Jun-ichi Yamada

Aminolead compounds as a new reagent for regioselective ring opening of epoxides

Abstract Regioselective ring opening of epoxides is accomplished by using aminolead compounds; the reagents attack the less hindered carbon of epoxide ring, and the amino alcohols are obtained in good yields.

Stereocontrolled intramolecular cyclization of ω-tributylstannyl ether aldehydes. synthesis of the 6·7·7·6 ring system of polycyclic ethers

Abstract The BF 3 .OEt 2 mediated intramolecular cyclization of the γ-oxo-substituted allylic tin ( 1 ) having an aldehyde group at the terminus of the carbon chain proceeded in a stereocontrolled manner to give the 7-membered β-hydroxy cyclic ether ( 2a ) with high diastereoselectivity. This method was applied for the synthesis of the 6·7·7·6 ring system ( 3a ).

The alkylation of α-ethoxycarbamates with organo-lead, -zinc, and -copper reagents. High cram selectivity and formal nonbasic alkylation of imines

Abstract The alkylation of α-ethoxycarbamates is accomplished with organo-lead, -zinc, and -copper reagents in the presence of Lewis acids. The reaction proceeds with high diastereoselectivity in good to high yields.

Regioselective synthesis of either α- or γ- amino acid derivatives via Li, Sn-masked, and/or Ge-masked dienolates

Abstract Either the α- ( 3 ) or γ-amino acid derivatives ( 4 ) can be prepared with very high regioselectivity by treating diethyl azodicarboxylate (DEAD) with (i) lithium dienolates themselves ( 2 ) in certain cases, (ii) Sn-masked dienolates (5), or (iii) Ge-masked dienolates ( 6 ).

Rearrangement approaches to cyclic skeletons. V. : Formal bridgehead substitution of 1-methoxybicyclo[3.2.2]non-6-en-2-ones and its application to a total synthesis of (±)-widdrol

Abstract The C-1 methoxy group of bicyclo[3.2.2]non-6-en-2-ones is replaced by alkyl, alkenyl, and aryl groups or hydrogen with inversion of the absolute configuration via the two-step sequence consists of Grignard reaction or reduction of the carbonyl followed by pinacol-type rearrangement. This transformation was applied to the total synthesis of the [6-7] fused-ring sesquiterpene widdrol ((±)- 9 ). The stereochemistry of the tertiary alcohol of 9 was specifically controlled by employing a bridge-cleaving method.

Synthesis of a non-symmetric azodicarbonyl compound and its regioselective reaction with organometallic reagents

Abstract The non-symmetric azodicarbonyl compound 7 reacted with R-M/Lewis acid regioselectively at the nitrogen atom attached to the amide group giving 9 , whereas it reacted with R-M at the nitrogen atom attached to the ester group producing 8 in high yield.

Total synthesis of (±)-ptilocaulin starting from tropolone

A rearrangement approach to the antitumour antibiotic (±)-ptilicaulin was accomplished by photochemical [1,3]-acyl migration of 1-butyl-exo-8-methylbicyclo[3.2.2]non-6-en-2-one, derived from 1-methoxy-exo-3-methylbicyclo[3.2.2]non-6-en-2-one via the pinacol-type rearrangement, to give the [5–6] fusedring skeleton.

Total synthesis of (±) - isosesquicarene: A structural revision

Abstract We disclose the first total synthesis of (±) - isosesquicarene, the stereostructure of which has been revised consequently.

Regiocontrolled conjugate addition of germanium-masked dienolates to Michael acceptors

Abstract The reaction of Ge-masked dienolates with Michael acceptors in the presence of Lewis acids produced the 1,4-γ adduct regioselectively, whereas the reaction in the presence of Bu4NF gave the 1,4-α adduct exclusively.

Rearrangement approach to the formal displacement of the bridgehead methoxyl group of bicyclo[3.2.2]non-6-en-2-ones with alkyl alkenyl and aryl groups

Abstract A preferential trasformation of the C 2 -substituted 1-methoxybicyclo[3.2.2]non-6-en-2-ols, derived from 1-methoxybicyclo[3.2.2]non-6-en-2-ones, into the C 1 -substituted bicyclo[3.2.2]non-6-en-2-ones was accomplished by utilizing TsOH in toluene (85°C) or boiling benzene.