Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes. Part 17: Synthesis and opening reactions of cis- and trans-oxides derived from (2S,6R)-2-benzyloxy-6-methyl-3,6-dihydro-2H-pyran, (2R,6R)- and (2S,6R)-2-methoxy-6-methyl-5,6-dihydro-2H-pyran

Tetrahedron

Volumn 58, Issue 30, 2002, Pages 6069-6091

  Crotti, Paolo ^a   Di Bussolo, Valeria ^a   Favero, Lucilla ^a   Macchia, Franco ^a   Pineschi, Mauro ^a  

^a UNIVERSITY OF PISA   (Italy)

Author keywords

Deoxy anhydrosugars; Epoxides; Opening reactions; Regioselectivity

Indexed keywords

2 BENZYLOXY 6 METHYL 3,6 DIHYDRO 2H PYRAN; 2 METHOXY 6 METHYL 5,6 DIHYDRO 2H PYRAN; CARBOHYDRATE DERIVATIVE; EPOXIDE; ETHYLENE OXIDE; GLUCOPYRANOSIDE; METHYL GROUP; OXIDE; PYRAN DERIVATIVE; UNCLASSIFIED DRUG;

ACETYLATION; ARTICLE; CHELATION; ENANTIOMER; ENANTIOSELECTIVITY; HYDROLYSIS; PRIORITY JOURNAL; RING OPENING; STEREOCHEMISTRY; STEREOISOMERISM; SYNTHESIS;

EID: 0037157815     PISSN: 00404020     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4020(02)00578-1     Document Type: Article

References (45)

