an interesting paper from Eun Lee

A Carbonyl Ylide Cycloaddition Approach to Platensimycin
Lee, Kim, Jang, Choi and Chung. ACIEE, 2008,















why interesting?
"they knew that a terminal olefin would have the incorrect electronic configuration to lead to the desired product in the [3+2] before attempting the chemistry. However, they did the reaction anyway, and ended out with a cracking yield of the wrong isomer and only a trace of the desired. Playing with the HOMO coefficient by using a vinyl halide in place of the terminal olefin allowed the chemistry to proceed in a tasty 83% yield, with small amounts of the competing products."
from http://totallysynthetic.com/blog/?p=976

A proposal to make 7-Methylomuralide

Corey recently published the synthesis of (-)-7-Methylomuralide. very short synthesis. Here is my proposal. Also short, but racemic.

A way to make diazo compounds

From:
jac_2004_126_12222
Michael E. Furrow and Andrew G. Myers*


The bimolecular reaction of carboxylic acids with diazoalkanes
to form esters is among the mildest and most efficient of organic
transformations but is seldom used in synthesis beyond the
important case of methyl esterification.1 This is largely a consequence
of the inaccessibility and poor stability of higher diazoalkanes
as substrates.2 In this work we describe a new method for
the synthesis of diazoalkanes by the oxidation of N-tert-butyldimethylsilylhydrazones
(TBSHs) with (difluoroiodo)benzene,3 a reagent
heretofore unexplored in the context of hydrazone oxidation.
When conducted in the presence of a carboxylic acid substrate,
the oxidation leads to efficient esterification in situ (Scheme 1). In
addition to greatly extending the range of diazoalkanes that are
now available for esterifications, this new protocol offers significant
advantages with regard to safety, for diazo intermediates are neither
isolated nor achieve appreciable concentrations during the reaction.

deprotection/protection of allylether

1. formation of allyl ether.
allylbromide/base

2. deprotection.
1. pdcl2/acoh/Naoac/water. heated to 70C for 2 hr.
works ok, but sometimes cause decomposition of my sugar compound.
2. pd(PPh3)4/acoh, 80C. 2hr.
works great, high yield. rxn started even before heating at rt!