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4-[((3,4-Dihydroxybenzoyl)oxy)methyl]phenyl β-D-glucopyranoside (DBPG, 1), a polyphenolic glycoside previously isolated from oregano (Origanum vulgare L.) in 0.08% isolated yield, was synthesized in five chemical steps with 41.4% overall yield. First, 4-(hydroxymethyl)phenyl -D-glucopyranoside 2,3,4,6-tetraacetate (4) was obtained in 53.2% yield by selective glycosylation of 4-hydroxybenzyl alcohol (3) with 2,3,4,6-tetra-O-acetyl-α-D- -glucopyranosyl bromide (2) in a mixture of chlorobenzene and aqueous CsOH using triethylbenzylammonium chloride (TEBAC) as a phase transfer catalyst. Then, this product was esterified with 3,4-diacetoxybenzoyl chloride (7) to generate 4-[((3,4-diacetoxybenzoyl)oxy)methyl]phenyl -D-glucopyranoside 2,3,4,6-tetraacetate (8) in 95% yield. Finally, selectively global deacetylation of 8 was performed in a mixture of dibutyltin oxide and methanol under reflux to afford 1 in 94.8% yield. [ABSTRACT FROM AUTHOR]

The use of dibutylstannylene ketals of two polyhydric alcohols is explored with the aim at the regiospecific preparation of partially esterified glycerol and meso-erythritol. The mono-dibutylstannylene ketal of glycerol with palmitoyl chloride gave both 1,3-diglyceride and 1-monoglyceride. The mono- and the bis-dibutylstannylene ketals of meso-erythritol with palmitoyl chloride under 1 : 1 and 1 : 2 mole ratios, respectively, gave the same product, 1,2,4-tripalmitoyl-meso-erythritol, while the bis-dibutylstannylene ketal of meso-erythritol and palmitoyl chloride (1 : 1 mole ratio) gave tri- and di-esters of meso-erythritol. The probable paths to these products are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The reaction process for the selective deprotection of acetylated glucosides by dibutyltin oxide in methanol is investigated by using methyl 2,3,4,6-tetra-O-acetyl-α-d-glucopyranoside as a model substrate with ESIMS and NMR techniques. According to the results, it is inferred that at first, dimeric 1,3-dimethoxytetrabutyldistannoxane is formed by the reaction of dibutyltin oxide with methanol, and then the tetraorganodistannoxane reacts with the acetylated glucoside to produce glucoside–organotin complex intermediates. Finally, the complex intermediates are hydrolyzed leading to the free-OH glucoside and organotin acetate derivatives. The reaction is affected by neighboring group participation and steric hindrance, which allow for high selectivities among different acetyl groups in acetylated glucosides. [ABSTRACT FROM AUTHOR]

Abstract: Glycerophosphorylcholine (GPC) is transformed into the cyclic stannylene derivatives, which are selectively acylated to 1-acyl-2-lyso-glycerophosphocholines. The reaction is effective using C-2 to C-16 acid chlorides in 2-propanol. After solvent replacement the lyso-phospholipid (lyso-PL) is subjected to a second acylation using acid anhydrides in methylene chloride. A series of 1(2)-short-2(1)-long-diacyl-glycerophosphocholines are obtained in high yields and selectivity. No diacylation product was detected. In order to detect mixed-chain lipids with inverted disposition of acyl chains, the long chain was introduced first and the thus resulting isomeric compounds compared by NMR. An NMR method was developed in order to determine the positional purity of the isomeric compounds. [Copyright &y& Elsevier]

Abstract: Dibutyltin oxide (DBTO) was first utilized for the deacetylation of steroid and diterpene esters. The results showed the deprotection of acetylated steroids and diterpenes separately with moderate catalysis dibutyltin oxide in methanol selectively removed part acetyl groups of these substrates, whereas several functional groups of the steroids and diterpenes were retained and neither isomerization nor degradation of these substrates was observed. It seems that the acetyl groups with lower steric hindrance or near carbonyl, alkoxy, or hydroxyl groups can be cleaved by the reaction, whereas the acetyl groups with higher steric hindrance or without carbonyl, alkoxy, or hydroxyl groups neighboring were retained under the same conditions. One of the interesting results obtained was the selective hydrolysis of the 3β-O-acetyl group in the presence of the 6β group in 3β,6β-Di-O-acetyl-5α-hydroxypregn-16-en-20-one. This allows for subsequent introduction of one unit at C-3 and the other unit at C-6. This procedure is useful for the synthesis of a series of closely related isomers of 3β,5α,6β-trihydroxypregn-16-en-20-one and other widespread polyhydroxysteroids in marine organisms and some terrestrial species. [Copyright &y& Elsevier]

