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Total Synthesis of (+)‐Hyacinthacine A 1 , (+)‐7a‐ epi ‐Hyacinthacine A 1 , (6 R )‐6‐Hydroxyhyacinthacine A 1 and (6 S )‐6‐Hydroxy‐7a‐ epi ‐hyacinthacine A 1
Author(s) -
D'Adamio Giampiero,
Goti Andrea,
Parmeggiani Camilla,
MorenoClavijo Elena,
Robina Inmaculada,
Cardona Francesca
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201101096
Subject(s) - chemistry , nitrone , deoxygenation , total synthesis , cycloaddition , stereochemistry , organic chemistry , catalysis
The total synthesis of natural (+)‐hyacinthacine A 1 ( 6 ), (+)‐7a‐ epi ‐hyacinthacine A 1 ( 7 ) and their 6‐hydroxy analogues 21 and 16 was achieved using a nitrone cycloaddition strategy with D ‐ribose‐derived cyclic nitrone 8 as the dipole and tert ‐butyl acrylate as the dipolarophile. After separation of the adducts, reductive cleavage of the N–O bond followed by lactam reduction and deprotection afforded the two non‐natural hydroxy analogues in excellent yields. The synthesis of (+)‐hyacinthacine A 1 ( 6 ) and of (+)‐7a‐ epi ‐hyacinthacine A 1 ( 7 ), which required deoxygenation at C(6), was accomplished by DIBAL‐H reduction of mesylate derivatives of the pyrrolizidinols 20 and 15 , respectively. Evaluation of the synthesized compounds against a panel of 12 commercially available glycosidases showed that hyacinthacine A 1 ( 6 ) and its (6 R )‐hydroxy analogue 21 are good inhibitors of amyloglucosidase; the non‐natural compound 21 is also a strong inhibitor of β‐glucosidase, while 6 showed only moderate inhibition. The non‐natural (+)‐7a‐ epi ‐hyacinthacine A 1 ( 7 ) is a moderate inhibitor of amyloglucosidase and α‐ L ‐fucosidase; the presence of the (6 S )‐hydroxy group in 16 led to diminished activity.