Highly diastereoselective entry to chiral oxindole-based β-amino boronic acids and spiro derivatives

We here describe the first Cu-catalysed, diastereoselective 1,2-addition of 1,1-diborylmethane to chiral ketimines for the synthesis of quaternary stereocenters and spiro compounds. The method provides easy access to a range...

Rearrangement of substituted pyrimidin-4-ones under the Vilsmeier-Haack reaction

The article describes the result of our study on rearrangements of four heterocyclic systems with variation of oxygen and nitrogen atoms, in particular, the results of formylation of 2,2-disubstituted hydroquinazolones under the conditions of the Vilsmeier-Haack reaction. A new rearrangement of spiro derivatives of quinazolin-4(3H)-ones was discovered under the action of a formylating reagent with the formation of predicted 1-cyclohex(pent)-1-en-1-ylchinazolin-4-(1H)-ones. The absence of this rearrangement for 2,2-dimethyl-2,3-dihydroquinazolin-4(1H)-one is explained. 6',7',7'-Trimethyl-1',5',6',7'-tetrahydrospiro [cyclohexane-1,2'-pyrrolo[3,4-d]pyrimidine]-4'(3'H)-one is a structural analogue of spiro derivatives of quinazolin-4(3H)-ones; it undergoes a similar rearrangement with the formation of 1-cyclopent-1-en-1-yl-6,7,7-trimethyl-1,5,6,7-tetrahydro-4H-pyrrolo[3,4-d]pyrimidin-4-one when interacting with Vilsmeier-Haack reagent.

Synthesis of Spiro-Isoxazolidine Derivatives of Methyl α-Isocostate

Background: In recent decades, natural products are an important source of chemotherapeutics as more than half of the effective cancer drugs can be traced to natural origins. Objective: Moreover, the modification of natural products is one of the most common and fruitful approaches to obtain novel therapeutic agents in medicinal chemistry. Method: Continuing with a research project based on the support of Moroccan plant resources. we report herein the use of α-isocostic acid extracted in enantiomerically pure form from Dittrichia viscosa as a convenient starting material for the synthesis of new eudesmane derivatives. Results: Novel spiro derivatives with a natural scaffold were prepared. Spiro-isoxazolidine derivatives were generated on the exocyclic double bond adjacent to the ester α,β-unsaturated function by 1,3-dipolar cycloaddition of methyl α-isocostate 1 derived from sesquiterpenic isocostic acid, with nitrones 2. Conclusion: This procedure allowed us to generate enantiomerically pure spiro compounds in one diastereoisomer form with a limited number of steps. These compounds were fully characterized by spectroscopic methods.

The crystal structures and Hirshfeld surface analysis of 6-(naphthalen-1-yl)-6a-nitro-6,6a,6b,7,9,11a-hexahydrospiro[chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazole-11,11′-indeno[1,2-b]quinoxaline] and 6′-(naphthalen-1-yl)-6a′-nitro-6′,6a′,6b′,7′,8′,9′,10′,12a′-octahydro-2H-spiro[acenaphthylene-1,12′-chromeno[3,4-a]indolizin]-2-one

The title compounds, 6-(naphthalen-1-yl)-6a-nitro-6,6a,6 b,7,9,11a-hexahydrospiro[chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazole-11,11′-indeno[1,2-b]quinoxaline], C37H26N4O3S, (I), and 6′-(naphthalen-1-yl)-6a′-nitro-6′,6a′,6b′,7′,8′,9′,10′,12a′-octahydro-2H-spiro[acenaphthylene-1,12′-chromeno[3,4-a]indolizin]-2-one, C36H28N2O4, (II), are new spiro derivatives, in which both the pyrrolidine rings adopt twisted conformations. In (I), the five-membered thiazole ring adopts an envelope conformation, while the eight-membered pyrrolidine-thiazole ring adopts a boat conformation. An intramolecular C—H...N hydrogen bond occurs, involving a C atom of the pyran ring and an N atom of the pyrazine ring. In (II), the six-membered piperidine ring adopts a chair conformation. An intramolecular C—H...O hydrogen bond occurs, involving a C atom of the pyrrolidine ring and the keto O atom. For both compounds, the crystal structure is stabilized by intermolecular C—H...O hydrogen bonds. In (I), the C—H...O hydrogen bonds link adjacent molecules, forming R 2 2(16) loops propagating along the b-axis direction, while in (II) they form zigzag chains along the b-axis direction. In both compounds, C—H...π interactions help to consolidate the structure, but no significant π–π interactions with centroid–centroid distances of less than 4 Å are observed.