Susumu Ohira

Methanolysis of Dimethyl (1-Diazo-2-oxopropyl) Phosphonate: Generation of Dimethyl (Diazomethyl) Phosphonate and Reaction with Carbonyl Compounds

Abstract Dimethyl (1-diazo-2-oxopropyl) phosphonate (3) was transformed to dimethyl (diazomethyl)—phosphonate (4), which was used for the synthesis of enol ether or alkyne without isolation.

Sesquiterpenoids from Cyperus rotundus

Abstract New sesquiterpenoids with 4,5-secoeudesmane and cyperolone carbon skeletons were isolated from Cyperus rotundus , and characterized by spectroscopic analysis. The structures were confirmed by synthesis from (+)-dihydrocarvone and (+)-cyperolone.

Synthesis of (−)-neplanocin Avia C-H insertion of alkylidenecarbene

Abstract (−)-Neplanocin A, a naturally occurring carbocyclic nucleoside was synthesized via C-H insertion reaction of the alkylidenecarbene, which was generated by the reaction of lithiotrimethylsilyldiazomethane and the ketone derived from D-ribose.

C-H insertion method for the chiral tertiary alcohol: formal synthesis of (-)-frontalin.

Abstract Intramolecular insertion of the alkylidene carbene into CH bond adjacent to the protected secondary hydroxyl group gave a chiral tertiary alcohol derivative, which was converted to a synthetic intermediate of (−)-frontalin.

Total synthesis of sporochnols, fish deterrents from a marine alga

Abstract Sporochnols, fish deterrents from a marine alga, were synthesized, using intramolecular CH insertion of alkylidenecarbene as a key step to construct the chiral quaternary center.

Synthesis of tertiary alcohol from secondary alcohol via intramolecular CH insertion of alkylidenecarbene

Abstract Alkylidenecarbene generated by the reaction of dimethyl (diazomethyl)phosphonate and pyruvate did not render a 1,5 CH insertion, but gave an unusual product. In contrast, 2-oxopropyl ether was cleanly transformed into a cyclized product, from which functionalized tertiary alcohol was derived.

Enantioselective construction of alicyclic bicyclo[3.1.0]hexane framework by double stereodifferentiation and its application for the synthesis of both enantiomers of vitamin D3 CD ring synthons

Abstract Good diastereoselectivity (85:15) was observed in the intramolecular cyclopropanation of the chiral unsaturated α-diazo-β-keto ester 9f , which possesses ( R )-pantolactone as a chiral auxiliary. The reaction was catalyzed by a chiral bis-oxazoline copper ( l ) complex 17 . The absolute stereochemistry of each generated diastereomer ( 10f and 11f ) was elucidated. Both enantiomers of the vitamin D 3 CD ring synthons ((−)- 21 and (+)- 22 ) were synthesized from (−)- 12 and (+)- 13 , respectively.

Generation of α-alkoxycarbonyl alkylidenecarbenes: Synthesis of t-butyl cyclopentenecarboxylates

Abstract Triflates of 2-hydroxymethytene t-butyl esters, derived from simple t-butyl esters, were treated with potassium t-butoxide in THF to generate alkylidenecarbenes. At room temperature, they underwent intramolecular 1,5 C-H insertion giving t-butyl cyclopentenecarboxylates.

CONFIGULATION AT C-23 IN 5β-CHOLESTANE-3α, 7α, 12α, 23-TETROL EXCRETED BY PATIENTS WITH CEREBROTENDINOUS XANTHOMATOSIS

The configuration at C-23 in 5β-cholestane-3α, 7α, 12α, 23-tetrol, one of the bile alcohols isolated from the bile and feces of patients with cerebrotendinous xanthomatosis, has been determined by X-ray crystallography to be 23R.

Stereoselective Synthesis of (1S,3R)-1-Aminocyclopentane-1,3-dicarboxylic Acid via C–H Insertion of Alkylidenecarbene

(1S,3R)-1-Aminocyclopentane-1,3-dicarboxylic acid (ACPD), a potent agonist of metabotropic glutamate receptors, was synthesized from L-serine. The chiral quaternary center was constructed by C–H insertion of the alkylidenecarbene, this being generated by the reaction between lithiotrimethylsilyldiazomethane and the corresponding ketone.