Carlo Bonini

Highly regioselective opening of optically active N-Boc-2,3-aziridino alcohol derivatives with metal halides

Abstract Chiral 3-substituted N-Boc-2,3-aziridino alcohols are opened in a regio and stereoselective fashion by MgBr 2 ; the obtained 3-bromo derivatives can be reduced and deprotected under mild conditions to the corresponding 1,2-amino alcohols.

Singlet oxygen degradation of lignin

Abstract Lignin obtained by steam explosion of straw, beech (a hardwood plant), and pine (a softwood plant) was isolated and characterized by using standard methods. The irradiation of lignins with visible light in the presence of oxygen and of a singlet oxygen sensitizer (Rose Bengal) induced several modifications in the lignin structures that were monitored by using gel permeation chromatography (GPC) and UV spectroscopy. We observed a remarkable reduction of the mass distribution by GPC when monitoring at 280 nm and the shift of the residual chromatograms to mass values lower than the native lignins. These data are in agreement with a depolymerization reaction of lignins. The UV spectra showed that all the chemical species of lignins undergo several modifications during the irradiation reaction. Thus, the E 1 band reduced its absorbance and underwent a hypsochromic shift. The E 2 , and the B band were greatly reduced during the irradiation.

Regioselective opening of 3-Substituted N-Ethoxycarbonyl aziridine-2-carboxylates with metal halides toward the preparation of α and β-amino acids

Abstract 3-Substituted N-Ethoxycarbonyl aziridine-2-carboxylates are opened in a regio and stereoselective fashion whether in C-2 position by NaX (X = 1, Br) or in C-3 by MgBr 2

A general protocol for the regio high yielding opening of different glycidol derivatives

Abstract Differently protected glycidol derivatives (with Bn, TBDPS, TBS and MPM groups) have been tested for regioselective ring opening with vinylmagnesium bromide in order to obtain useful five-carbon functionalised homoallylic alcohols. Careful choice of the reagents and experimental conditions allowed a general access to important chiral synthons for asymmetric synthesis.

Metal halide-mediated opening of three membered rings: enantioselective synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and (3R)-3-aminodecanoic acid

Abstract Regio and stereoselective opening of three membered rings by metal halides was utilized for the enantioselective synthesis of (2 S ,3 R )-3-amino-2-hydroxydecanoic acid and (3 R )-3-aminodecanoic acid.

Oxirane rings: studies and applications of a new chemo and regio selective reductive opening of epoxides

Abstract the straightforward reductive opening of 1,2 epoxides to alcohols was studied and applied to several significant compounds. The reaction, which proceeds via the nucleophilic opening of the oxirane ring and the subsequent free radical dehalogenation, shows an excellent chemical yield as well as chemo and regioselectivity. This reaction was also applied to a chiral α,β-epoxyester.

A study on the chelation control in the regioselective opening of 2,3-bifunctionalized epoxides

Abstract The results obtained in the MgBr 2 -mediated opening of 2,3-bifunctionalized epoxides are reported. The studies showed that the chelation control of MgBr 2 between different functionalities can in some cases be selective.

Novel N-(2-benzo[b]thienyl)iminophosphoranes and their use in the synthesis of benzo[b]thieno[2,3-b]pyridines

Novel N-(2-benzo[b]thienyl)iminophosphoranes react with α,β-unsaturated aldehydes and ketones to give benzo[b]thieno[2,3-b]pyridines in an aza-Wittig/electrocyclic-ring closure process. The diphenylmethyliminophosphorane reacts with aromatic and heteroaromatic aldehydes to give iminic products: upon UV irradiation, two imines furnish cyclization products in acceptable yields.

A simple route to syn α-Amino-β-Hydroxy esters by C-2 regioselective opening of a, β-Epoxy esters with metal halides

Abstract α,β-Epoxy esters are opened by NaX (X = I, Br) in a regio and stereoselective fashion to β-hydroxy-α-halo esters, which represent suitable precursors of syn α-amino-β-hydroxy esters and β-hydroxy esters.

Studies on asymmetric synthesis of β-hydroxy-δ-lactone inhibitors of HMGCoA reductase 1. A new preparation of the lactone moiety of compactin

Abstract a new strategy for the preparation of chiral β-hydroxy-δ-lactone inhibitors of HMGCoA reductase is outlined: in particular the compactin lactone moiety has been elaborated by asymmetric epoxidation of the appropriate allylic alcohol and subsequent introduction of the second chiral center via a new Ti(OiPr)4 mediated reduction of β-hydroxy ketones.