports that have appeared in the literature during the past decade. 

The replacement of halogen by an amino functionality is important in many syntheses of natural products. This can be performed simply by nucleophilic substitution or by other methods such as the Gabriel synthesis. These functional group interconversions are discussed below. 

Many of the standard functional group interconversions are described in synthetic schemes involving the pyrrolopyrimidines. In order to conserve space, only a few illustrative examples are shown here. The references cited in Section 7.07.6.2 on synthesis should be consulted for further examples. 

Amine synthesis using functional group interconversions... 

Thus, in order to understand the synthesis of a complex molecule, we need to understand the carbon-carbon bond forming reactions, functional groups interconversions and stereochemistry aspects. 

FUNCTIONAL GROUP INTERCONVERSIONS AS STRATEGIC TOOLS IN A TOTAL SYNTHESIS... 

If the product has more carbon-carbon o bonds than the starting material, the synthesis must form one or more C-C bonds. If not, only functional group interconversion occurs. 

Reaction of a cyclopropane with diazomethane or an azide generated cyclopropanes containing an azo function " a similar cycloaddition was reported for a nitri-limine. Cycloaddition of an ethandiylidene biscyclopropane and triazolinedione led to a hydrazine derivative Reactions of these types forming azo- or hydrazinocyclopro-panes are not subject of this review however, they could be of interest for aminocyclop-ropane synthesis by functional group interconversion (for the cycloaddition of cyclopropyl azide with a carbon-carbon double bond see Section II.E.3, equation 101). 

For the synthesis of organic compounds, two types of reaction are used C,C-bond-form-ing reactions for the construction of large structures from small units, and functional group interconversion for introduction of the functionality into the target molecule and for activation of the building blocks [44]. 

Retrosynthetic analysis involves the disassembly of a TM into available starting materials by sequential disconnections and functional group interconversions. Structural changes in the retrosynthetic direction should lead to substrates that are more readily available than the TM. Synthons are fragments resulting from disconnection of carbon-carbon bonds of the TM. The actual substrates used for the forward synthesis are the synthetic equivalents (SE). Also, reagents derived from inverting the polarity (IP) of synthons may serve as SEs. 

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