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!

Swern oxidation typical procedure

Procedure: 25 mL 1-neck flask, stirbar, septum, N2 inlet

Dissolved 0.077 mL of oxalylchloride (II) in 4.0 mL of dry CH2Cl2. Stirred; cooled to -78 C. Added 0.125 mL of DMSO. Stirred 10 min. Added a solution of 0.096 g of alcohol I in 1.0 mL of CH2Cl2. Stirred 15 min. Added 0.250 mL Et3N. After 15 min, warmed to 0 C. After 10 min TLC showed complete reaction. The reaction mixture was placed on a silica gel column and the product was isolated by flash chromatography .

notes

1. temp is critical for high yielding.
2. other than oxalylchloride, many activator can be used to overcome problem caused by oxalylchloride (ex. Cl-), ex. P2O5.


cited from
http://www.alsnotebook.com/oxidswern.html

an approach to Actinophyllic Acid

This synthesis plan was made by me about half a year before Overmann's beautiful synthesis of the same molecular.

An approach to Sordaricin

This proposal is just another application of carbene chemistry in the total synthesis of natural products.