Abstract: The synthesis of monomer, dimer, tricyclohexyl- and triphenyl-tin(IV) complexes with phthalimido-4-methyl pentanoic acid (PMPA) are described and characterized by FT IR, CHN analyzer, 1H, 13C 119Sn NMR and 119mSn Mössbauer spectroscopic techniques. In vitro ED50, anti-tumor (phytotoxic), anti-yeast, blood pressure and heart rate effect, and bactericidal, fungicidal as well as analgesic bioassays of complexes are also be carried out. The ligand (PMPA) shows excellent analgesic activity while the dimer exhibit strong biocidal and excellent anti-tumor behavior besides of tri-organotin(IV) complexes. [Copyright &y& Elsevier]

Depolymerization of poly(ethylene terephthalate) (PET) was performed in the tubular bomb microreactor which contained the solution of PET in methanol and dibutyltin oxide at the temperature ranging from 433 K to 473 K, the reaction time from 5 to 45 min and the catalyst-to-PET ratio of 0.3%–2% by weight. The optimal condition for PET depolymerization catalyzed by dibutyltin oxide is the temperature of 443–453 K, the reaction time of 20–25 min and 0.8% by weight of catalyst. By using differential methods, the activation energy for the depolymerization process was found to be 154.05 kJ/mol in the temperature range from 433–463 K. [ABSTRACT FROM AUTHOR]

A new protocol has been developed for the generation of alkylidenecarbene derivatives of monosaccharides based on the reaction of trimethylsilylazide and Bu 2 SnO with α‐cyanomesylates derived from uloses. When this method is applied to conveniently functionalized carbohydrate derivatives it provides novel heterocyclic ring systems by the rare 1,6‐C‐H or 1,5‐O‐Si insertion reactions. [ABSTRACT FROM AUTHOR]

Acetylated 3β-O-β-glycosyl steroid derivatives were synthesized by the reaction of a new polyhydroxysteroid 3β,5α,6β-trihydroxypregn-16-en-20-one (2) with the peracetylated 1-bromo derivatives of d-glucose and d-galactose, respectively. Subsequent protection by excess acetic anhydride in pyridine selectively gave the 6β-O-acetylated steroid glycosides. Deprotection of the acetylated steroid glycosides separately with moderate catalysis dibutyltin oxide in methanol selectively removed all acetyl groups of sugar moiety, whereas the acetyl group of the steroid part was retained. The structures of the steroid glycosides were confirmed by mass spectrometry, NMR and IR. The complete protocol was shown to be non-destructive at all stages to the sugar moieties and the steroid nucleus. These regioselective reactions open a route to the synthesis of a series of closely related isomers of 2 and other widespread polyhydroxysteroids and steroid glycosides in marine organisms and some terrestrial species. [Copyright &y& Elsevier]

A new facile method for monoesterification of diols has been developed. A variety of diols, in particular oligoethylene glycols, were selectively monoesterified in excellent yields by reaction with aromatic and aliphatic acids in the presence of Al2O3/MeSO3H as a new reagent without use of any solvents. [Copyright &y& Elsevier]

A mild and efficient neutral method for the cleavage of O-acetyl groups with dibutyltin oxide has been developed. This method is especially useful in the synthesis of glycosides containing base- or acid-sensitive multifunctional groups. [Copyright &y& Elsevier]

β-Nitro alcohols (nitro aldols) in boiling benzene in the presence of Bu2SnO (20-30 mol.%) under neutral conditions undergo dehydration leading to nitroalkenes. [ABSTRACT FROM AUTHOR]