Synthesis of side chain

The Michael addidon of nitto compounds is a useful method for the preparadon of various naniral products The Michael kldidon of nittoalkanes to dehydroalanines gives ynitto-ct-amino acids, which provides a convenient synthesis of side-chain modified ct-amino acids fEq 4 114 " Transformadons of Y-nitto-ct-amino acid derivadves into ct-amino adds occur by... 

A Aletras, K Barlos, D Gatos, S Koutsogianni, P Mamos. Preparation of the very acid-sensitive Fmoc-Lys(Mtt)-OH. Application in the synthesis of side-chain to side-chain cyclic peptides and oligolysine cores suitable for solid-phase assembly of MAPs and TASPs. Ini J Pept Prot Res 45, 488, 1995. 

Transformation of a phosphonio-substituted phospholide derivative under conservation of the r-electron system has been demonstrated in a number of cases which include substitution of a ring-hydrogen atom, replacement of a PRs -moiety by a hydride, or reductive de-arylation of a PhsP " - to a phosphinyl substituent PPh2. Subsequent re-quaternisation of the latter allows the formal substitution of a PhsP " - by a modified Ph2(R)P -moiety in a two-step reaction. The application of this scheme is not only perfectly suitable for the synthesis of bis-phosphonio-benzophospholides with different phosphonio-moieties but, since the last reaction stage tolerates a variety of functional groups in the electrophile, offers as well a convenient pathway for the synthesis of side-chain functionalised phosphonio-phospholide derivatives from more simple substituted precursors. 

Synthesis of Side-Chain-to-Side-Chain and Head-to-Side-Chain Cyclic Peptides... 

Scheme 8. Synthesis of side-chain 35 as the t-butyl ester.

Synthesis of Side-Chain Conformationally Restricted a-Amino Acids... 

Synthesis of Side-Chain-Substituted Oxazolidine-4-carboxylic Add Peptides... 

The disadvantage of this method is that saponification of the resulting ester group can result in racemization. A method for the synthesis of TV-methyl amino acids without esterification has been presented by Benoiton and co-workers,[78 95] which uses sodium hydride as the base and iodomethane in THF at room temperature. This method is also applicable to the synthesis of side-chain-functionalized amino acid derivatives when the side chain is protected by a terf-butyl-type group. 

Scheme 2 Synthesis of Side-Chain-Protected Peptides Employing the Oxime Resin,2l...

Enantiomerically pure a-amino aldehydes containing nonpolar side chains such as Boc-Ala-H, Boc-Leu-H, and Boc-Phe-H are synthesized by lithium aluminum hydride reduction of the corresponding Weinreb amides, Boc-Ala-N(Me)OMe, Boc-Leu-N(Me)OMe, and Boc-Phe-N(Me)OMe, respectively (Table 4). The lithium aluminum hydride does not affect the Boc group due to the low temperature and short 15-minute reaction time. Successful synthesis of side-chain Bzl-protected Boc-Thr(Bzl)-H gives a 95% yield of crude product, however, reduction of N-protected aspartyl and glutamyl aldehydes from their corresponding A-methoxy-A-methylamides leads to overreduction and unreacted hydroxamateJ1920 ... 

Cyclopentadienyl compounds of lithium, sodium, potassium, magnesium and thallium are most commonly used. The synthesis of these cyclopentadienyl-transfer agents is described in more detail in Section II.B.2. Organosilicon halides and alkoxides are the most convenient substrates. The synthesis of side-chain functionalized cyclopentadienyl silanes is described in equation 541,42 as a typical example of this strategy. 

Our initial work involved the synthesis of side chains which have the molecular characteristics required for a nonlinear optical response. Compounds 1-3 were prepared by the use of Horner-Emmons-Wadsworth Wittig methodology (22). Compound 4 was commercially available (Aldrich) as the dye, Disperse Red 1. As outlined in Scheme I, in the first step in the synthesis of 1-3,... 

Scheme 3. Synthesis of side-chain modified compounds 94 and 95.

Easton, C. J. Roselt, P. D. Tiekink, E. R. T. Synthesis of side-chain functionalized amino add derivatives through reaction of alkyl nitro-nates with a-bromoglydne derivatives. Tetrahedron 1995, 51, 7809-7822. 

Crombie, L., Edgar, A.J.B., Harper, S.H., Lowe, M.W., and Thompson, D. 1950. The synthesis of the pyrethrins. V. Synthesis of side-chain isomers and analogs of cinerone, cine-rolone, and cinerin-I. Journal of Chemical Society, 3552-63. 

T. Takata, H. Kawasaki, N. Kihara, Y. Furusho, Synthesis of Side-Chain Polyrotaxane by Radical Polymerizations of Pseudorotaxane Monomers Consisting of Crown Ether Wheel and Acrylate Axle Bearing Bulky End-Cap and Ammonium Group , Macromolecules, 34, 5449 (2001)... 

Synthesis of Side-chain Carboxy Acids.—The side-chain carhoxy acids being really aryl substituted aliphatic acids are synthesized by methods characteristic of such acids. 

By Grignard Reaction.—Exactly analogous to the Grignard synthesis of ring carboxy acids is the synthesis of side-chain carboxy acids by the introduction of carbon dioxide into the Grignard reagent. 

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