Chemistry Reference
In-Depth Information
trated, and the residue was chromatographed (hexane/ethyl acetate, 5:1) to give 580
mg (33% yield) of the mixed carbonate 928.
CDI
MeOBn-OH
THF
60°C, 16 h
O
O
OH
33 %
927
928
O
BnOMe
I
2
MeCN
I
I
+
O
O
O
O
929
O
O
erythro : threo
6 : 1
4.3.3.6
Acyl Carbonates
An established method for the activation of carboxylic groups, particularly those of
N-protected amino acids or peptides, is to form ''mixed anhydrides'' with alkyl
chloroformates or dialkyl dicarbonates such as Boc
2
O. Acyl carbonates can also be
essential intermediates in the reactions of anhydrides with carbonates.
Di-tert-butyl dicarbonate (Boc
2
O)
A detailed review on the reactions of di-tert-butyl dicarbonate (Boc
2
O), in conjunc-
tion with 4-dimethylaminopyridine (DMAP), with amines and alcohols has been
given by Hassner and Basel [664]. Many general procedures for reactions of Boc
2
O
with common alcohols 930 are presented therein. In most cases, either O-Boc de-
rivatives 933 and/or symmetrical carbonates 934, or mixed 931 and/or symmetrical
carbonic-carbonic anhydrides 932 are formed.
O
O
O
O
+
R
R
R
O
O
O
O
O
O
Boc
2
O
DMAP
carbonic-carbonic anhydrides
931
932
R-OH
MeCN
930
O
O
+
R
R
R
O
O
O
O
carbonates
934
933
