Formation of the BC ring system of upenamide via a Staudinger/aza-Wittig reaction

The BC ring system of upenamide was assembled using a stereoselective Diels-Alder reaction followed by a Staudinger/aza-Wittig/imine hydrolysis reaction. Stereoselective aldol coupling with an aldehyde that incorporates the DE ring system led to an advanced synthetic intermediate en route to the marine alkaloid upenamide.     

Efficient Synthesis of Quinolines via a Knoevenagel/Staudinger/aza-Wittig Sequence

A simple and efficient method for the construction of quinoline derivatives from 2-azidobenzaldehyde and various carbonyl compounds was developed. The process involves a Knoevenagel condensation of 2-azidobenzaldehyde with carbonyl compound and subsequently an intramolecular normal Staudinger/aza-Wittig reaction to form the quinolone ring in satisfactory yields.     

De novo synthesis of oligosaccharides using a palladium-catalyzed glycosylation reaction

The natural all d- and/or unnatural all l-1,4- and 1,6-oligosaccharides were synthesized from furan alcohols using a palladium-catalyzed glycosylation reaction. The 1,4- and 1,6-alpha-manno-disaccharides were achieved in seven total steps starting from chiral furan alcohols. Similarly, 1,4- and 1,6-alpha-manno-trisaccharides were also synthesized in nine total steps. Key to the overall efficiency of this process was the use of highly diastereoselective palladium-catalyzed glycosylations, reductions, and dihydroxylations.     

De novo synthesis of deoxy sugar via a Wharton rearrangement

A highly divergent synthesis of α-fuco-, α-6-deoxy-allo-, α-6-deoxy-altro-pyranosides has been achieved. This route utilizes a Wharton rearrangement as part of a new post-glycosylation transformation strategy.     

De novo asymmetric synthesis of homoadenosine via a palladium-catalyzed N-glycosylation

[reaction: see text] A highly stereoselective synthesis of l-2-deoxy-beta-ribo-hexopyranosyl nucleosides from 6-chloropurine and Boc-protected pyranone has been developed. Our approach relies on the iterative application of a palladium-catalyzed N-glycosylation, diastereoselective reduction, and reductive 1,3-transposition. This strategy is amenable to prepare various natural and unnatural hexopyranosyl nucleosides analogues.     

Microwave-assisted synthesis of dinucleoside analogues containing a thiazolidin-4-one linkage via one-pot tandem Staudinger/aza-Wittig/cyclization

Dinucleosides containing a thiazolidin-4-one linkage were prepared by one-pot tandem Staudinger/aza-Wittig/intermolecular cyclization under microwave irradiation and their structures were confirmed. Preliminary examination of HIV-RT inhibition showed that the dinucleosides containing (R)-thiazolidin-4-one linkage are significantly more active than those containing (S)-thiazolidin-4-one linkage.     

Switch peptide via Staudinger reaction

A new transformation based on the Staudinger reaction is described, and its application in the design of a novel switch element to control peptide folding is demonstrated. We found that the azide switch is activated rapidly in water to promote acyl transfer using tris(2-carboxyethyl)phosphine hydrochloride (TCEP) via the Staudinger reaction. Our findings expand the repertoire of uses of the Staudinger reaction in chemical biology and the number of available triggers for use in switch peptides.     

杂环合成中的氮杂Wittig反应

氮杂Wittig反应是杂环化合物的一个新的合成方法.本文阐述了羰基通过叠氮化物和三价膦形成的亚胺基膦的作用, 以氮杂Wittig反应的方式, 合成含氮杂环化合物的进展.     

De novo synthesis of galacto-sugar δ-lactones via a catalytic osmium/palladium/osmium reaction sequence

A highly efficient route to various 1,5-galacto-sugar lactones from dienoates has been developed by using three catalytic reactions. These reactions include (i) an enantioselective osmium-catalyzed dihydroxylation, (ii) a regio- and diastereoselective palladium-catalyzed π-allyl alkylation with p-methoxyphenol for alcohol differentiation and protection, and (iii) a diastereoselective dihydroxylation that can be improved using matched enantioselective osmium-catalyzed dihydroxylation condition.     

