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Biologically active glycosides from asteroidea, XXVII. Stereochemistry of the C‐17 side chain of 26‐homothornasterol B: Novel triethylaluminum‐promoted rearrangement and alkylation of epoxy alcohols
Author(s) -
Honda Masanori,
Igarashi Takashi,
Marubayashi Nobuhiro,
Komori Tetsuya
Publication year - 1991
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.1991199101108
Subject(s) - chemistry , epoxide , alkylation , side chain , aldol reaction , stereochemistry , derivative (finance) , glycoside , organic chemistry , catalysis , financial economics , economics , polymer
The absolute configuration of 3,6‐di‐ O ‐acetyl‐26‐homothornasterol B ( 3 ) obtained previously besides the 3,6‐di‐ O ‐acetyl derivative ( 2 ) of (20 S ,24 S )‐24‐ethylthornasterol A by aldol reaction 2a) of the mixture of (3 S )‐3‐ethyl‐4‐methyl‐2‐(trimethylsiloxy)‐1‐pentene ( 7 ) and 3,4‐dimethyl‐2‐(trimethylsiloxy)‐1‐hexene ( 8 ) with (+)‐diacetylasterone ( 1 ) has been determined by X‐ray structural analysis as (20 S ,24 S ,25 R )‐3β,6α‐diacetoxy‐20‐hydroxy‐24‐methyl‐26‐homo‐5α‐cholest‐9(11)‐en‐23‐one. On the basis of these results a novel rearrangement and alkylation of the epoxy alcohols 6, 9, 13 , and 15 with triethylaluminium have been discovered and investigated. The reaction occurs when the C‐4 position adjacent to the epoxide ring is congested.