Kazuishi Makino

Efficient enantioselective synthesis of (2R,3R)- and (2S,3S)-3-hydroxyleucines and their diastereomers through dynamic kinetic resolution

Abstract (2R,3R)- and (2S,3S)-3-Hydroxyleucines, components of cyclodepsipeptides, papuamides and polyoxypeptins, were efficiently synthesized along with their diastereomers from the corresponding β-keto-α-amino acid ester through dynamic kinetic resolution using RuCl2(binap)-catalyzed hydrogenation.

Stereoselective synthesis of (3S,4R)-3,4-dimethyl-(S)-glutamine and the absolute stereochemistry of the natural product from papuamides and callipeltin

Abstract (3S,4R)-3,4-Dimethyl-(S)-glutamine, a common component of cyclodepsipeptides, papuamide A and callipeltin A, was stereoselectively prepared from (S)-pyroglutamic acid. The stereostructure of natural dimethylglutamine was unambiguously confirmed to be (2S,3S,4R) by comparison of the CD and NMR spectra of the synthetic 3,4-dimethylpyroglutamic acid with the hydrolysate of callipeltin A.

Stereoselective synthesis of (S)-(+)-lycoperdic acid through an endo selective hydroxylation of the chiral bicyclic lactam enolate with MoOPH

Abstract Efficient synthesis of (S)-(+)-lycoperdic acid has been achieved by use of the stereoselective hydroxylation of the enolate derived from the bicyclic lactam 3 with the molybdenum oxidizing reagent, MoOPH (MoO5·Py·HMPA, oxodiperoxymolybdenum(pyridine)(hexamethylphosphoric triamide)), as a key step.

Synthetic studies on polyoxypeptins: stereoselective synthesis of (2S,3R)-3-hydroxy-3-methylproline using SmI2-mediated cyclization

Abstract Stereoselective synthesis of (2 S ,3 R )-3-hydroxy-3-methylproline ( 3 ), a component of polyoxypeptins, has been achieved by use of SmI 2 -mediated diastereoselective cyclization reaction as a key step.

Remarkable endo selectivity on hydroxylation of bicyclic lactam enolates with MoOPD and MoOPH

Remarkable endo selectivity was observed during the hydroxylation of the enolates derived from the bicyclic lactam 1a and its relatives with molybdenum oxidizing reagents, MoOPD and MoOPH, showing that the molybdenum reagents approach the enolate from the sterically hindered concave face of the lactam in spite of their bulkiness.

Synthesis of the acyl side chain segment of polyoxypeptins using regioselective ring-opening of chiral 2,3-epoxy alcohol

(2S,3R)-3-hydroxy-3-methylproline ones. The intriguing biological activities coupled with the unique structure of polyoxypeptins prompted us to synthesize these novel cyclodepsipetides. As studies directed towards the total synthesis of the polyoxypeptins, we have already reported efficient synthesis of (2S,3S)-3hydroxyleucine 2a using dynamic kinetic resolution and (2S,3R)-3-hydroxy-3-methylproline using SmI2-mediated cyclization. 2f We describe here stereoselective synthesis of the acyl side chain segment 2 from chiral 2,3-epoxy alcohol 6, easily prepared by Sharpless asymmetric epoxidation, through a regioselective ring-opening reaction. Kobayashi and Kurosu have indepen

Palladium-catalyzed asymmetric intramolecular metallo-ene reaction using monodentate phosphines, 9-PBN and 9-NapBN

The palladium-catalyzed asymmetric intramolecular metallo-ene reaction of the type I substrate using 9-PBN and 9-NapBN smoothly takes place in the presence of B(OAc) 3 and/or NaBF 4 at room temperature to afford the products with up to 51%ee, the best value in this area.

Synthesis of New Chiral Bis-oxazoline Ligand with Zinc Triflate-Selective Chelating Ability and Its Applications

New chiral bis-oxazoline ligand (10) with a dihydroanthracene skeleton was synthesized and its application to enantioselective Diels-Alder reaction and Henry reaction has revealed extremely zinc triflate-selective chelating ability of 10.

Synthesis of Bisdesmosidic Oleanolic Acid Saponins via a Glycosylation-Deprotection Sequence under Continuous Microfluidic/Batch Conditions

We report the first synthesis of a series of bisdesmosidic oleanolic acid saponins using microflow reactor Comet X-01 via a continuous flow glycosylation-batch deprotection sequence. The main results of this study can be summarized as follows: (1) The microfluidic glycosylation of oleanolic acid at C-28 was achieved in quantitative yield and was applied to the synthesis of six C-28-monoglycosidic saponins. (2) The microfluidic glycosylation of oleanolic acid at C-3 was achieved in good yield without orthoester byproduct formation and was applied to the synthesis of three bisdesmosidic saponins. (3) The continuous synthesis of saponins via a microfluidic glycosylation-batch deprotection sequence was achieved in four steps involving two purifications. Thus, the continuous microfluidic glycosylation-deprotection process is expected to be suitable for the preparation of a library of bisdesmosidic oleanolic acid saponins for in vivo pharmacological studies.