The advantage of “arming” and “disarming” glycosyl donors lies in their synthetic use. By disarming the glycosyl, a selective coupling can be achieved. The disarmed portion of the disaccharide can then be armed through selective deprotection. The disaccharide can then be coupled to a disarmed sugar. This process can be repeated as many times as necessary to achieve an efficient synthesis of a desired oligosaccharide with minimal loss of material to undesired coupling. This can be especially useful in “one-pot” synthetic methods. In these methods, multiple sugars are added to the reaction mixture. One of the sugars is armed as the glycosyl donor, and reacts quickly with a glycosyl acceptor. The non-reducing sugar then acts as a glycosyl acceptor as a protecting group that is easily lost in solution reveals a free hydroxyl group. This reacts with a donor that was disarmed, forming the oxocarbenium ion at a slower rate, producing the desired trisaccharide.