The design and synthesis of head-to-tail linked artificial macrocycles using the Ugi-reaction has been developed. This synthetic approach of just two steps is unprecedented, short, efficient and works over a wide range of medium (8–11) and macrocyclic (≥12) loop sizes. The substrate scope and functional group tolerance is exceptional. Using this approach, we have synthesized 39 novel macrocycles by two or even one single synthetic operation. The properties of our macrocycles are discussed with respect to their potential to bind to biological targets that are not druggable by conventional, drug-like compounds. As an application of these artificial macrocycles we highlight potent p53-MDM2 antagonism.
A visible-light photoinduced fragmentation borylation of O-phthalimido cycloalkanols with bis(catecholato)diboron is described. Structurally diverse keto and formyloxy alkyl boronic esters are shown to be conveniently prepared by radical-mediated ring-opening of cyclic alcohols and hemiacetals, respectively. The reactions proceed under mild conditions in the absence of additives or photocatalysts, display excellent functional group tolerance, and are shown to allow cleavage of 4-, 5-, 6-, and 7-membered ring substrates. The mechanism proceeds via sequential homolytic N-O and C-C bond cleavages, the latter of which involves β-scission of an alkoxy radical, generating a carbonyl and an alkyl radical that is trapped by the diboron reagent. Spectroscopic studies suggest direct photoexcitation of either the phthalimide or diboron substrates with blue-light can initiate a radical chain mechanism.
An effective reflexive-Michael (r-M) reaction has been disclosed to access drug-like six-membered spirooxindoles in good yields and excellent enantioselectivities by using an aminoenyne-catalysis.
Biologically important, less‐explored natural products of sexually deceptive chiloglottones, antimicrobial dialkylresorcinols, and their many analogues were synthesized in very good yields in a sequential two‐pot manner by using an “organocatalytic reductive coupling reaction” as the key step.
An enolate-mediated organocatalytic azide-ketone [3+2]-cycloaddition (OrgAKC) reaction of a variety of enolizable arylacetones and deoxybenzoins with aryl azides was developed for the synthesis of fully decorated 1,4-diaryl-5-methyl(alkyl)-1,2,3-triazoles in excellent yields with high regioselectivity at 25 °C for 0.5-6 h. This reaction has an excellent outcome with reference to reaction rate, yield, regioselectivity, operation simplicity, and availability of substrates and catalyst. This reaction has advantages over the previously known metal-mediated reactions.
A general approach to asymmetric synthesis of highly substituted spirodihydrocoumarins with a quaternary stereocenter was achieved through neighboring ortho-hydroxyl group induced sequential Michael-lactonization reactions on 2-(2-nitrovinyl)phenols with alkyl cyclopentanone-2-carboxylates in the presence of a catalytic amount of quinine-NH-thiourea followed by p-TSA.
Asymmetric synthesis of drug-like functionalized spiro[chroman-3,3'-indolin]-2'-ones 5 containing three contiguous stereocenters with high diastereo- and enantioselectivities was achieved using the reflexive-Michael (r-M) reaction of unmodified hydroxyenals 1 with various (E)-3-alkylideneindolin-2-ones 2 in the presence of (R)-DPPOTMS/AcOH (R)-3/4b as a catalyst at room temperature. Chiral spiro[chroman-3,3'-indolin]-2'-ones 5 were transformed into the functionalized spiranes 7, 9, and 10 in good yields with high selectivity through Wittig, TCRA, acetal protection and reduction reactions, respectively. Supporting evidence for the reaction pathway through the formation of the important catalytic species of "aminals" was observed through NMR and ESI-HRMS analysis of an ongoing reaction between 1 and (R)-3 in CDCl3 and also shown by the structural requirement in hydroxyenals 1 to generate the “aminals” with (R)-3 through controlled experiments.
The
morpholine and piperazine with their remarkable physical and
biochemical properties are popular heterocycles in organic and medicinal
chemistry used in rational property design. However, in the majority
of cases these rings are added to an existing molecule in a building
block approach thus limiting their substitution pattern and diversity.
Here we introduce a versatile de novo synthesis of the morpholine
and piperazine rings using multicomponent reaction chemistry. The
large scale amenable building blocks can be further substituted at
up to four positions, making this a very versatile scaffold synthesis
strategy. Our methods thus fulfill the increasing demand for novel
building block design and nontraditional scaffolds which previously
were not accessible
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