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Synthesis of bicyclic scaffolds has gained significant attention in drug discovery due to their potential to mimic benzene bioisosteres. Here, we present a mild and scalable Sc(OTf)3‐catalyzed [3+2] cycloaddition of bicyclo[1.1.0]butanes (BCBs) with ynamides, yielding a diverse array of polysubstituted 2‐amino‐bicyclo[2.1.1]hexenes in good to excellent yields. These products offer valuable starting materials for the construction of novel functionalized bicyclo[1.1.0]butanes. Preliminary mechanistic studies indicate that the reaction involves a nucleophilic addition of ynamides to bicyclo[1.1.0]butanes, followed by an intramolecular cyclization of in situ generated enolate and keteniminium ion. We expect that these findings will encourage utilization of complex bioisosteres and foster further investigation into BCB‐based cycloaddition chemistry. [ABSTRACT FROM AUTHOR]

Keywords: chiral phosphoric acid; organocatalysis; cycloaddition; alkenes; alkynes EN chiral phosphoric acid organocatalysis cycloaddition alkenes alkynes 1200 1214 15 06/19/23 20230704 NES 230704 1 Introduction Asymmetric cycloaddition reaction is the most powerful strategy for the construction of various enantioenriched carbocycles and heterocycles, [1] because it provides an efficient and completely atom-economical route from simple precursors. In order to achieve this goal, we needed to overcome the following issues: (1) realization of efficient cycloaddition of alkynes with appropriate partners; (2) the installation of suitable groups onto alkynes to avoid free rotation around the potential C-C axes; (3) the choice of a competent chiral catalyst to promote the designed cycloaddition reactions and to control the stereoselectivity. 3 CPA-Catalyzed Cycloaddition of Alkynes Although the CPA-catalyzed cycloaddition of alkenes have been well documented, the CPA-catalyzed asymmetric cycloaddition reaction of alkynes is still lacking. On the other hand, the cycloaddition of alkynylnaphthols with imines proceeded via a sequential [4+2] cycloaddition, an alkyne-type Povarov cycloaddition, and an auto-oxidation reaction. [Extracted from the article]

To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau (QTP) responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades (A, B and C). Analysis of molecular variance (amova) revealed that most of the genetic variability was found within populations (0.693), while differentiations between populations were obviously distinct ( Fst= 0.307). Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago (kya) were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu's FS values and ‘ g’ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum (LGM) and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages. [ABSTRACT FROM AUTHOR]

C23H17NO4, orthorhombic, P212121 (no. 29), a = 26.3525(8) Å, b = 3.88640(10) Å, c = 34.8871(10) Å, V = 3573.01(18) Å3, Z = 8, Rgt(F) = 0.0419, wRref(F2) = 0.1086, T = 180 K. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that geological or climatic events in the past promoted allopatric speciation of alpine plants in the Qinghai-Tibetan Plateau and adjacent region. However, few studies have been undertaken to examine whether such allopatric divergences also occurred within a morphologically uniform species. In the present study, we report the evolutionary history of an alpine shrub species, Hippophae tibetana, based on examining chloroplast DNA (cpDNA) and nuclear ribosomal internal transcribed spacer (ITS) DNA variations. We sequenced two cpDNA fragments ( trnL-F and trnS-G) and the nuclear ITS region in 183 individuals collected from 21 natural populations. Ten chlorotypes and 17 ITS types were identified. Phylogenetic analyses of both chlorotypes and ITS sequence variations suggested two distinct lineages distributed in the eastern and western region, respectively. On the basis of the fast and low plant substitution rates, these two lineages were estimated to have diverged from each other between 1 and 4 million years ago, during the period of the major glaciations and orogenic processes. In addition, ITS has undergone the accelerated evolution in two populations in the southern Himalaya isolated by the high mountains with a surprising accumulation of the private variations. The east-west split was also supported by an analysis of molecular variance, which partitioned around 91% of the total cpDNA variance between these two groups of populations. A single chlorotype was found for most populations in eastern or western region, suggesting a recent postglacial expansion within each region. Star-phylogeny and mismatch analyses of all chlorotypes within the eastern group of populations suggested an earlier regional expansion before the Last Glacial Maximum (LGM). The local fixture of the different chlorotypes in multiple populations suggested more than one refugia remained for eastern or western region. Coalescent tests rejected the hypothesis that all current populations originated from a single refugium during the LGM. Instead, they supported hypothesis that two lineages diverged before the late Pleistocene. These findings, when taken together, suggested that this species had experienced long allopatric divergence and recent regional range expansions in response to orogenic processes and the climate changes. The evolutionary history of this shrub species highlights importance of geographical isolations to the intraspecific divergence of alpine plants occurring in the world's ruff. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, , 37-50. [ABSTRACT FROM AUTHOR]

C20H19Cl4N3O3S, monoclinic, P21/c (no. 14), a = 14.2134(9) Å, b = 21.4083(13) Å, c = 7.6709(5) Å, β = 99.260(6)°, V = 2303.7(2) Å3, Z = 4, Rgt(F) = 0.0659, wRref(F2) = 0.1682, T = 180 K. [ABSTRACT FROM AUTHOR]