Masaya Nakata

Enantiospecific Total Synthesis of a β-Glucosidase Inhibitor, Cyclophellitol

Abstract Cyclophellitol has been synthesized from L-glucose through an intramolecular cycloaddition of a nitrile oxide derived from an oxime.

Pigment chemistry: The red sweat of the hippopotamus

Within a few minutes of perspiration, the colourless, viscous sweat of the hippopotamus gradually turns red, and then brown as the pigment polymerizes. Here we isolate and characterize the pigments responsible for this colour reaction. The unstable red and orange pigments turn out to be non-benzenoid aromatic compounds that are unexpectedly acidic and have antibiotic as well as sunscreen activity.

Identification of the toxic trigger in mushroom poisoning

We have isolated the small, highly strained carboxylic acid cycloprop-2-ene carboxylic acid from the Asian toxic mushroom Russula subnigricans. This compound is responsible for fatal rhabdomyolysis, a new type of mushroom poisoning that is indicated by an increase in serum creatine phosphokinase activity in mice. We found that polymerization of the compound at high concentrations via ene reaction abolishes its toxicity.

Enantiospecific total synthesis of (-)-allosamizoline, and aminocyclitol moiety of the insect chitinase inhibitor allosamidin

Abstract Total synthesis of (−)-allosamizoline ( 2 ), an aminocyclitol moiety of the insect chitinase inhibitor allosamidin ( 1 ) has been enantiospecifically synthesized from D-glucosamine by using an intramolecular cycloaddition of the nitrile oxide to an olefin as a key step.

Total Synthesis of Herbimycin A

The first total synthesis of herbimycin A (1), the benzoquinoid ansamycin antibiotic, has been accomplished by coupling two segments of the aliphatic ansa-chain 2 and the aromatic chromophore 3, elucidating the absolute stereochemistry.

Total syntheses of glucosidase inhibitors, cyclophellitols

Abstract A β- d -glucosidase inhibitor, cyclophellitol [(1 S ,2 R ,3 S ,4 R ,5 R ,6 R )-5-hydroxymethyl-7-oxabicyclo[4.1.0]heptane-2,3,4-triol, 1 ] and its epoxide diastereomer, 1,6-epicyclophellitol ( 2 ) have been synthesized by using an intramolecular [3+2]-cycloaddition of a nitrile oxide to an alkene as a key step. 2,3,4-Tri- O -benzyl-6,7-dideoxy- d - ido -hept- 6-enose ( E,Z )-oxime ( 6 ) was prepared from l -glucose in 11 steps. Intramolecular cycloaddition of 6 was realized by NaOCl via an intermediary nitrile oxide to afford the isoxazoline, (1 S ,2 R ,3 S ,4 S ,5 R )-3,4,5-tribenzyloxy-2-hydroxy-8-oxa-7-azabicyclo[4.3.0]non-6-ene ( 7 ). Hydrogenolysis of 7 followed by a 5-step sequence gave cyclophellitol ( 1 ). Compound 2 was synthesized from methyl δ- d -galactopyranoside by using a conceptually similar route. The glycosidase-inhibiting activities of 2 were examined.

Total synthesis of methyl sarcophytoate, a marine natural biscembranoid.

The total synthesis of methyl sarcophytoate (1), a marine natural biscembranoid, has been achieved by the thermal Diels-Alder reaction between the 14-membered dienophile unit, methyl sarcoate (2), and the 14-membered diene unit 64. Methyl sarcoate (2) was prepared using n-BuLi-Bu(2)Mg-mediated dithiane coupling, Kosugi-Migita-Stille coupling, and Grubbs ring-closing metathesis. The diene unit 64 was prepared using Sharpless asymmetric epoxidation, Grubbs ring-closing metathesis, 6-exo-tet epoxide opening, and n-BuLi-Bu(2)Mg-mediated Ito-Kodama cyclization. The final Diels-Alder reaction between 2 and 64 proceeded with high site, endo/exo, pi-face, and regioselectivities. During this reaction, partial E --> Z isomerization at the C4 position was observed.

Absolute configuration and tautomeric structure of xylindein, a blue–green pigment of Chlorociboria species

The S absolute configuration of both chiral centers of xylindein was assigned using X-ray crystallographic heavy atom analysis after its conversion to a synthetic derivative. Crystallographic analysis of xylindein crystallized with phenols revealed that the proposed structure is the proper tautomer in the crystals.

Total synthesis of bafilomycin A1. 2. The assemblage and completion of the synthesis

Abstract The total synthesis of the macrolide antibiotic, bafilomycin A 1 ( 1 ), has been achieved by a convergent route involving aldol condensation between the 16-membered lactonic aldehyde 2 and the ethyl ketone 3 , followed by desilylation.

Total synthesis of kendomycin featuring intramolecular dötz benzannulation

One-step formation of the ansa-skeleton realized the synthesis of kendomycin, an ansa-type quinone methide. The Fischer carbene complex derived from the ansa-chain portion was subjected to the intramolecular Dotz benzannulation to afford the desired oxametacyclophane with exclusive regioselectivity. Subsequent Claisen rearrangement, ortho oxidation of the resulting phenol derivative, and mild transformation from p-quinone to p-quinone methide on a silica gel plate furnished kendomycin.