C-acylation of cyclopropanols: preparation of functionalized 1,4-diketones.

A convenient method for preparing attractively functionalized 1,4-diketones has been devised by palladium-catalyzed cross-coupling of cyclopropanols and acyl chlorides. The utility of this method has been demonstrated in an enantioselective synthesis of (+)-myrmicarin 217.

Practical syntheses of proposed and revised manzacidin B and their congeners.

A concise and highly stereoselective total synthesis of manzacidin B and its congeners has been developed following chelation-controlled syn-epoxidation and Lewis acid catalyzed intramolecular regioselective epoxide ring opening to generate the quarternary amine center. Elaboration of the triol moiety to the target molecule was achieved in good overall yield, representing practical total syntheses of manzacidin B and its congeners. From the XRD, NMR, and analytical data, the correct structure of natural manzacidin B, (4R,5R,6R)-6, was confirmed.

Ring-closing metathesis (RCM) based synthesis of the macrolactone core of amphidinolactone A.

A convergent synthesis of the macrolactone core of amphidinolactone A has been achieved, in a 10 step linear sequence with 32% overall yield, through a ring-closing metathesis reaction as the macrolactonization step. The RCM precursor was obtained by the union of acid and alcohol fragments derived from (R)-epichlorohydrin and (R)-2,3-O-isopropylidene glyceraldehyde, respectively.

Sub-cellular internalization and organ specific oral delivery of PABA nanoparticles by side chain variation.

Background: Organic nanomaterials having specific biological properties play important roles in in vivo delivery and clearance from the live cells. To develop orally deliverable nanomaterials for different biological applications, we have synthesized several fluorescently labelled, self-assembled PABA nanoparticles using possible acid side chain combinations and tested against insect and human cell lines and in vivo animal model. Flurophores attached to nanostructures help in rapid in vivo screening and tracking through complex tissues.

Iodocyclization and Prins-type macrocyclization: an efficient formal synthesis of leucascandrolide A.

The formal total synthesis of leucascandrolide A has been achieved in 20 steps from a known epoxide with an overall yield of 11.5% following a recently developed strategy for the construction of trans-2,6-disubstituted-3,4-dihydropyrans and a Lewis acid catalyzed intramolecular Prins-cyclization of an aldehydic homoallylic alcohol to generate the tetrahydropyran ring with three stereogenic centers and macrocycle concomitantly.

Stereoselective synthesis of four possible isomers of streptopyrrolidine.

The synthesis of (4R,5R)-streptopyrrolidine (1), (4S,5R)-streptopyrrolidine (2) (4R,5S)-streptopyrrolidine (3) and (4S,5S)-streptopyrrolidine (4) have been achieved in a concise and highly efficient manner via a highly stereoselective aldol type reaction with the trimethylsilyl enolate of ethyl acetate and Lewis acid mediated lactamization as the key reactions in ≈42% yield over six steps starting from D-phenylalanine and L-phenylalanine, respectively. The absolute configuration of the natural product was shown to be (4S,5S) by comparing its spectral and analytical data with the reported values.

Iodo-cyclizations: novel strategy for the total syntheses of polyrhacitide A and epi-cryptocaryolone.

Highly stereoselective total syntheses of polyrhacitide A and epi-cryptocaryolone have been achieved in 11 steps with high overall yield of 24% and 28%, respectively, following a recently developed strategy for the construction of trans-2,6-disubstituted-3,4-dihydropyrans. In this report, the versatility of iodo-cyclization for the total syntheses of polyrhacitide A and epi-cryptocaryolone is demonstrated.

4-N-pyridin-2-yl-benzamide nanotubes compatible with mouse stem cell and oral delivery in Drosophila.

p-aminobenzoic acid (PABA), a structural moiety of many commercial drugs, is self-assembled with linker alkyl side chains to form tubular nanostructures. The tubes exhibited fluorescence either intrinsic or from fluorescent molecules embedded in the wall during self-assembly. Uptake and inter-cellular delivery of the conjugated nanotubes in human cancer cells and in mouse embryonic stem cells were demonstrated by fluorescence imaging and flow cytometry.

Iodine-catalyzed highly diastereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans: application to concise construction of C28-C37 bicyclic core of (+)-sorangicin A.

A novel iodine-catalyzed highly diastereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans have been achieved from delta-hydroxy alpha,beta-unsaturated aldehydes by treating with allyltrimethyl silane in THF at room temperature with good to excellent yields. This methodology has been successfully implemented for a concise asymmetric synthesis of C28-C37 dioxabicyclo[3.2.