Synthesis of 3Zhexenyl 6OPDxylopyranosylPDglucopyranoside

The tert-butyldimethylsilyl (TBDMS) protection of 50 gave a silyl ether

(77) in 60% yield, which was subjected to consecutive benzoylation and deprotection of the TBDMS group to give the desired (3Z)-hexenyl 2,3,4-tri-O-benzoyl-P-D-glucopyranoside (78) in 80% yield (two steps). On the other hand, 2,3,4-tri-O-benzoyl-a-D-xylopyranosyl bromide was prepared by literature procedures. The alcohol (78) was treated with 2 equivalents of 2,3,4-tri-O-benzoyl-a-D-xylopyranosyl bromide in the presence of AgOTf and TMU in CH2Cl2 to give the corresponding coupling product (79) in 69% yield. Finally, treatment of 79 with NaOMe in MeOH-THF provided the synthetic (3Z)-hexenyl 6-O-Pvxylopyranosyl-P-D-glucopyranoside (74) in 85% yield.

(3Z)-Hexeriyl 6-O-p-o-xylopyranosyl-p-D-glucopyrarioside (74)

(3Z)-Hexenyl 6-O-a-L-arabinopyranosyl-p-D-glucopyranoside (75)

(3Z)-Hexenyl 6-O-a-L-rhamnopyranosyl-p-D-glucopyranoside (76)

Figure 14: Synthesis of naturally occurring (3Z)-hexenyl P-D-glucopyranosides.

3.5.2. Synthesis of (3Z)-hexenyl 6-O-a-L-arabinopyranosyl-fi-D-glucopyranoside (75)

The coupling reaction of 78 and 2 equivalents of the known 2,3,4-tri-O-benzoyl-a-L-arabinopyranosyl bromide in the presence of AgOTf and TMU in CH2Cl2 gave the coupled product (80) in 68% yield. Finally, treatment of 80 with NaOMe in MeOH-THF provided the synthetic (3Z)-hexenyl 6-O-a-L-arabinopyranosyl-P-D-glucopyranoside (75) in 83% yield.

3.5.3. Synthesis of (3Z)-hexenyl 6-O-a-L-rhamnopyranosyl-fi-D-glucopyranoside (76)

The coupling reaction of 78 with 2 equivalents of the reported 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl bromide in the presence of AgOTf and TMU in CH2Cl2 gave the coupled product (81) in 56% yield. Finally, treatment of 81 with NaOMe in MeOH-THF provided the synthetic (3Z)-hexenyl 6-O-a-L-rhamnopyranosyl-P-D-gluco-pyranoside (76) in 96% yield.

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