Xiong-Li Liu

Construction of Pyrrolidinyl Spirooxindoles via a 1,3-Dipolar Cycloaddition Reaction of (E)-N-Boc-3-Alkylidene-Indolin-2(3H)ones with Azomethine Ylides

Abstract A mild and efficient method for the construction of pyrrolidinyl spirooxindoles via a 1,3-dipolar cycloaddition reaction of (E)-N-Boc-3-alkylidene-indolin-2(3H)ones with azomethine ylides has been established. The presence of an N-Boc group in the indolin-2(3H)ones obviously increased the activity and stereoselectivity of the reaction, affording the desired pyrrolidinyl spirooxindoles 4 with up to 85% yield and up to >99/1 dr value. Furthermore, the antibacterial activity of these compounds against Staphylococcus aureus (ATCC-25825) has been tested at minimum concentration, and some of them exhibit moderate antibacterial activity. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Molecular Hybridization-Guided One-Pot Multicomponent Synthesis of Turmerone Motif-Fused 3,3'-Pyrrolidinyl-dispirooxindoles via a 1,3-Dipolar Cycloaddition Reaction

Described herein is the development of a facile and efficient methodology for the synthesis of novel turmerone motif-fused 3,3′-pyrrolidinyl-dispirooxindoles 3–5 via a multicomponent 1,3-dipolar cycloaddition of dienones 2 with azomethine ylides (thermally generated in situfrom isatins and proline or thioproline or sarcosine). Products bearing four or three consecutive stereocenters consist of two oxindole moieties and a pyrrolidinyl core, including vicinal spiroquaternary stereocenters fused in one ring structure were smoothly obtained in high yields (up to 93% yield) with good diastereoselectivity (up to >20:1). Another valuable application of this method was for the design of new hybrid architectures for biological screening through the adequate fusion of these sub-units of turmerone and 3,3′-pyrrolidinyl-dispirooxindole, generating drug-like molecules.

Et2NH catalysis-enabled construction of convolutamydine A-fused morusignin L-scaffolds and their biological evaluation for anticancer activities

ABSTRACT Described herein is a facile and efficient methodology toward the synthesis of novel convolutamydine A-incorporated morusignin L scaffold 3 from an aldol addition event of carbonyl compounds to isatins through enamine catalysis. Products featuring a quaternary carbon center were smoothly obtained in good yields (up to 85% yield). This protocol also represents the first construction of flavonoid skeleton-fused oxindole molecules, thus leading to new knowledge in the fields of both molecular complexity and diversity synthesis and the lead compound discovery. Furthermore, their biological activities against human prostate cancer cells PC-3 and human leukemia cells K562 have been preliminarily demonstrated by in vitro assays. The results demonstrated that most of these compounds obtained by this protocol showed comparable or even much better activity than the positive control of cisplatin. GRAPHICAL ABSTRACT

Alcohols as Substrates and Solvents for the Construction of 3-Alkoxylated-2-Oxindoles by Direct Alkoxylation of 3-Halooxindoles

Described herein is an environmentally benign method for the synthesis of multisubstituted 3-alkoxylated-2-oxindoles 3 via direct alkoxylation of 3-halooxindoles 1. A wide variety of such multisubstituted 3-alkoxylated-2-oxindole scaffolds were smoothly obtained in good yields (up to 94%) by heating in an oil bath at 35 °C for 24 h. A particularly valuable feature of this method was the development of environment-friendly chemistry using alcohols 2 as both the substrates and solvents in the presence of a catalytic amount of base.

Efficient 1,6-addition reactions of 3-substituted oxindoles: Access to isoxazole-fused 3,3′-disubstituted oxindole scaffolds and hexahydro-1h-pyrido[2,3-b]indol-2-one scaffolds

ABSTRACT Developed herein is a new methodology for a hybrid of two pharmacophoric oxindole and isoxazole motifs to construct isoxazole-fused 3,3′-disubstituted oxindole scaffolds via an efficient 1,6-addition reaction of 3-substituted oxindoles to 3-methyl-4-nitro-5-alkenylisoxazoles, which might generate novel drug-like molecules for biological screenings. The method gives an easy access to a series of isoxazole-fused 3,3′-disubstituted oxindoles with 26 examples in high yields (up to 92% yield) and good diastereoselectivity (up to >20:1), which makes possible the synthesis of libraries under similar circumstances. Subsequently, a sequential Michael addition/amidation/reductive cyclization process was designed for accessing this hexahydro-1H-pyrido[2,3-b]indol-2-one scaffold, which is a key structural skeleton found in a large number of biologically active natural products and pharmaceutical compounds. Hexahydro-1H-pyrido[2,3-b]indol-2-one scaffold 7cg could be obtained in 42.5% overall yield after 4 steps. GRAPHICAL ABSTRACT

Molecular hybridization-guided annulation reactions of isatins with 4-methylpent-3-en-2-one: A direct access to spirooxindole tetrahydropyranones

