BOC-L-Phenylalanine

Stereoselective synthesis of pseudo C2-symmetrical 1,3-dibenzyldiamino alcohol (S,S) (323) a core unit of HIV protease inhibitors, and the two meso-stereoisomers (323a) and (323b) was achieved by stereocontrolled addition of benzylmagnesium chloride to nitrones (63a) and (63b) (Scheme 2.137). The yield of (S,S)-(323), based on N-Boc-L-phenylalaninal, accounts for 23% (Scheme 2.137) (211). 

The crude diazo ketone (30.8-33.4 g) always contains about 10% of Boc-L-phenylalanine methyl ester formed by esterification of Boc-L-phenylalanine with diazomethane. This material can be carried through the synthesis and is removed during Step B. 

Another possible way of overcoming the limitations posed by the presence of water in the suspension polymerisation process is to substitute the continuous water phase with alternative solvents that could still act as dispersing medium for the monomer mixture but better preserve noncovalent interactions in the template-monomer assembly. For example, liquid fluorocarbons are chemically inert and do not affect interactions which are used in noncovalent imprinting. Use of such solvents for the preparation of MIP microbeads has been demonstrated already in 1996 by Mayes and Mosbach [16,17]. A range of MIPs were prepared using Boc-l-phenylalanin as the template, MAA as the functional monomer and different kinds and amounts of crosslinkers and porogenic solvents. The resulting MIP microbeads... 

Only a few attempts were reported concerning the arrangement of MIP particles between two porous membranes, or their deposition on a single membrane. For example, Lehmann et al. used MIP nanoparticles with diameters between 50 nm and 300 nm imprinted with boc-L-phenylalanin-anilide obtained by miniemulsion polymerisation the selective rebinding properties as well as the hydrodynamic properties of the nanoparticles stacked between two polyamide membranes were studied [254]. 

BOC-L-Isoleucine BOC-Glycine BOC-L-Phenylalanine Hydrogen fluoride Ethylmethyl sulfate... 

Indolinone (—)-154 was transformed into the key imine intermediate (- -)-155 smoothly in just a few step reactions. Treatment of (- -)-155 with A-Boc-L-phenylalanine and p-methoxyphenyl (PMP)-isonitrile at room temperature provided 78% yield of ipeptide (- -)-156 via the stereoselective Ugi three-component reaction. Noteworthily, the isonitrile attacks predominantly on the side opposite the bulky 1,1-dimethylallyl group of imine (+)-155 in the Ugi reaction, which was then transformed into (—)-fmctigenine A 157 in just a few steps. Alternatively, the Ugi reaction of (- -)-155 with A-Boc-D-alanine and isonitrile 158 stereoselectively provided 71% yield of tripeptide (- -)-159, which was then transformed into (—)-5-A-acetylardeemin 160 in just a few steps. 

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