Kasireddy Krishnudu

A simple and efficient PdCl2 mediated conversion of γ,δ-olefinic alcohols into C-glycosides

Abstract An efficient and mild intramolecular oxidative nucleophilic cyclisation protocol has been developed for the conversion of γ, δ-olefinic alcohols into the hemiketals, which in turn on deoxygenation led to the very important C-glycoside class of compounds.

Pd (OAc)2 mediated oxidative cyclisation of γ,δ - olefinic alcohols: A new route to C-vinyl furanosides

Abstract An intramolecular oxidative cyclisation protocol, making use of the Pd(OAc) 2 NaOAcO 2 system in DMSO, has been developed for the efficient conversion of sugar derived γ,δ -olefinic alcohols into the C-vinyl furanoside class of compounds.

Radical reactions on furanoside acetals: First synthesis of sporothriolide and 4-epi- ethisolide from ‘diacetone glucose’

Abstract First synthesis of sporothriolide (1) and 4- epi -ethisolide (2) is described, where the crucial bicyclo[3.3.0]octane systems 3 and 4 have been made by the adoption of regio- and stereoselective intramolecular radical cyclisation reaction onto the ‘chirons’ derived from ‘diacetone glucose’.

Pd(II)Cl2 mediated oxidative cycllsation of some 3-hydroxy 4-vinyl furanoside derivatives to synthetically valuable bis-furanosides

PdCl2 mediated oxidation of 3-hydroxy-4-vinylfuranosides (Ia-k) lead to the formation of aldehydes, some of them are ‘in situ’ trapped as their lactols (IIIa,c,e,f,h) and further converted to bis-furanoside lactones IVa,c,e,f,h).

Clay montmorillonite in carbohydrates: Use of ‘claysil’ as an efficient heterogenous catalyst for the intramolecular Ferrier reactions leading to 1,6-anhydro rare saccharides☆

Abstract Clay montmorillonite supported silver reagent - claysil - was prepared and advantageously used in the intramolecular Ferrier reaction of 6-hydroxy glycals 1a–9c . The unsaturated sugars 13a–21c so obtained were stereoselectively hydroxylated leading to the rare 1,6-anhydro saccharides 22a–30c . Synthesis of (D)-allosan ( 31 ) and (D)-gulosan ( 34 ) is described.

‘Off template site’ [3+3] annulation reaction on sugar derived enal: stereoselective synthesis of C–C-linked pseudo-saccharide precursors

Abstract A [3+3] annulation protocol at an ‘off template’ site of a sugar-derived enal synthon is used effectively for the stereoselective synthesis of C–C-linked pseudo-saccharide precursors. The chirality is induced from the sugar synthon during the installation of carbocycle at the C-5 of sugar template.

Radical mediated stereoselective synthesis of chiral spiroacetals from enol-esters

Stereoselective synthesis of chiral spiroacetals starting from enol-ester 1, derived from d-manno lactone, is described. The strategy involves 1,4-addition of a variety of alcohols to 1 in the presence of NBS to give α-bromo acetals, which undergo a regio- and stereoselective radical cyclisation to give highly functionalised chiral spiroacetals.

Radical reactions on furanoside acetals: A formal synthesis of (−)-canadensolide from D-mannose

Abstract By adaption of an intramolecular radical cyclisation protocol to the furanoid glycal derivative 3 derived from D-mannose, synthesis of the crucial bicyclo[3.3.0]octane system 6 is reported. A sequence of reactions on this key synthon 6 , leading to the formal synthesis of (−)-canadensolide ( 1 ) is described.

Radical cyclisation approach for the first synthesis and determination of absolute stereochemistry of discosiolide from diacetone glucose

Abstract By the adoption of a regio- and stereoselective intramolecular radical cyclisation reaction onto a chiron derived from diacetone glucose, the crucial cis -fused bicyclo[3.3.0]octane system was made and utilized for the first synthesis of discosiolide 1 , thereby establishing the absolute stereochemistry of the natural product.

Stereoselective synthesis of highly oxygenated cyclohexanes through a [3+3] annulation approach

Abstract The synthesis of highly oxygenated cyclohexanes has been achieved through a Michael–Wittig protocol via a [3+3] annulation of the enal that is derived from 2,3-O-isopropylidene-(R)-glyceraldehyde. The γ-alkoxy enal system is responsible for the stereoselectivity.