Smart and concise entry to chiral spiro[cyclopentane-indolizidine]-tetraol diastereomers as a new aza-spirocyclic framework

Abstract

Dihydrofuro[2,3-f]indolizidinone obtained from biosourced L-glutamic acid (L-GA) was used advantageously as an advanced building block to prepare affordably in a few steps optically pure spiro[cyclopentane-indolizidine]-tetraol diastereomers as a new oxacarba-spiroindolizidine framework. The sequential approach used for the construction of tetracyclic spiro-compounds’ core consists of olefin cis-dihydroxylation, diol protection, and α-carbonyl alkylation followed by alkene ring-closing metathesis as the key step. Chiral oxacarba-spiroindolizidine tetraols were obtained by the sequence of steps consisting of alkene cis-dihydroxylation, diol protection and lactam carbonyl reduction followed ultimately by acetonide deprotection.