A Carbohydrate Approach to the Enantioselective Synthesis of 1,3-Polyols.
Treatment of per-O-benzoyl-D-glycero-D-gulo-heptono-1,4-lactone (2) with tertiary amines afforded selectively and with good yields the (5H)-furan-2-one derivatives 3, 4, and 5, formed by controlled elimination of one, two, or three molecules of benzoic acid, respectively. The stereochemistry for the exocyclic double bonds of 4 and 5 was determined by means of NMR techniques. Particularly, the furanone 4 was obtained from 2 ( approximately 90% yield) as a mixture of the E and Z diastereoisomers, which were separated by column chromatography or, more efficiently, by HPLC. The catalytic hydrogenation of compounds 4-E and 4-Z took place diastereoselectively, due to the chiral induction of the stereocenter located in the lateral chain. Thus, hydrogenation of 4-E led to a mixture of the 4,5-dihydro-(3H)-furan-2-ones having 3R,5S,2'S (D-xylo, 6) and 3S,5R,2'S (D-arabino, 7) configurations, with 6 as the major product; whereas the 4-Z isomer gave the same mixture, but being 7 preponderant. On hydrogenation of the original 4-E/Z mixture, compound 6 was obtained pure after recrystallization. O-Debenzoylation of 6gave 9, which was reduced with NaBH(4) to the 3,5-dideoxy-meso-xylo-heptitol (11). The peracetate (12) and perbenzoate (13) of the latter were prepared, and the 1-(tert-butyldiphenylsilyl)oxy derivative (16) was also synthesized via the 3'-(silyloxy)-4,5-dihydro-(3H)-furan-2-one 14. Chemoselective reduction of the lactone function of 6 with diisoamylborane gave the 2,5,6-tri-O-benzoyl-3,6-dideoxy-D-xylo-heptofuranose (17). The 3,5-dideoxy-D-arabino-heptitol (18), a diastereoisomer of 11, was also isolated and characterized.
Di Nardo
Christián
C
Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428, Buenos Aires, Argentina.
Jeroncic
Lucio O.
LO
de Lederkremer
Rosa M.
RM
Varela
Oscar
O