Dibutylstannylene derivatives

Figure 3 The dimeric structure of the dibutylstannylene derivative of methyl-4,6-di-O-benzylidene-a-D-glucopyranoside. " ...

The benzylidene derivative (94) has been converted into the alcohol (95) [97, 98] using the diborane — trimethylamine — aluminium chloride reagent [99] and into the diol (96) [95, 100, 101]. Veyrieres has converted methyl P-lactoside (and the corresponding allyl lactoside) into the 3-O-allyl ether (97) in good yield [102] by alkylation of the dibutylstannylene derivative in the presence of tetrabutylammonium iodide [103, 104], and this was converted into the alcohol (98) and the triol (99) [105]. Veyrieres [106] has also converted (97) into the per-p-bromobenzyl derivative and deallyl-ated the product to give a derivative with a free 3 -hydroxyl group. The diol (100) [107] has been converted by the stannylation procedure [108, 109] into the alcohol (101) [110, 111]. The partially acetylated benzyl P-lactoside (103) [101,112, 113] has been converted into the alcohol (104) via the orthoacetate [113]. 

The 8-methoxycarbonyloctyl derivative of lactose has been prepared from lactose octaacetate in the presence of tin(lV) chloride or from acetobromolactose in the presence of silver triflate [123,124] and converted into the derivative (108) with a free 4 -hydroxyl group [125] via the 4, 6 -0-benzylidene derivative. The benzyl lactoside (109) was converted into the benzyl ether (110) by the action of benzyl bromide and tetrabutylammonium bromide on the dibutylstannylene derivative [126] and this was converted into the benzoate (111). Phase transfer benzylation of the benzyl lactoside (112) has given the lactose derivative (113) with a free 3-hydroxyl group in 38% yield [118]. 1,6-Anhydrolactose has also been used for the preparation of the protected lactose derivative (114) [127]. 

The methyl 3 -0-allyl-P-lactoside (97) prepared by Veyrieres by the allylation of the dibutylstannylene derivative in the presence of tetrabutylammonium bromide [102] was converted into the per-p-bromobenzyl ether and deallylated to give (306). This was condensed "[106] with the chloride (282) in the presence of silver triflate to give a tetrasaccharide in 68 % yield. This was far superior to the condensation of the oxazoline (294) with (306) which gave a very low yield (9%) of tetrasaccharide. Depro-... 

Veyrieres et al. [102] also showed that allylation of the dibutylstannylene derivative of the lactosamine derivative (302) in the presence of tetrabutylammonium bromide gave the 3 -0-allyl ether in 56 % yield. 

Cyclic dibutylstannylene derivatives are formed when a suitable polyol is heated with an equimolar amount of dibutyltin oxide in methanol [128-130] or in benzene with azeotropic removal of water [58], Such a stannylation enhances the nucleophilicity of one of the bound oxygen atoms, so that a high yield of mono-benzylated products is obtained by the action of benzyl bromide either in DMF [58, 109, 124, 128-137] or by... 

Monoacylation of diols.1 Monoacylation of unsymmetrical 1,2-, 1,3-, and 1,4-diols can be effected by acylation of the dibutylstannylene derivatives, followed by quenching with oxalic acid or ClSi(CH3)2C6H5. This process effects monoacylation of the more-substituted hydroxyl group, even a tertiary one. This method also is... 

Cyclic dibutylstannylene derivatives are convenient intermediates for the regioselective benzylation of polyols.6 These derivatives can easily be prepared by reaction with Bu2SnO or Bu2Sn(OMe)2 with removal of water or methanol, respectively. They can be alkylated in benzene,... 

BIS(LAUROYLOXY)DI(n-BUTYL)STANNANE BUTYNORATE DBTL DIBUTYLBIS(LAUROYLO-XY)TIN DI-n-BUTYLTIN DipODECANOATE) DIBUTYLTIN DILAURATE (USDA) DIBUTYLTIN LAURATE DIBUTYL-ZINN-DILAURAT (GERMAN) FOMREZ SUL-4 LAUDRAN DI-n-BUTYLCINICITY (CZECH) LAURIC ACID, DIBUTYLSTANNYLENE derivative LAURIC ACID, DIBUTYLSTANNYLENE S.YLT... 

An improved synthesis of 2,4,6-tri-O-benzyl-D-galactopyranose has been accomplished by way of benzylation ofallyl 3-0-allyl-2,6-di-0-benzyl-a-D-galactopyrano-side, which was obtained by regiospecific allylation of the 3,4-0-dibutylstannylene derivative of allyl 2,6-di-O-benzyl-a-o-galactopyranoside (see Vol. 10, p. 122). 

