Synthesis of?,?-unsaturated amino acids via ester enolate Claisen rearrangement of chelated allylic esters

Proline Ester Enolate Claisen Rearrangement and Formal Total Synthesis of (-)-Cephalotaxine

A concise formal total synthesis of (-)-cephalotaxine was achieved via an ester enolate Claisen rearrangement (EECR). A series of EECRs of proline allyl esters were examined to obtain the desired relative stereochemistry of an azaspiranic tetracyclic backbone. An unexpected reversal or low diastereoselectivity of ( Z)-cinnamyl ester was observed. The diastereoselectivity was controlled by substitution patterns of a styrene region. This result represents a useful guide in aiding the prediction of stereochemical outcome of EECR of α-amino allylic esters.

Total synthesis of the natural HDAC inhibitor Cyl-1

A chelate enolate Claisen rearrangement was used as a key step in the first total synthesis of Cyl-1, a cyclic tetrapeptide from Cylindrocladium scoparium.

Diastereotopos-differentiating allylic alkylation as a key step in the synthesis of gamma-glutamyl boletine

A straightforward approach towards gamma-glutamyl boletine is described, based on a diastereotopos-differentiating allylic alkylation of chelated amino acid ester enolates. Independent of the configuration of the leaving group in the allylic substrate, the allylation product is obtained as a single stereoisomer. Its configuration is solely controlled by the stereogenic center adjacent to the pi-allyl complex formed.

Highly diastereoselective anti-aldol reactions of glycolate titanium enolates

Diastereoselective aldol reactions of enolates of alpha-hydroxy ester with different aldehydes are metal tunable, providing either anti- or syn- products. The highest anti-selectivities were obtained with TiCl(OiPr)(3), while Ti(OiPr)(4) provides the opposite syn-products.

Syntheses of optically active 2-amino-4-oxobutyric acid and N,O-protected derivatives

Strategies for the synthesis of optically active aspartaldehyde derivatives are reviewed. Most of them are using the chiral pool: allylglycine or naturally occurring homoserine, aspartic acid or methionine and side chain modifications. This will be developed in the first part. Some other original routes are also displayed in the second part. Different aspects of each strategy are discussed: the nature and number of steps, the problem of protecting groups, the price and availability of starting materials. Some synthetic applications of such interesting chiral synthons are shown in the last part.