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Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

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2.1.3.5 <strong>Synthesis</strong> fiom #-<strong>Amino</strong> <strong>Acids</strong><br />

Scheme 2.14<br />

Scheme 2.15<br />

Clearly, the most straightforward method for the synthesis <strong>of</strong> p-hydroxy-a-amino<br />

acids is the derivatization <strong>of</strong> senne <strong>and</strong> threonine. In particuiar, the serine aldehyde<br />

equivalents 1.50-1.53 described in section 1.3.4.1 are capable <strong>of</strong> producing 2S,3R/2R,3S<br />

(syn or threo) <strong>and</strong> 2S93S/2R,3R (anti or erythro) diastereomers.<br />

Rapopon's serinal equivalent 1.50 has been reacted with various organometallic<br />

reagents to give ketone 2.32 which is diastereoselectively reduced with L-Selectride to<br />

give the syn alcohol in ratios <strong>of</strong> 99: 1 to 9: 1 depending on the alkyl group or to the anti<br />

product with LiBfi in 6: 1 selectivities (Scheme 2.16)? Oxidation <strong>and</strong> deprotection to<br />

the amino acid was not reported.

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