Methyl Tributylstannyl Sulfide


[17314-32-8]  · C13H30SSn  · Methyl Tributylstannyl Sulfide  · (MW 337.15)

(methanethiol equivalent in thioglycoside synthesis)

Physical Data: bp 104 °C/0.2 mmHg; n22D 1.5110.

Solubility: insol H2O; sol hexane, acetone, ether.

Analysis of Reagent Purity: reacts readily with iodine and can be titrated against a solution of iodine in carbon tetrachloride.

Preparative Methods: prepared simply by mixing Bis(tri-n-butyltin) Oxide and Methanethiol followed by distillation under vacuum.1 Preparation from Tri-n-butylchlorostannane and NaSMe is also possible.2

Handling, Storage, and Precautions: due to the low volatility, this reagent is much easier to handle than the parent thiol (MeSH; bp 6 °C). However, in addition to the strong odor, it is highly toxic (as is the case with all organotin compounds) and should be handled and stored accordingly.

Thioglycoside Synthesis.

Methyl tributylstannyl sulfide is widely applicable to the preparation of a variety of thioglycosides which are useful synthetic blocks in oligosaccharide synthesis. For instance, glycopyranosyl bromide or acetate gives the corresponding methylthioglycoside in high yield by the action of Bu3SnSMe in combination with Tin(IV) Chloride.3 In general, glycosyl bromide gives the product as a mixture of anomers, because of the partial anomerization of the initially formed b-thioglycoside catalyzed by some Lewis acidic species generated in situ. Although the transformation from glycosyl bromide can be achieved without SnCl4, the reaction requires higher temperature and results in incomplete conversion. On the other hand, the reaction of glycopyranosyl acetate gives the 1,2-trans product selectively (eq 1). In addition to such stereoselectivity, the ease of preparation and stability makes the use of a glycosyl acetate preferable over the glycosyl bromide as a starting material. A similar reaction using ribofuranosyl acetate gives a mixture of b- and a-anomers (eq 2).

Since it is known that the reaction of such sugar derivatives with free thiols and Zinc Chloride sometimes gives a dithioacetal instead of desired thioglycoside,4 the substitution of hydrogen by a tributylstannyl group seems to attenuate the nucleophilicity of the alkylthio group.

The preparation of complex oligosaccharide-derived thioglycosides is also possible. For this purpose, trichloroacetimidate is the substrate of choice, since it is much more reactive than the corresponding glycosyl acetate (eq 3).5

The use of alkoxystannane (Bu3SnOR) in place of tributylstannyl sulfide gives O-glycosides under similar conditions.6

Thioglycosides in Oligosaccharide Synthesis.

Thioglycoside linkages are stable under acidic and basic conditions, which are usually encountered in carbohydrate manipulations such as protection-deprotection of hydroxy groups. In spite of such stability, thioglycosides are powerful glycosyl donors under certain conditions and are widely used in oligosaccharide synthesis (examples7). Numerous methods are now available to activate alkylthioglycosides. Some examples of promotors are as follows: MeOSO2CF3,8 PhHgOSO2CF3,9 Me2SSMe+CF3SO2-,10 CuBr2-Bu4NBr,11 PhSeCl-AgOSO2CF3,12 MeSBr-AgOSO2CF3,13 NIS-CF3SO3H,14 AgOSO2CF3-Br2.15

1. Peach, M. E. CJC 1968, 46, 211.
2. Abel, E. W.; Brady, D. B. JCS 1965, 1192.
3. Ogawa, T.; Matsui, M. Carbohydr. Res. 1977, 54, C17.
4. Wolfrom, M. L.; Thompson, A. JACS 1934, 56, 1804. Wolfrom, M. L.; Whiteley, T. E. JOC 1962, 27, 2109.
5. Goto, F.; Ogawa, T. PAC 1993, 65, 793.
6. Ogawa, T.; Matsui, M. Carbohydr. Res. 1976, 51, C13.
7. Fügedi, P.; Birberg, W.; Garegg, P. J.; Pilotti, &AAring;. Carbohydr. Res. 1987, 164, 297.
8. Lönn, H. Carbohydr. Res. 1985, 139, 105.
9. Garegg, P. J.; Henrichson, C.; Norberg, T. Carbohydr. Res. 1983, 116, 162.
10. Andersson, F.; Fügedi, P.; Garegg, P. J.; Nashed, M. TL 1986, 27, 3919.
11. Sato, S.; Mori, M; Ito, Y.; Ogawa, T. Carbohydr. Res. 1986, 155, C6.
12. Ito, Y.; Ogawa, T. TL 1988, 29, 1061.
13. Dasgupta, F.; Garegg, P. J. Carbohydr. Res. 1988, 177, C13.
14. Veeneman, G. H.; van Leeuwen, S. H.; van Boom, J. H. TL 1990, 31, 1331.
15. Kihlberg, J. O.; Leigh, D. A.; Bundle, D. R. JOC 1990, 55, 2860.

Yukishige Ito & Tomoya Ogawa

The Institute of Physical and Chemical Research (RIKEN), Saitama, Japan

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