A synthesis of 2 -0-methyluridine has been carried out by a procedure in which the 3, 5 -0-TIPDS derivative of uridine was protected at N-3 by the p-methoxybenzyl group,208 and the "wobble position" nucleoside 2 -0-methyl-5-(methoxycarboxylmethyl)uridine has also been prepared by similar means.209 The 2 -0-allyl derivative (141) of uridine is accessible by a palladium-catalysed decarboxylation of (142), and a similar reaction is possible on an adenosine derivative.210 2 -0-Propargyl uridine can be prepared via the 2, 3 -0-dibutylstannylene derivative the triple bond of this derivative could then be converted into an unusual carboranyl group, the resultant structure being of potential use in the neutron capture therapy of cancer.211 A conference report has discussed the use of 2-(methylthio)-phenylthiomethyl (MPTM) ethers for protection of the 2 -hydroxyl group in oligoribonucleotide synthesis.212... 

An a-lactosamine derivative has been synthesised (48% overall yield) in a similar reaction sequence. Oxidation (Br -BUgSnOMe - MeCN) of the dibutylstannylene derivative of methyl 3, 4 -Q-isopropylidene-a-lactoside led specifically to a 2-keto-... 

Oxidation of the dibutylstannylene derivative of methyl 3, 4 -0-isopropylidene-a-lactoside with bromine in acetonitrile in the presence of tributyltin methoxide led specifically to the 2-ketone isolated as its o-methyl or Q-benzyl oxime, whereas the corresponding 0-lactoside derivative gave the 3-ketone selectively. Microbial oxidation of toluene (using Pseudomonas putida 39D) gave the cis-diol (1), which after Q-protection and ozonolysis afforded the chiral pentosuloses (2). Photochemical... 

The lactone (25) of KDO was produced when benzylation of the 4.5-diol was carried out via the dibutylstannylene derivative a similar reaction on the 4,5-Q-isopropylidene - methyl ester -a-methyl glycoside gave the 8-Q-benzyl derivative with no 1.7-lactone formation.23... 

Methyl 4,6-0-benzylidene-a- and -jS-D-glucopyranosides and other sugars containing a vicinal trans-diol grouping reacted with dibutyltin oxide to give O-(dibutylstannylene) derivatives (see Vol. 8, p. 121),... 

Other Alkyl and Aryl Ethers. - The reagent system of allyl ethyl carbonate and a Pd(0) catalyst, applied to carbohydrate alcohols, has been utilised for making allyl ethers under neutral conditions. The synthesis of benzyl ethers from the parent alcohols under non-basic conditions has been achieved using phenyldiazomethane and HBF4. Dibutylstannylene compounds derived from benzyl -D-lactoside and its derivatives have been regioselectively benzylated. ° Similarly, 2,2 -di-0-alkyl-4,6 4 6 -di-0-benzylidene-Qt,a-trehaloses have been prepared by regioselective alkylation of a dibutylstannylene derivative. Phase transfer catalysed benzylation... 

The glycal diols (9) and (10) were selectively acetylated at 0-3 yja their dibutylstannylene derivates, and l,5-anhydro-4,6-0-benzylidene-D-galactitol(ll) reacted preferentially at 0-3 with benzoyl or p-toluenesulphonyl diloride in pyridine at -IS C Activation of this position by intramolecular hydrogen bonding is thought to be responsible. ... 

The reaction of dibutyltin oxide with pyranoid m-l,2-diols has attracted interest, since the resulting cyclic dibutylstannylene derivatives are substituted regioselectively at the equatorial oxygen-atom when treated with an acyl chloride or an active alkyl halide. Thus the cyclic dibutylstannylene derivative (332 ... 

Benzylation of the 5-amino-5-deoxy-pentoside 3 via its 2,3-O-dibutylstannylene derivative afforded a 1 1 mixture of the 2-0- and 3-0-benzyl ethers, whereas tritylation and silylation under the same conditions generated predominantly the 2-O-protected derivative. Similarly, benzylation of the D-erythronolactone 4 via its 0-dibutylstannylene derivative gave predominantly the 2-O-benzyl ether 5 while reductive opening (TiCU, HSiEts) of the corresponding 2,3-0-benzylidene compound afforded the 3-0-benzyl ether 6. Partial benzylation (0.9 eq NaH, DMF, BnBr) of sucrose has afforded 42% of 2-0-benzyl-sucrose, isolated as its 3,4,6,r,3, 4, 6 -heptaacetate. The molecular electrostatic potential profile of sucrose apparently predicts that the 2-OH group is the most electropositive of the eight hydroxy-groups. ... 

---