Chirospecific synthesis of (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentane, precursor for carbocyclic nucleoside synthesis. Dieckmann cyclization with an .alpha.-amino acid
作者:Stephen C. Bergmeier、Agustin A. Cobas、Henry Rapoport
DOI:10.1021/jo00061a006
日期:1993.4
Carbocyclic nucleosides are important isosteres of nucleosides possessing a variety of antiviral and antineoplastic activities. We report here a new method for the chirospecific synthesis of (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentane. This compound is a key precursor for the synthesis of some carbocyclic nucleosides. The method involves (1) an improved synthesis of (S)-2-aminoadipic acid; (2) Dieckmann cyclization of this alpha-amino acid to an aminocyclopentanone; and (3) elaboration of the latter to the target (1S,3R)-l-amino-3-(hydroxymethyl)cyclopentane. The starting (S)-2-aminoadipic acid delta-methyl ester was prepared enantiomerically pure from (S)-aspartic acid in 51% overall yield. Dieckmann condensation converted this amino acid to a (methoxycarbonyl)-cyclopentanone, and reduction of the ketone followed by elimination yielded (S)-3-[N-(9-phenylfluoren-9-yl)amino]-1-(methoxycarbonyl)cyclopentene. Reduction of the double bond gave a mixture of the cis and trans diastereomers. This mixture was converted to a single diastereomer by epimerization and trapping of the cis isomer as (1S,4R)-2-(9-phenylfluoren-9-yl)-2-azabicyclo[2.2.1]heptan-3-one. Hydrolytic cleavage of the lactam followed by reduction gave (IS,3R)-1-amino-3-(hydroxymethyl)-cyclopentane.
Synthesis of an Azido Precursor to (2<i>S</i>,5<i>R</i>)-5-Hydroxylysine Using an Asymmetric Organocatalytic Chlorination/Reduction Sequence
作者:Manuel Johannes、Margaret A. Brimble
DOI:10.1021/jo402220s
日期:2013.12.20
An efficient, robust, and scalable synthesis of an azido precursor to the modified amino acid (2S,5R)-5-hydroxylysine was developed on the basis of the use of a highly stereoselective organocatalytic alpha-chlorination-reduction protocol. The final Fmoc-protected (2S,5R)-6-azido-5-hydroxylysine derivative can be used in solid-phase peptide synthesis, providing access to proteins that contain large quantities of post-translationally modified lysine (e.g., collagens).