Synthesis of naturally occurring PDglucopyranoside10

The synthetic P-D-glucopyranoside 30 was converted to the cyanoglucoside rho-diocyanoside A (38a), which was isolated from the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey. (Crassulaceae) and found to show antiallergic activity in a passive cutaneous anaphylaxis test in rat. Acetylation of 30 gave an acetate (98% yield) which was subjected to ozonolysis to afford the aldehyde 39. The Horner-Emmons reaction of 39 using diethyl (1-cyanoethyl)phosphonate furnished (Z)-40a (32% yield from 30) and (E)-40b (10% yield from 30). The physical

Synthesis of naturally occurring (-D-glucopyranosides and analogs (under kinetic condition)

Synthesis of naturally occurring (-D-glucopyranosides and analogs (under kinetic condition)

Entry ROH (eq)

(-Glucosidase/ buffer (U ml)-1

Entry ROH (eq)

(-Glucosidase/ buffer (U ml)-1

Me2C=CHCH2OH (1) CH2 =C(Me)CH2OH (1) HOCH2CH(OBn)CH2OH (1)

glu-OCH2CH=CMe2

glu-OCH2C(Me)=CH2

glu-OCH2CH(OBn)CH2OH

glu-OC10H15

glu-OC10H15

data of (Z)-40a were identical with those (*H- and 13C-NMR) of the reported (Z)-40a. Deprotection of (Z)-40a and (E)-40b provided the (-D-glucosides 38a (77% yield) and unnatural 38b (87% yield), respectively. The physical data ([a]D*H- and 13C-NMR) of the synthetic 38a were identical with those ([a]D, *H- and 13C-NMR) of the natural rhodiocyanoside A (38a) (Fig. 4).

The synthetic 31 was converted to the cyanoglucoside osmaronin (41a) which was isolated from a methanolic extract of the leaves of Osmaronia cerasi-formis. Acetylation of 31 gave an acetate (99% yield) which was subjected to ozonolysis to afford a ketone 42. The Horner-Emmons reaction of 42 using diethyl cyanomethylphosphonate furnished (Z)-43a (22% yield from the acetate of 31) and (E)-43b (10% yield from the acetate of 31). Deprotection of (Z)-43a and (E)-43b gave the (-D-glucosides 41a (83% yield) and 41b (94% yield), respectively. The spectral data of the synthetic 41a were identical with those (*H- and 13C-NMR) of the natural osmaronin (41a) (Fig. 5).

Figure 4: Synthesis of rhodiocyanoside A.

HOH2q

HO HO

O Me

- AcOH2C

43a CN

0H 41b

Osmaronin41a CN

(a); (1) Ac20/pyridine (2) 03 (3) Me2S (b); (Et0)2P(0)CH2CN/NaH/THF (c); K2C03/Me0H Figure 5: Synthesis of osmaronin.

Then the synthetic 32 was converted to the cyanoglucoside sutherlandin (44) which was isolated from leaves of Acacia sutherlandii. Acetylation of a diastereomeric mixture of 32 gave the corresponding acetate which was subjected to the hydrogenation and the subsequent oxidation to yield the a-acetoxyl ketone (45, 84% overall yield from the acetate of 32). The Horner-Emmons reaction of 45 using diethyl cyanomethylphosphonate furnished (Z)-46a (33% yield from 45) and (E)-46b (31% yield from 45). Deprotection of the presumably desired (Z)-46a afforded (Z)-44 (76% yield), whose 13C-NMR spectra were identical with those of the natural sutherlandin (44) (Fig. 6).

Figure 6: Synthesis of sutherlandin.

Was this article helpful?

0 0

Post a comment