A new short strategy to prepare the spiroketal fragment of calyculins is presented. A novel Seyferth–Gilbert type homologation of hindered lactols to the corresponding alkynes has been achieved for the first time. The spirocyclization was achieved efficiently via a DIHMA (double intramolecular hetero-Michael addition) process of this hindered ynone. The spirocyclization rate is not dependent on...

An efficient synthesis of novel 2,3-dihydro-4H-pyrido[1,2-a]pyrimidin-4-ones has been reported. Inexpensive and readily available substrates, environmentally benign reaction condition, and product formation up to quantitative yield are the key features of this methodology. Products are formed by the aza-Michael addition followed by intramolecular acyl substitution in a domino process. The polar...

Four fluorescent non-natural aromatic amino acids have been synthesized based on a key stereoselective Michael addition reaction. S-1-phenylethylamine was employed as both the source of amine and the stereoselectivity controller. The overall yields were moderate (30-50%). Fluorescent properties of some of the fluorophores were also investigated. It was found that compounds with a dimethylamino ...

Herein, we disclose a general and flexible access to spirocyclopropyl oxindoles by a domino Michael/intramolecular nucleophilic substitution pathway with variously substituted vinyl selenones and enolizable oxindoles in aqueous sodium hydroxide solution. The spirocyclopropyl oxindole being a privileged scaffold, some of the synthesized compounds were selected for biological evaluation. Compound...

An asymmetric synthesis of the C(9)-C(25) spiroketal fragment of calyculin C is described. Key steps include two crotylation reactions using successively Brown's reagent and (Z)-crotyltrifluorosilane for the formation of the anti, anti, anti stereotetrad, ynone formation by a Pd-catalyzed coupling of a thiol ester with a terminal alkyne and a double intramolecular hetero-Michael addition for th...

The enantioselective syntheses of deoxydihydrokalafungin (5), cis-deoxydihydrokalafungin (6) and deoxykalafungin (7) are reported. The strategy was based on 4 key reactions: (1) CBS reduction of prochiral ketone 10 to introduce chirality at C-1, (2) radical allylation of quinone 9a, (3) cross-metathesis of dimethoxynaphthalene 13 with methyl acrylate, and (4) intramolecular oxa-Michael addition...

Cyclic peptide architectures can be easily synthesized from cysteine-containing peptides with appending maleimides, free or protected, through an intramolecular Michael-type reaction. After peptide assembly, the peptide can cyclize either during the trifluoroacetic acid treatment, if the maleimide is not protected, or upon deprotection of the maleimide. The combination of free and protected mal...

We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the ...

An efficient synthesis of the N-methylwelwistatin tetracyclic core in only two steps from Kornfeld's ketone is described, whose key transformation involves the generation of a fused bicyclo[4.3.1]decane ring system through a one-pot sequence comprising a Michael-intramolecular aldolization anionic domino process and a DBU-promoted hydrolysis of the N-pivaloyl protecting group. Besides providing...

The development of new methods to skeletally diverse sultams based on a central α-halo benzene sulfonamide building block is reported. Several salient features of this building block are utilized in multiple reaction pathways, including the Heck reaction, C- and O-arylation, Sonogashira-Pauson-Khand, Sonogashira-intramolecular hydroamination, lithiative cyclization and domino aza-Michael Heck f...