Total synthesis of (+)-macbecin I

Abstract

t This approach had been previously used to prepare (E)-3-chloro-and (E)-3-bromo-2-methylprop-2-enoic acids. t9-BBN-OTf = 9-borabicycloC3.3. llnonyl trifluoromethanesulphonate, TBDMS-OTf = t-butyldimethylsilyl trifluoromethanesulphonate.

Improvement of Fluorescence Characteristics of Coumarins: Syntheses and Fluorescence Properties of 6-Methoxycoumarin and Benzocoumarin Derivatives as Novel Fluorophores Emitting in the Longer Wavelength Region and Their Application to Analytical Reagents

“…30) Other derivatives 1b-f, with various substituents at the 3-position, were synthesized from 5-methoxysalicylaldehyde 31) with active methylene compounds such as ethyl acetoacetate, diethyl malonate, ethyl cyanoacetate, and ethyl nitroacetate by means of Knoevenagel condensation 32) using piperidine as a catalyst in dry ethanol, and with phosphoranes such as carbethoxymethyl triphenylphosphorane and carbethoxyethyllidene triphenylphosphorane in diethylaniline, respectively. The benzocoumarin derivatives 4a and b, 5a and b, and 6a-d and f were also obtained from the appropriate hydroxynaphthaldehyde in a similar manner to that for 6-methoxycoumarin derivatives.…”

“…This compound was prepared from 5-methoxysalicylaldehyde 31) and calbethoxyethylidene triphenylphosphorane in diethylaniline according to the method described in a literature. 30) Crude product was subjected to silica gel chromatography using chloroform as the eluent and recrystallized from hexane to give 1b as pale yellow needles.…”

Regio- and Stereoselective Synthesis of 2,3,5-Trienoates by Palladium-Catalyzed Alkoxycarbonylation of Conjugated Enyne Carbonates

“…The product diethyl 2-(diiodomethyl)-2-methylmalonate (S9) was purified by distillation at 130°C and 12 bar (yield = 14.3 g, 65%). 32 The solution of S9 (∼33 mmol) and KOH (5.6 g, 0.1 mol) in EtOH/H 2 O (3:1, 45 mL) was refluxed for 24 h and cooled to room temperature. The reaction mixture was concentrated under reduced pressure, diluted with an aqueous solution of K 2 CO 3 (27 mL, %10), and washed with dichloromethane (2 × 9 mL).…”

“…(E)-3-Iodo-2-methylacrylic acid (S10) was purified from the residue by crystallization with petroleum ether (yield = 12.9 g 89%). 32 Lithium aluminum hydride (1.1 g, 29 mmol) was slowly added to the solution of S10 (∼29 mmol) in 48 mL of dry THF at 0°C temperature under Ar. The reaction mixture was allowed to warm to room temperature and stirred for 3 h. The reaction mixture was recooled to 0°C and quenched with saturated aqueous Na 2 SO 4 by dropwise addition.…”

First Synthesis of a Series of New Natural Glucosides

“…11 According to the Reimer-Teimann reaction, treatment of 13 with NaOH solution in CHCl 3 gave 2-hydroxy-5-methoxybenzaldehyde (14) in 48% yield. 12 Wittig reaction of benzaldehyde 14 with Ph 3 P ＋ CH 2 CH 3 Br -in the presence of t-BuOK in THF gave a mixture of E-and Z-configuration alkene, 8 followed by a transformation in the presence of I 2 to afford 4-methoxy-2-[(E)-1-propenyl]phenol (15) in 86% overall yield for two steps. 13 For the preparation of last aglycon, treament of 16 with dimethyl sulfate (Me 2 SO 4 ) gave methyl 3,4,5-trimethoxybenzoate (17), which was refluxed in piperidine for 48 h to afford methyl 4-hydroxy-3,5-dimethoxybenzoate (18) in 77% overall yield for two steps.…”