Abstract
Five-membered cyclic α-hydroxy acids (1-hydroxycycycloalkane-1-carboxylic acids) are important constituents in biologically active natural products and also important precursor molecules for the synthesis of pharmacologically active compounds. This paper presents stereo selective synthesis of polysubstituted five-membered bicyclic α-hydroxy acid derivatives from α, α, α-dialkylated 1,3-dixolan-4-one (9). The synthesis was initiated on the α-propagylation of 2-(tert-butyl)-5-(1-ethenylprop-2-enyl)-1, 3-dixololan-4-one (trans-8) via its enolate, followed by intramolecular Pauson-Khand cyclization. The reaction was stereo selective and afforded two isomers (10a and 10b) in 4:1 ratio out of four possible diastereoisomers of bicyclic α-hydroxy acid (bicyclic 1-hydroxycarboxylic acid) derivatives. This method opens a new avenue to prepare synthetically useful highly functionalized stereoselctive synthesis of five-membered bicyclic α-hydroxy acids using a convenient and very effective method.
Highlights
Cyclic -hydroxy carboxylic acids are important constituents in pharmacological active natural products and important synthetic building units for the synthesis of various biologically active natural products [1]
Glycolic acids is an available, important -hydroxy acid which can be converted into the asymmetric acetals, and it can serve as chiral auxiliaries in selective induction of its -position to prepare asymmetric 1-hydroxycycloalkane-1-carboxylic acid derivatives [3]
We reported stereo selective preparation of 1-hydroxycylclopentene-1-carboxylic acid derivatives (3, Figure 1) using chiral equivalent of glycolate derivatives via metathesis
Summary
Cyclic -hydroxy carboxylic acids are important constituents in pharmacological active natural products and important synthetic building units for the synthesis of various biologically active natural products [1]. We reported stereo selective preparation of 1-hydroxycylclopentene-1-carboxylic acid derivatives (3, Figure 1) using chiral equivalent of glycolate derivatives via metathesis. This method has been successfully applied in the synthesis of natural product, (-)-quinic acid [4]. In another method, we have demonstrated synthesis of polysubstituted 1-hydroxyclyopentane-1-carboxylic acid derivatives (6a and 6b, Figure 2) using chiral equivalent of glycolate derivatives via a group selective radical annulation procedure [5]. As a demonstration of the proposed method, we explain here the synthesis of asymmetric polysubstituted bicyclic 1-hydroxycarboxylic acids (10a and 10b, Figure-5) using glycolate derivatives synthesized via simple reactions process (Figure 3 & 4)
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