De novo synthesis of a galacto-papulacandin moiety via an iterative dihydroxylation strategy

A short and highly efficient route to both the pyranose and furanose forms of a galacto-papulacandin ring system has been developed. The key to the overall transformation is the sequential two osmium-catalyzed dihydroxylation reactions of substituted 2,4-dienone. The resulting tetrol can be efficiently transformed into the two spiroketal moieties of galacto-papulacandin, which can also be inter-converted via acid catalyzed equilibration.     

Unexpected synthesis of 2,4,5-trisubstituted oxazoles via a tandem aza-Wittig/Michael/isomerization reaction of vinyliminophosphorane

2,4,5-Trisubstituted oxazoles 6 were unexpectedly prepared from a tandem reaction of vinyliminophosphorane 3 with various acyl chlorides in a one-pot fashion.     

Stereocontrolled synthesis of fully functionalized D-glucosamine monosaccharides via a domino nitro-Michael/Henry reaction

A diastereoselective domino nitro-Michael/Henry reaction involving a beta-hydroxyaldehyde and a nitroalkene provides direct access to fully functionalized D-glucosamine monosaccharides.     

De novo synthesis of natural products via the asymmetric hydration of polyenes

For the last ten years our group has been working toward the development of an asymmetric hydration approach to polyketide natural products based on the regioselective hydration of di- and tri-enoates. Key to the success of this approach is the recognition that both high regiocontrol and asymmetric induction could be obtained by the use of a Sharpless asymmetric dihydroxylation reaction. Herein we describe the development of the method and its application to natural product total synthesis.     

De novo synthesis of (+)-isofregenedol

An efficient enantioselective synthesis of (+)-isofregenedol was achieved in 13 steps from commercially available cyclohexene oxide without the use of protecting groups. The tetrahydronaphthalenic core of isofregenedol was obtained via a gold(I)-catalyzed benzannulation recently developed in our laboratory.     

New efficient synthesis of 2,3,4-trisubstituted 3,4-dihydroquinazolines by a Ugi 4CC/Staudinger/aza-Wittig sequence

A series of 2,3,4-trisubstituted 3,4-dihydroquinazoline 3 was prepared by intramolecular aza-Wittig reaction of amide carbonyl groups with methyldiphenyl iminophosphorane, which was obtained from a Ugi 4CC/Staudinger sequence. Further intramolecular Heck reaction of 3d′-g′ in the presence of catalytic amount of Pd(OAc)₂ gave 6,12-dihydroindolo[2,1-b]quinazolines 4a-d in good yields.     

De novo synthesis of Tamiflu via a catalytic asymmetric ring-opening of meso-aziridines with TMSN3

An asymmetric ring-opening reaction of meso-aziridines with TMSN3 was developed using a catalyst prepared from Y(OiPr)3 and chiral ligand 2 in a 1:2 ratio. Excellent enantioselectivity was realized from a wide range of substrates with a practical catalyst loading. The products were efficiently converted to enantiomerically enriched 1,2-diamines, which are versatile chiral building blocks for pharmaceuticals and chiral ligands. This reaction was applied to a catalytic asymmetric synthesis of Tamiflu, a very important anti-influenza drug containing a chiral 1,2-diamino functionality.     

An approach to the synthesis of dimeric resveratrol natural products via a palladium-catalyzed domino reaction

A route for the rapid assembly of the carbon framework of several resveratrol natural products is presented. A palladium-catalyzed domino reaction of bromostilbene derivative 6 and tolane 7, involving two sequential Heck coupling reactions, provides access to the benzofulvene-based core of various resveratrol-derived natural products. The carbon skeleton of pallidol and its congeners is achieved by a Lewis acid-induced Nazarov-type oxidative cyclization of 9.     

De novo synthesis of thiophenes on a polymeric support

The Hinsberg thiophene synthesis was expanded to support bound thioglycolic acid derived synthons, which reacted with arils to give thiophenes in high purity.