Angewandte
Chemie
=
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of the C1 azide and esterification of the C34 carboxylic acid.
Introduction of tBu to 55 with 56[31] and subsequent treatment
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1
57 showed H NMR data that was identical to that provided
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In summary, we have reported the formal total synthesis
of (+)-pinnatoxin A in a highly convergent fashion. The
salient methodologies employed in our successful campaign
include 1) stereoselective bis-acetalization to yield the BCD-
ring fragment 2 effected by exploiting intramolecular hydro-
gen bonding; 2) intramolecular alkylation of epoxynitrile 4 to
construct the G-ring; 3) powerful dithiane coupling to unify
the two halves of the molecule (2 and 3); 4) macrocyclization
of 27-membered carbocycle 46 by utilizing olefin metathesis
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Received: August 27, 2004
Keywords: heterocycles · macrocycles · natural products ·
spiro compounds · total synthesis
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[14] Existence of this intramolecular hydrogen bond was suggested
from the X-ray analysis of a closely related substrate with free
hydroxy groups at C10 and C24.[4a] Furthermore, acidic treat-
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formation of the desired spiroacetal and its C19-epimer despite
the seemingly favorable anomeric effect at C19 of the desired
compound.
.
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