ABSTRACT An efficient molecular hybridization strategy has been utilized for the synthesis of pirooxindole tetrahydropyranones 3 through annulation reactions of isatins 1 with 4-methylpent-3-en-2-one 2. Products consist of a pirooxindole tetrahydropyranone scaffold and propan-2-ether unit were smoothly obtained in moderate yields (up to 56% yield). The one-pot, two-step reaction, avoiding the isolation and purification of intermediates C, has proved to be a practical protocol. This protocol leads to new knowledge in the fields of both molecular complexity and the lead compound discovery. GRAPHICAL ABSTRACT

Molecular hybridization-guided one-pot multicomponent synthesis of chromanone-fused 3,3′-pyrrolidinyl-dispirooxindoles through a 1,3-dipolar cycloaddition reaction

ABSTRACT A new methodology was developed for the synthesis of 3,3′-pyrrolidinyl-dispirooxindoles 3 through a 1,3-dipolar cycloaddition event of isatylidenyl-chromanones 2 with azomethine ylides (thermally generated in situ from isatins and sarcosine). The method gives an easy access to a series of highly functionalized products containing three consecutive stereocenters and vicinal spiroquaternary stereocenters fused in one ring structure with 15 examples in high yields (up to 82% yield) and good diastereoselectivity (up to >20:1), which makes possible the synthesis of libraries under similar circumstances. Moreover, the current method provides a convenient approach for the efficient incorporation of two biologically important scaffolds (chromanone and 3,3′-pyrrolidinyl-dispirooxindoles). X-ray diffraction studies of one of the cycloadducts proved the structure and regiochemistry of the cycloaddition. In particular, their biological activity against human leukemia cells K562 and normal L929 cells has been evaluated. These results suggested that 3,3′-pyrrolidinyl-dispirooxindoles 3 may be potential leads for further biological screenings. GRAPHICAL ABSTRACT

Diversity-oriented regioselective domino Michael/Aldol reaction of 3-ylideneoxindoles: A direct access to indanol-fused 3-oxindoles

ABSTRACT A diversity-oriented molecular hybridization strategy has been utilized for the synthesis of 2,3-disubstituted 1-indanol-fused 3-oxindoles through a regioselective domino Michael/Aldol reaction of 3-ylideneoxindoles 1 with malononitrile or cyanacetate ethyle 2. Products bearing consecutive stereocenters consist of an oxindole moiety and an indanol core, were smoothly obtained in high yields (up to 92% yield) with good diastereoselectivity (up to 20:1). This protocol also represents the first construction of indanol-fused 3-oxindole scaffolds, thus leading to new knowledge in the fields of both molecular complexity and diversity-oriented synthesis (DOS) and the lead compound discovery. It is also worth mentioning that the reaction was completely regioselective and the competitive regioisomeric products 4 or 5 were not obtained in any case. GRAPHICAL ABSTRACT

Diversity-oriented TsOH catalysis-enabled construction of tanshinone-substituted bis(indolyl/pyrrolyl)methanes and their biological evaluation for anticancer activities

ABSTRACT We have developed an efficient and straightforward methodology for the synthesis of novel tanshinone-substituted bis(indolyl/pyrrolyl)methane scaffolds 3 through TsOH catalysis-enabled addition of indoles or pyrroles 1 with tanshinones 2 based on molecular hybridization strategy. Products were smoothly obtained in good yields (up to 81% yield). This protocol also represents the first construction of tanshinone skeleton-fused bis(indolyl/pyrrolyl)methane scaffolds, thus leading to new knowledge in the fields of both molecular complexity and diversity-oriented synthesis and the lead compound discovery. Furthermore, their biological activities against human leukemia cells K562, human prostate cancer cells PC-3, and human lung cancer cells A549 have been preliminarily demonstrated by in vitro assays. The results demonstrated that most of these compounds 3 obtained by this protocol showed comparable activity to the positive control of cisplatin. GRAPHICAL ABSTRACT

Rapid, microwave-accelerated synthesis and anti-osteoporosis activities evaluation of Morusin scaffolds and Morusignin L scaffolds

Described herein is a facile and efficient methodology toward the synthesis of Morusin scaffolds and Morusignin L scaffolds 4-9 and 12via a novel three-step approach (Michael addition or prenylation, cyclization and cyclization) and use a rapid, microwave-accelerated cyclization as the key step. Furthermore, their biological activities have been preliminarily demonstrated by in vitro evaluation for anti-osteoporosis activity. These Morusin, Morusignin L and newly synthesized compounds 5b, 6a, 8e, 8f greatly exhibited the highest potency, especially at the 10-5mol/L (P<0.01), and had good in vitro anti-osteoporosis activities using the commercially available standard drug Ipriflavone as a positive control. The mechanisms associated with anti-osteoporosis effects of these compounds may be through the inhibition of TRAP enzyme activity and bone resorption in osteoclasts, and promotion effect of osteoblast proliferation in vitro. The results indicated that Morusin scaffolds and Morusignin L scaffolds may be useful leads for further anti-osteoporosis activity screenings.