1. (a) Crotti P., Di Bussolo V., Favero L., Macchia F., Pineschi M. Eur. J. Org. Chem. 1998;1675-1686. and references therein.
2. (b) Calvani F., Crotti P., Gardelli C., Pineschi M. Tetrahedron. 50:1994;12999-13021
3. (c) Crotti P., Di Bussolo V., Favero L., Pineschi M., Marianucci F., Renzi G., Amici G., Roselli G. Tetrahedron. 56:2000;7513-7524.
4. Crotti P., Di Bussolo V., Favero L., Jannitti N., Pineschi M., Pasero M. Gazz. Chim. Ital. 127:1997;79-90.
5. Martin A., Païs M., Monneret C. Carbohydr. Res. 113:1983;189-201.
6. 4 in MeCN).
7. The cis/trans descriptors preceding the number for each epoxide indicate the relative configuration between the oxirane ring and methyl group (first descriptor) and the OR group (R=Me or benzyl) (second descriptor), respectively.
8. The indifferent use of benzyl or methyl glycosides as derivatives of epoxides 3-8 is dictated by the consideration that the nature of the acetal group should not reasonably influence the stereo- and regiochemical behavior of these epoxides.
9. (a) Fraser-Reid B., Kelly D.R., Tulshian D.B., Ravi P.S. J. Carbohydr. Chem. 2:1983;105-114.
10. (b) Brimacombe J.S., Da'Aboul I., Tucker L.C.N. Carbohydr. Res. 19:1971;276-280
11. (c) Schou C., Pedersen E.B., Nielsen C. Acta Chim. Scand. 47:1993;889-895.
12. Shelton J.R., Cialdella C. J. Am. Chem. Soc. 23:1958;1128-1133.
13. (a) Lawton B.T., Szarek W.A., Jones J.K.N. Carbohydr. Res. 14:1970;255-258
14. (b) Capek K., Jary J. Collect. Czech. Chem. Commun. 35:1970;1727-1732
15. (c) Paulsen H., Sumfleth B., Redlich H. Chem. Ber. 109:1976;1362-1368
16. (d) Ohta K., Miyagawa O., Tsutsui H., Mitsunobu O. Bull. Chem. Soc. Jpn. 66:1993;523-535
17. (e) Szarek W.A., Vyas D.M., Gero S.D., Lukacs G. Can. J. Chem. 52:1974;3394-3400.
18. 9e which turned out to be difficult to separate.
19. (a) Bauer T. Tetrahedron. 53:1997;4763-4768.
20. (b) Kefurt K., Kefurtová Z., Jary J. Collect. Czech. Chem. Commun. 40:1975;164-173.
21. (c) Tsutsui H., Mitsunobu O. Tetrahedron Lett. 25:1984;2159-2162.
22. Brandstetter H.H., Zbiral E. Helv. Chim. Acta. 63:1980;327-343.
23. In search of a stereoselective synthesis of epoxide (+)-7, the diacetoxy derivative (+)-39α was checked in mono-deprotection procedures in order to get the monoacetate 40α, regioselectively. Unfortunately, the best result obtained (lipase PPL, phosphate buffer, pH 7) afforded a mixture of monoacetates 34α and 40α showing a regioselectivity (60%) towards the monoacetate 40α, necessary for the synthesis of epoxide (+)-7, lower than the corresponding regioselectivity (85%) towards monotosylate 37, found in the monotosylation of diol (+)-31α, which leads to epoxide (+)-7, as well.
24. 15b and show the non-applicability of this procedure to an effective synthesis of diol (-)-31β and, consequently of epoxides (-)-5 and (-)-6 ( Scheme 5 ).
25. (a) Mathlouthi M., Maciejewski C., Serghat S., Hooft R.W.W., Kanters J.A., Kroon J. J. Mol. Struct. 291:1993;173-182.
26. (b) Dean D.M., Szarek W.A., Jones J.K.N. Carbohydr. Res. 33:1974;383-386. and references therein.
27. (a) Garegg P.J., Johansson R., Ortega C., Samuelsson B. J. Chem. Soc., Perkin Trans. 1. 1982;681-683
28. (b) Wessel H.P., Viaud M.-C., Gardon V. Carbohydr. Res. 245:1993;233-244.
29. Paulsen H., Rutz V., Brockhausen I. Liebigs Ann. Chem. 1992;747-758.
30. - on the β face of the intermediate oxonium ion 41, reacting through its conformer 41″ (route a). However, as tentatively shown in the following scheme, this attack turns out to be particularly unfavored because suffering from an 1,3-syn diaxial interaction with the methyl and the AcO groups in C(5) and C(3), respectively. See: (a)
31. - on the β face of the intermediate oxonium ion 41, reacting through its conformer 41″ (route a). However, as tentatively shown in the following scheme, this attack turns out to be particularly unfavored because suffering from an 1,3-syn diaxial interaction with the methyl and the AcO groups in C(5) and C(3), respectively. See: (a) Sayer J.M., Yagi H., Silverton J.V., Friedman S.L., Whalen D.L., Jerina D.M. J. Am. Chem. Soc. 104:1982;1972-1978. and references therein.
32. For related considerations in the cyclohexane system see: (b) Eliel E.L., Allinger N.J., Angyal S.J., Morrison G.A. Conformational Analysis. 1965;Wiley, New York. pp 307-314 (c) Eliel E.L., Wilen S.H. Stereochemistry of Organic Compounds. 1994;Wiley, New York. pp 729-730.
33. Szarek W.A., Zamojski A., Gibson A.R., Vyas D.M., Jones J.K.N. Can. J. Chem. 54:1976;3783-3793.
34. Note the completely different regioselectivity observed with anomeric diols (+)-31α and (-)-31β when subjected to monoacetylation in the presence of lipase PS: selective protection of the C(2)-OH in the case of (+)-31α and of the C(3)-OH in the case of (-)-31β. Evidently, the axial (in 31α) or equatorial direction (in 31β) of the acetal -OMe group plays an important role in favoring or disfavoring the reactivity of the equatorial C(2)-OH group, respectively.
35. Epoxides 5 and 6 have been previously described as a racemic mixture: Berube G., Luce E., Jankowski K. Bull. Soc. Chim. Fr. 1983;109-111.
36. In the α-series, the C(3)-OH selectivity observed under Mitsunobu operating conditions led to the epoxide (+)-8, also obtained through the long monoacetylation-mesylation-saponification-cyclization procedure starting from diol (+)-31α. On the contrary, in the β-series, as a result of the opposite selectivity obtained in the lipase PS-catalyzed monoacetylation of diol (-)-31β, the Mitsunobu protocol leads to epoxide (-)-6, the diastereoisomer of epoxide (-)-5 obtained through the alternative long sequence.
37. Alcohol (±)-47 was prepared by an hetero Diels-Alder cycloaddition between Danishefsky diene (45) and acetaldehyde. The obtained dihydropyranone (±)-46 is reduced by DIBAL to the desired alcohol (±)-47 ( Scheme 6 ). See: Danishefsky S., Kerwin J.F. Jr. J. Org. Chem. 47:1982;1597-1598. and references therein.
38. The absence in the reaction mixture of products possessing an inverted configuration at C(2) (a manno configuration) reasonably rules out the formation of the diastereoisomeric β-epoxide in the oxidation of glycal (±)-48, in agreement with the sensitiveness of the DMDO to steric effects. Accordingly, the attack of the DMDO occurs on the less hindered α-face, opposite the β-direction of the substituents present in C(3) and C(5), to give α-epoxide (±)-49α, as observed.
39. (a) Crotti P., Di Bussolo V., Favero L., Macchia F., Pineschi M. Gazz. Chim. Ital. 127:1997;273-275.
40. (b) Schaus S.E., Bránalt J., Jacobsen E.N. J. Org. Chem. 63:1998;403-405.
41. 2,3.
42. Also in the few cases in which the opening reactions under standard conditions are not completely C-3 stereoselective, the corresponding results under chelating conditions show an increase or the only presence of C-3 products, in accordance with the rationalization given.
43. 2.
44. Actually, it is not clear why epoxide 6 is not sensitive, to some extent, to different operating conditions as diastereoisomeric epoxide 8 is.
45. 2 determine only a slight increase of C-2 regioselectivity ( Table 2, entries 33 and 34).