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A series of bioinspired transformations that are applied to convert strictosidine aglycones into monoterpenoid indole alkaloids is reported. The highly reactive key intermediates, strictosidine aglycones, were prepared in situ by simple removal of a silyl protecting group from the silyl ether derivatives, and converted selectively via bioinspired transformations under substrate control into heteroyohimbine‐ and corynantheine‐type, and akagerine and naucleaoral related alkaloids. Thus, concise, divergent total syntheses of 13 monoterpenoid indole alkaloids, (−)‐cathenamine, (−)‐tetrahydroalstonine, (+)‐dihydrocorynantheine, (−)‐corynantheidine, (−)‐akagerine, (−)‐dihydrocycloakagerine, (−)‐naucleaoral B, (+)‐naucleidinal, (−)‐naucleofficines D and III, (−)‐nauclefiline, and (−)‐naucleamides A and E, were accomplished in fewer than 13 steps. [ABSTRACT FROM AUTHOR]

Anti-infectious strategies against pathogen infections can be achieved through antiadhesive strategies by using multivalent ligands of bacterial virulence factors. LecA and LecB are lectins of Pseudomonas aeruginosa implicated in biofilm formation. A series of 27 LecA-targeting glycoclusters have been synthesized. Nine aromatic galactose aglycons were investigated with three different linker arms that connect the central mannopyranoside core. A low-nanomolar ( Kd=19 n m, microarray) ligand with a tyrosine-based linker arm could be identified in a structure-activity relationship study. Molecular modeling of the glycoclusters bound to the lectin tetramer was also used to rationalize the binding properties observed. [ABSTRACT FROM AUTHOR]

An artificial nucleoside surrogate with 1H-imidazo[ 4,5-f][1,10]phenanthroline (P) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal-mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective AgI-mediated base pairs strongly depends on the sequence context. Quantum mechanical/ molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B-DNA duplex. [ABSTRACT FROM AUTHOR]

The first total synthesis of the branched oligosaccharide OSE-1 of Mycobacterium gordonae (strain 990) is reported. An intramolecular aglycon delivery approach was used for constructing the desymmetrized 1,1′-α,α-linked trehalose moiety. A [3+2] glycosylation of the trisaccharide donor and trehalose acceptor furnished the right hand side pentasaccharide. Regioselective O3 glycosylation of L-rhamnosyl 2,3-diol allowed expedient synthesis of the left hand side tetrasaccharide. The nonasaccharide was assembled in a highly convergent fashion through a [4+5] glycosylation. [ABSTRACT FROM AUTHOR]

Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the synthesis of these molecules. Key aspects of our final strategy include 1) synthesis of the C1-C9 pyran core ( 5) using an AuCl3-catalysed cyclisation; 2) formation of C10-C22 vinyl iodide ( 55) by sequential bidirectional Stille reactions and 3) diastereoselective union of these advanced fragments by means of an alkenylzinc addition (d.r.=91:9 at C9). The common callipeltoside aglycon ( 4) was completed in a further five steps. Following this, all three sugar fragments were appended to provide the entire callipeltoside family. In addition to this, D-configured callipeltose B was synthesised and appended to the callipeltoside aglycon. The 1H NMR spectrum of this molecule was found to be significantly different to the natural isolate, further supporting our assignment of callipeltoside B ( 2). [ABSTRACT FROM AUTHOR]

We have developed a method for recyclable hypervalent-iodine-mediated direct dehydrogenative α,β′- bifunctionalization of β-ketoesters and β-diketones under metal-free conditions, which affords a straightforward way to synthesize benzo-fused 2,3-dihydrofurans. This efficient, mild method, which has a wide substrate scope and good functional-group tolerance, was used for the multistep synthesis of the protected aglycone of a naturally occurring phenolic glycoside. A mechanism involving Michael addition to an enone intermediate and subsequent oxidative cyclization is proposed. [ABSTRACT FROM AUTHOR]

A series of eight stereoisomeric N-(tetrahydroxy bicyclo-[5.1.0]oct-2 S*-yl)phthalimides were prepared in one to four steps from N-(bicyclo[5.1.0]octa-3,5-dien-2-yl)phthalimide (±)- 7, which is readily available from cyclooctatetraene (62 % yield). The structural assignments of the stereoisomers were established by 1H NMR spectral data as well as X-ray crystal structures for certain members. The outcomes of several epoxydiol hydrolyses, particularly ring contraction and enlargement, are of note. The isomeric phthalimides as well as the free amines did not exhibit β-glucosidase inhibitory activity at a concentration of less than 100 μ M. [ABSTRACT FROM AUTHOR]

Described herein is the expansion of the picoloyl protecting-group assisted H-bond mediated aglycone delivery (HAD) method recently introduced by our laboratory. At first it was noticed that high α-stereoselectivity is only obtained with S-ethyl glycosyl donors and only in the presence of dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST), in high dilution, and low temperature. Combining the mechanistic studies of the HAD reaction and bromine-promoted glycosylations allowed a very effective method to be devised that allows for highly stereoselective α-glycosidation of practically all common leaving groups ( S-phenyl, S-tolyl, S/ O-imidates) at regular concentrations and ambient temperature. [ABSTRACT FROM AUTHOR]

Bioinspired transformation, divergent syntheses, monoterpenoid indole alkaloid, strictosidine, total synthesis Keywords: bioinspired transformation; divergent syntheses; monoterpenoid indole alkaloid; strictosidine; total synthesis EN bioinspired transformation divergent syntheses monoterpenoid indole alkaloid strictosidine total synthesis 1 1 1 02/21/22 20220221 NES 220221 B Strictosidine is an important molecule b in the biosynthesis of higher plants that gives rise to a great variety of structures. [Extracted from the article]